&EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1336
Protection Agency
Stratospheric Ozone Protection
Methyl Bromide Alternatives
10 Case Studies Vol. II
Foreword
This is the second EPA publication of case studies describing alternatives to the pesticide
methyl bromide. As with the first volume of case studies, the alternatives listed here were
chosen because of their level of development and availability, and should not be construed to be
the only alternatives to methyl bromide.
It is now clear that methyl bromide is a significant stratospheric ozone depleting chemical,
and agricultural use of this material contributes to environmental degradation. Because of this,
methyl bromide will soon be phased out both in the United States and internationally. This
pesticide has been used since the early 1960's, primarily as a pre-plant soil fumigant (often for
high-value crops such as strawberries and tomatoes), as well as a post-harvest (commodity) and
structural treatment.
EPA recognizes the importance of a pest control agent like methyl bromide to the
agricultural community. Since effective pest management is essential to field agricultural
production, commodity storage, natural resource protection, and public health, alternatives to
methyl bromide which are efficacious, cost effective, and environmentally sound must be
available before methyl bromide is phased out. To assist in this effort, EPA has published this
document, as well as the first set of case studies, and has committed to publish two more
volumes of case studies.
The alternative materials and methods discussed in these case studies are not intended
to be complete replacements for methyl bromide, but tools which are efficacious against the
pests that are currently controlled by this pesticide. Many of the alternatives described herein are
part of an overall integrated pest management system, and must be combined with other pest
control tools to achieve an economically viable level of management. The individual elements
are considered in these case studies as a way to define and characterize the wide array of
alternatives to methyl bromide.
All efforts were made to insure that the information in this document is correct and
factual. Comments on this document, as well as your experiences with these and other
alternatives to methyl bromide, are welcome via the contacts listed below.
For additional information, please contact:
Ozone Protection Hotline tolf4ree (800) 296-1990
Bid f harms, Methyl Bromide Program
U.S, EPA~6205J,401 M Street S.W.; Washington, DC 20460
TEL: 202-233-9179, FAX: 202-233-963?
E-MAIL: thomas.bill@epamaSLepa.gov
EPA JVtethyl Bromide Phase-Out Web Site:
This publication discusses specific proprietary products and pest control methods. Some of these alternatives are now commercially available,
while others are in an advanced stage of development In all cases, the information presented does not constitute a recommendation or an
endorsement of these products or methods by the Environmental Protection Agency (EPA) or other involved parties. Neither should the
absence of an item or pest control method necessarily be interpreted as EPA disapproval.
-------
-------
vxEPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1996
Protection Agency
Stratospheric Ozone Protection
Methyl Bromide Alternatives y^-=*ay
10CaseStudiesVol.il fO
Table of Contents
Soil Use:
Nematode Resistant Cultivars
(hloropicrin in Strawberry Production
Organic Strawberry Production
Soil polarization
Soil polarization in Orchards
IPM in California Vineyards
Commodity Use:
Heat Treatments for Perishable Commodities
Heat Treatments for Timber
Irradiation
Structural Use:
Sulftiryi fluoride
Note: Page numben have teen purposely excluded from ttiii document to allow individual case studies to be copies and distributed.
-------
-------
-EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
December 1996
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Using Nematode Resistant Cultivars As An Alternative to Methyl Bromide for Selected Crops
Nematode resistant cultivars can be used as part of an integrated approach to develop an effective alternative to
methyl bromide against a wide variety of nematodes for a wide variety of crops, particularly high value vegetable and
fruit commodities. Crops for which both nematode resistant cultivars have been developed and for which methyl
bromide has been used include both seed crops (tomatoes, bell and hot peppers, and tobacco) and vineyard/orchard
crops (grapes, peaches, plums, apricots and nectarines, walnuts, almonds, and citrus) (Slaughter 1996, Fortnum 1996,
Noling 1996, McKenry and Kretsch 1995, Thies et al. 1995, Khan and Khan 1991, Lehman and Cochran 1991, Cook
and Evans 1987).
Nematode resistant cultivars have a number of
distinct non-commodity-specific advantages over the use of
methyl bromide, including 1) complete prevention of
nematode reproduction, 2) no requirements for special
application techniques or equipment, and 3) comparable costs
to non-resistant cultivars. Nematode resistant cultivars are
particularly effective because they can be used in conjunction
with other pest control practices (i.e., sanitation, soil
solarization, soil amendments (compost and manure),
biological control, crop rotation, and early planting scheduling
to reduce or eliminate nematode infestation (Dunn 1993,
Lehman and Cochran 1991, Cook and Evans 1987).
Benefits of Nematode Resistant Cultivars
^ Reduces the need for methyl bromide
^ Prevents nematode reproduction
^ Requires no special application techniques
or equipment
' Comparable costs to non-resistant cultivars
^ Can be used in conjunction with other pest
control practices
Nematodes
Nematodes (microscopic unsegmented roundworms) are defined as any member of the Phylum Nematoda,
including those that are parasitic to plants and animals. Plant parasitic nematodes are extremely common in soil, where
they live primarily in a film of water which surrounds soil particles. A single gram of top soil can contain over one
thousand of these tiny organisms. Nematodes generally interfere with water/nutrient availability and a plant's feeding
mechanisms (i.e., root function and plant growth processes) (Ashwroth 1991). Many species of nematodes exist, and
they attack an enormous variety of plant species. The most common are the root knot nematodes, Meloidogyne
arenaria, Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne hapla. Root knot nematodes alone have a
host range of over 2,000 plants (McKenry and Roberts 1985).
The response of plants to nematode infestation varies considerably according to the species of nematode/
plant and environmental conditions such as host status, soil temperature/moisture/structure, aeration, organic matter,
fertility level, nutrients, nematode predators/parasites, etc. (Gaur and Seshadri 1986). Symptoms of nematode-
damaged plants are generally non-specific and are characterized by poor growth, plant stunting (through the presence
of root galls), crop patchiness, wilting, and chlorosis (yellowing or discoloration of leaves). As a result, preliminary
examination of the crop usually does not provide unequivocal diagnosis of nematode damage. For example, plant
symptoms indicative of nematode infestation can also result from other variables, such as low or excess fertilizer, low
water holding capacity, or poor drainage of soil. Furthermore, plant symptoms in the field may be widespread or
patchy, depending on differences in the nematode densities in the field or the placement of infested planting stocks
(Lehman and Cochran 1991, McKenry and Roberts 1985). Plants stunted or diseased by nematode related activity
may not die, but are likely to produce reduced yields (Hauge and Gowen 1987, McKenry 1987). Plant deaths are
-------
generaUy"hot attributed directly to nematode damage, but instead to secondary pathogens (i.e., fungi and bacteria),
which invade plants weakened by nematodes (McKenry and Roberts 1985).
Outlook for Nematode Resistant Cultivars as a Replacement for Methyl Bromide
Plant breeders have developed nematode resistant cultivars in an effort to prevent the stunted growth and
deformed or galled roots of plants commonly infested with nematodes. Cultivars are defined as cultivated plants
which are produced by breeding programs and are distinguished by characteristics significant for agriculture, forestry,
or horticulture, and which, when reproduced, retain their distinguishing characteristics (Lehman and Cochran 1991,
Cook and Evans 1987). Level of resistance describes the effect of the host on nematode reproduction. A completely
resistant plant allows no nematode reproduction, non-resistant or susceptible plant allows nematodes to multiply
freely, and partially resistant plants support intermediate levels of reproduction (Cook and Evans 1987). Nematode
resistant cultivars are plants bred specifically to inhibit nematode reproduction and resist the impact of nematodes on
plant growth and production, while nematode resistant vineyard and orchard crops also can be developed by grafting
high yield cultivars to resistant rootstocks (Titts 1996). Ideally nematode resistance cultivars are bred for both
resistance (suppressed nematode reproduction) and tolerance (nematode feeding will have little impact on plant
growth and crop yield).
Resistant cultivars are already widely used for specific crops in the United States, particularly in California
and Florida. No fruit or vegetable nematode resistant cultivars are resistant to all nematodes; however, many have
resistance to the most common nematodes, and often in combination with resistance to one or more other pathogens.
If they are otherwise suitable, nematode resistant cultivars are typically planted when no nematicide is used, but are
desirable even when other chemical treatments are used (Dunn 1993). Crops where pre-plant fumigation with methyl
bromide is used and nematode resistance cultivars developed include both seed crops (tomatoes, bell and hot peppers,
and tobacco) and vineyard/orchard crops (grapes, peaches, plums, apricots, nectarines, walnuts, almonds, and citrus).
Crops frequently fumigated with methyl bromide for which there are no nematode resistant cultivars in significant
commercial use to date include: eggplant, cucurbits, carrots, broccoli, cauliflower, melons, and strawberries (Becker
1996). However, currently there are significant research efforts underway to develop nematode resistant cultivars for
many of these crops. For example, Scientists at North Carolina State University have tested five cultivars of
cucumber for resistance to root knot nematodes, these cultivars (C. metuliferus and 'Sumter') account for
approximately 12% of the cucumber crop grown annually in North Carolina. Preliminary results indicate that the
cultivars vary in their resistance to the four root-knot nematode species (Wehner et al. 1991). Likewise, Canadian
scientists are conducting research on the resistance and tolerance of strawberry cultivars to the lesion nematode,
Pratylenchus penetrans (Potter 1995).
Costs
Currently, a large percentage of crop production where nematode resistance has been commercialized utilizes
nematode resistant cultivars (e.g., up to 90 percent for seed crops, 95-100 percent for orchard crops, and 70-85 percent
for vineyards), often in conjunction with pre-plant methyl bromide fumigation. For these crops, gains in plant vigor and
yield have been achieved through use of resistant cultivars. Applications of methyl bromide are utilized in order to
protect the crop from competition from weeds, diseases from fungi, and damage caused by non-susceptible nematode
species. For crops where nematode resistant technology is currently not available, development and commercialization
of resistant cultivars, as part of an integrated system utilizing substitute fumigants (e.g., metam sodium) or non-chemical
alternatives (e.g., solarization), may enable growers to achieve yields currently realized under production systems
utilizing methyl bromide fumigation. It should be noted that other pests, such as weeds, will need to be managed on an
as needed basis, which may add costs to both resistant and non-resistant crop production.
Production costs under a system that uses nematode resistant cultivars in conjunction with an alternative
fumigant can be compared to a system that utilizes methyl bromide with no crop resistance (table 1). A comparison of
these cost estimates is provided in Table 1. Although the cost of resistant cultivars may be slightly higher, yield
increases and lower fumigant treatment costs may help to offset these increases. Furthermore, the costs of nematode
resistant cultivars are expected to decrease in the future as a wider variety of cultivars become available on the
commercial market. In addition, there are other financial benefits of nematode resistant cultivars including cost savings
from growing crops on land most suited to their production (rather than letting the presence of nematodes in a field be
the deciding factor for which crops to grow). Finally, through breeding for resistance, seed producers are also able to
-------
combine resistance with other traits including better marketability, longer shelf life, and increased yields. (Seals 1996,
McKenry 1996, Slaughter 1996, Titts 1996, Emershad 1996, Cook and Evans 1987, Cotton 1996).
More research dedicated to the future development of nematode resistant cultivars is needed. The successes
in the development of nematode resistant cultivars discussed earlier in this document are promising; however, more
varied nematode resistant cultivars must be developed in order for this practice to develop into a broadly applicable
alternative to methyl bromide.
Table 1. Comparative Costs of Resistant versus Non-Resistant Cultivars
Cost Factors
Treatment Cost
Cultivar Costs"
Total
Treatment #h
Alternative Ftimigant"/
Resistant CuJtivwr
($/acre)
750-1,000
50-1,000°
1,050-1,750
Treatment #2;
M*^»yiBiro»nide/
Hoa-Resistant Cuftrvar
($/»«*«)
1,200-1,500
10-40C
1,240-1,510
Alternative fumigant is metam sodium (Vapam^.
b Assumes 1 pound of seed planted per acre.
0 Based on a hybrid cost range of $50-75 for cucurbits and $500-1000 for tomatoes and
eggplants; and a open pollinated cost range of $10-40 for cucurbits, tomatoes, and
eggplants.
Sources: Seals 1996, McKenry 1996, Slaughter 1996, Titts 1996, Emershad 1996, Moling 1996,
VanSickle 1996, Cotton 1996.
References
Ashworth, William. 1991. The Encyclopedia of Environmental Studies. New York, Fact on File Publishers.
Becker 1996 (August). Personal Communication. O.Becker. University of California at Riverside. Riverside,
California.
Cook and Evans 1987. "Resistance and Tolerance." R. Cook and K. Evans. In Principles and Practice of Nematode
Control in Crops. Edited by R.H. Brown and B.R. Kerry. Academic Press.
Cotton 1996 (August). Personal Communication. D. Cotton. 'Seedway, Inc. Elizabeth, PA.
Dunn, 1993. Managing Nematodes in the Home Garden. Robert A. Dunn. Publication of the Florida Cooperative
Extension Service.
Emershad 1996 (August). Personal Communication. Rick Emershad. USDA Plant Breeding Station. Fresno, CA.
Fortnum 1996 (August). Personal Communication. Bruce Fortnum. Dee Dee Research and Education Center.
Blackville, South Carolina.
Gaur and Seshadri 1986. Ecological Control in Evolving Strategies for Nematode Control in 2000 AD. H.S. Gaur
and A.R. Seshadri. Proc. Indian Natn. Sci. Acad. Volume G52, Number 1, pp. 49-65.
-------
Hague and Gowen 1987. "Chemical Control of Nematodes." In Principles and Practice ofNematode Control in
Crops. N.G.M. Hague and S.R. Gowen. Edited by R.H. Brown and B.R. Kerry. Academic Press.
Khan and Khan 1991. "Response of Tomato Cultigens to Meloidogyne javanica and Races of Meloidogyne incognita."
A. A. Khan and M.W. Khan. In Supplement to Journal ofNematology, Volume 23.
Lehman and Cochran 1991. How to Use Resistant Vegetable Cultivars to Control Root-Knot Nematodes in Home
Gardens. P.S. Lehman and C. Cochran. Publication of the Florida Department of Agricultural and Consumer
Services. Division of Plant Industry.
McKenry 1996 (August). Personal Communication. M.V. McKenry. University of California. Kearney Agricultural
Center. Parlier, CA.
McKenry 1987. "Control Strategies in High Volume Crops." M.K. McKenry. hi Principles and Practice of
Nematode Control in Crops. Edited by R.H. Brown and B.R. Kerry. Academic Press.
McKenry and Kretsch 1995. "It is a long road from the finding of a new rootstock to the replacement of a soil
fumigant." M. V. McKenry and J.O. Kretsch. In Proceedings of the 7995 International Conference on Methyl
Bromide Alternatives and Emissions Reductions. San Diego, CA.
McKenry and Roberts 1985. Phytonematology Study Guide. M.V. McKenry and P.A. Roberts. Cooperative
Extension University of California. Division of Agriculture and Natural Resources. Publication 4045.
Moling 1996 (August). Personal Communication. JohnNoling. Florida Extension Service, Citrus Research Center.
Florida.
Potter 1996. Resistance and tolerance of strawberry cultivars to Pratylenchus penetrans in Ontario. John Potter.
Journal of Nematodology. Volume 27, Number 4, pp. 490-528.
Seals 1996 (August). Personal Communication. Joe Seals. W. Atlee Burpee and Company. Warminster, PA.
Slaughter 1996 (August). Personal Communication. John Slaughter. Burchells Nursery. Madera, California.
Thies 1995. "Effectiveness of resistance to the southern root-knot nematode (Meloidogyne incognita) in pepper
(Capsicum annuum)." J.A. Thies, R.L. Fery, and J.D. Mueller, m Proceedings of the 7995 International
Conference on Methyl Bromide Alternatives and Emissions Reductions. San Diego, CA.
Titts 1996 (August). Personal Communication. Margueriette Titts. Geno's. Medera, California.
VanSickle 1996 (August). Personal Communication. John Van Sickle. University of Florida. Gainseville, Florida.
Wehner 1991. "Resistance to Root-Knot Nematodes in Cucumber and Homed Cucumber." Todd C. Wehner, et al. In
Supplement to Journal ofNematology, Vol. 23, 1991.
-------
v>EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1996
Protection Agency
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Chloropicrin Applications for California Strawberries
Preplant soil treatment with chloropicrin (trichloronitromethane), alone, or in combination with other soil
fumigants and pest control measures, can be used by strawberry growers as an alternative methyl bromide.
Currently, there is widespread use of methyl bromide formulations that typically contain 33 percent chloropicrin for
preplant fumigation treatments of strawberry nursery and production fields. These fumigation treatments are
performed prior to planting and typically provide significant season-long control of a broad spectrum of soilborne
pests, including a variety of fungal and nematode pathogens and weeds (USDA 1996).
The strawberry industry in California has
favored the use of methyl bromide formulations that
contain chloropicrin because of the synergistic effects
of these two compounds. Tests and field experience
have verified .these effects and have shown that
chloropicrin offers superior control of fungal pests,
whereas methyl bromide is a better broad spectrum
fumigant with efficacy against a wide range of
pathogens, including weeds and nematodes (Liebman
1994, Wilhelm and Storkan 1990).
Benefits of Chloropicrin
Effectively controls soilborne fungal pathogens.
Its effectiveness is increased when used in
combination with other soil fumigants.
Is commercially available as the sole active
ingredient or in formulations with Telone®.
Recent interest in developing effective
alternatives to the use of methyl bromide as a preplant
fumigant in the California strawberry industry has led to design of experiments and field trials which test the
effectiveness of chloropicrin in both nursery and field settings, alone, and in combination with fumigants such as
Vapam* and Telone*. The results of field studies suggest that the use of chloropicrin will offer strawberry nursery
and fruit producers in California a pest management tool for combating soil diseases caused by soilborne fungal
pathogens (Duniway and Gubler 1996, Duniway et al. 1994, Coffey et al. 1994, Welch and Gubler 1994).
Furthermore, in situations where soil fungi are the principle pests of concern, and other pests such as weeds and
nematodes are controlled through other measures (e.g., alternative fumigants), it is possible that the use of
chloropicrin will allow strawberry producers to effectively control soilborne fungal pathogens thereby promoting
strawberry plant growth and crop yields similar to those achieved with methyl bromide fumigation.
The Importance of Fumigation to Strawberry Production in California
Finding alternative soil pest control measures has been a priority for the California strawberry industry
because of its reliance on methyl bromide/chloropicrin fumigation to achieve superior yields and high quality fruit.
California produces 75 to 80 percent of the nation's strawberries on less than half of the total U.S. strawberry acreage
planted each year (Welch 1989). Average yields in California range from 24 to 40 tonnes per acre, values that are
several times higher than those found in other parts of the country (i.e., Florida, Oregon, and North Carolina), hi
1995, there were 23,600 acres of strawberry production in California yielding 1.19 billion pounds of strawberries
with an average wholesale price of $46.30/100 Ibs. Overall, the 1995 California strawberry crop was valued at $552
million (Hill 1996).
-------
California's high strawberry yield can be attributed to the fact that California has adopted an annual planting
system, developed highly productive strawberry cultivars, and has a cool climate to enhance strawberry production
(USDA 1994). Because plants are grown as annuals, strawberry production in California occurs throughout most of
die year (Welch 1989). Nearly all strawberry acreage in California is fumigated to control weeds, fungi, and
nematodes, and use clear plastic mulch, irrigation, and fertilizers. Approximately 4.5 million pounds of methyl
bromide are used annually in California for pre-plant fumigant of strawberries, representing roughly 35 percent of the
total use of methyl bromide in California, 7 percent of United States use, and 4 percent of world use (DPR 1990-
1992, NAPIAP 1993, UNEP 1992, EPA 1995).
In addition to its widespread use in fruiting fields, methyl bromide is considered to be a critical part of
current produciton practices for strawberry nurseries to ensure the cleanliness of transplanted nursery stocks.
Strawberry runners (transplants) are produced in nurseries and are then shipped to the fruiting fields throughout
coastal and southern California each year where they are transplanted. All California strawberry growers depend on
clean nursery stocks each year because there is a high risk that pathogens can be transplanted from the nurseries to
the fruiting fields. In addition, researchers depend on nursery stock that has been produced using pre-plant
fumigation with methyl bromide/chloropicrin (Larson 1996).
In California, fumigation with methyl bromide/chloropicrin is typically performed by contract applicators.
Fields are covered with a clear plastic during the fumigant application process to hold the gas in the soil and increase
efficacy (Voth et al. 1973). The tarp is removed after at least 24 hours and a clear polyethylene mulch is applied
(usually in November) to warm the soil and promote early plant growth. Plants are then set into the planting beds in
pre-moistened soil. If bed fumigation is used, the fumigation plastic remains in place for the duration of the crop
cycle (USDA 1994).
Advantages of Chloropicrin
Chloropicrin currently appears to offer advantages as a soil fumigant because its use parameters are
relatively familiar to applicators and its efficacy on economically important pests has been well documented. Despite
the proven benefits of Chloropicrin, the long-term effect of soil fumigation with higher dosages Chloropicrin,
community exposure concerns, and requisite dosages are still being evaluated.
Chloropicrin is a restricted use pesticide and is available in formulations with Telone* or as the sole active
ingredient. Chloropicrin is typically injected six to eleven inches into the soil as a liquid 14 days or more before
planting. It is a clear, colorless, nonflammable liquid with a moderate vapor pressure, and it rapidly diffuses through
the soil profile and is toxic to common root destroying fungi. Chloropicrin is not considered to pose a threat to the
ozone layer, it undergoes rapid degradation in sunlight, it is metabolized in soil to form carbon dioxide, and is not
expected to accumulate in plant tissue. In addition, it is not soluble in water and therefore is not expected to pose a
threat to groundwater. Finally, it is not expected to accumulate in animal cells. (USDA 1996).
Research on the efficacy of Chloropicrin for strawberry production has been conducted and is ongoing.
Chloropicrin is best known for its wide spectrum effectiveness in controlling soilbome fungi; however, it has
particular effectiveness in controlling several genera, including Ceratobasidium, Colletotrichum, Cylindrocarpon,
Fusarium, Idriella, Phytophthora, Pyrenochaeta, Pythium, Rhizoctonia, and Verticillium, all of which are known to
cause root rot and/or wilt diseases in strawberries (Wilhelm and Westerlund 1993, Maas 1984). Chloropicrin may
also have some degree of control of root destroying insects, slugs, snails, earwigs, root weevils, grubs and root lesion
types of nematodes (Wilhelm and Westerlund 1993, USDA 1996).
Although some studies have shown that Chloropicrin, when used as the sole active ingredient, is not as
effective as methyl bromide/chloropicrin for fruit production or for the production of certified nursery stock (Shaw
1996, Larson 1996), a number of studies have indicated that strawberries treated with Chloropicrin achieve yields
similar to those attained with methyl bromide. For example, one California study demonstrated that strawberries
planted in soil treated with 20 gallons Chloropicrin per acre resulted in higher yields (6,428 trays/acre) compared to
those grown with methyl bromide/chloropicrin (6,265 trays/acre) (Welch and Gubler 1994). Likewise, a similar
study by Larson and Shaw (1994) found that approximately 100 pounds of Chloropicrin applied produced higher yields
-------
(2,322 trays/acre) compared to that produced wifli methyl bromide/chloropicrin (2,303 trays/acre). The positive
results of these studies support the findings that chloropicrin is an excellent fumigant for the control of soilborne
fungi.
However, because the use of chloropicrin is not as effective as other compounds (e.g., Telone®) in
controlling weeds and nematodes, research is now being conducted to further evaluate the effectiveness of
chloropicrin when it is used in conjunction with other chemicals (Coffey, et al. 1994, Duniway and Gubler 1996).
Results from these studies suggest that by combining chloropicrin treatments with other treatments, especially
Telone*, control of many of the nematode and weed pests currently controlled with methyl bromide/chloropicrin
fumigation treatments may be possible, hi addition, the development of fumigant formulations that contain higher
levels of chloropicrin may provide excellent pathogen control without requiring alterations to existing cultivation
methods (USDA 1996).
Costs
Strawberries are among the most expensive crops to grow, with annual production costs as high as $24,600
per acre (attributed primarily to materials and harvesting costs) (Gliessman et al. 1990). Although profits and losses
vary considerably depending on the size of the crop and fluctuations in market price, profits of $3,500 to $5,000 per
acre or more have been reported (Gliessman et al. 1990, Webb 1994, Cochran 1994).
Although costs resulting from the need to perform additional pest control measures may be incurred
(e.g., application of Telone*), the actual costs associated with applying chloropicrin (e.g., injection and tarping) will
be similar to those for methyl bromide (Wilhelm 1995). However, one of the principle differences in the cost of
chloropicrin versus methyl bromide/chloropicrin use in the California strawberry industry will be the material cost of
the chemical (i.e., $675/acre for chloropicrin compared to $615/acre for methyl bromide/chloropicrin (67:33)). A
material cost comparison is provided in Table 1 below:
Table 1. Raw Materials Cost Comparison
Cbloropieiin "
Application Rate
100 to 300 Ibs.
a.i./acre
350 to 450 Ibs.
a.i./acre
300 to 375 Ibs.
a.L/acre
Cost per Pound
$2.25/lb.
$1.59/lb.
$1.64/lb.
Total Material Cost
$225 to $675/acre
$556 to $715/acre
$492 to $615/acre
Sources: Wilhelm 1995, Asgrow 1995, Coffey, et al. 1994, Duniway et al. 1994, Fowler 1996.
-------
References
Asgrow. 1995 (February 1). Personal Communication. Asgrow. Price Quote for Methyl Bromide.
Coffey, et al. 1994. Evaluation of alternative soil fumigation methods for use in strawberry production in southern
California. M. Coffey, A.O. Paulus, I. Schmitz, P. Rich, H. Krueger, M. Meyer-Podolsky, H. Forster, M. Vilchez,
and F. Westerlund. In 1994 Annual International Research Conference on Methyl Bromide Alternatives and
Emission Reductions: Conference Proceedings. Number 1. Kissimmee, Florida.
Cochran. 1994. Personal Communication. J. Cochran. Swanton Berry Farms. Davenport, California.
DPR. 1990-1992. Annual Pesticide Use Reports. Department of Pesticide Regulation, State of California
Environmental Protection Agency. Sacramento, California.
Duniway et al. 1994 (November 13-16). Evaluation of strawberry growth, fruit yield, and soil microorganisms in
non-treated soil and in soil fumigated with methyl bromide/chloropicrin, Telone n/chloropicrin, chloropicrin, or
Vapam in a California strawberry production system. J. Duniway, W. Gubler and N. Filajdic. In 1994 Annual
International Research Conference on Methyl Bromide Alternatives and Emissions Reductions: Conference
Proceedings. Number 16. Kissimmee, Florida.
Duniway and Gubler. 1996. Evaluation of some chemical and cultural alternatives to methyl bromide fumigation of
soil in a California strawberry production system. J. Duniway and D. Gubler. hi 1996 Annual International
Research Conference on Methyl Bromide Alternatives and Emissions Reductions: Conference Proceedings. Number
37. Orlando, Florida.
EPA. 1995. Methyl bromide consumption estimates. U.S. Environmental Protection Agency, Stratospheric
Protection Division, Washington, DC. August 7, 1995.
Fowler. 1996. Price quote for Telone® and chloropicrin. Kirk Fowler, Tri-Cal, HoUister, California, December 10,
1996.
Gliessman et al. 1990. Strawberry production systems during conversion to organic farming. S.R. Gliessman, S.L.
Swezey, J. Allison, J. Cochran, J. Farrell, R. Kluson, F. Rosado-May, and M. Werner. Calif. Agric. Volume 44,
pp. 4-7.
Hill. 1996. Personal Communication. Howard Hill. National Agricultural Statistics, United States Department of
Agriculture.
Larson. 1996 (July, December). Personal Communication. Kirk Larson. University of California at Davis. Davis,
California.
Larson and Shaw. 1994. Evaluation of Eight Preplant Soil Treatments for Strawberry Production in Southern
California. Larson, K.D. and D.V. Shaw. In 1994 Annual International Research Conference on Methyl Bromide
Alternatives and Emissions Reductions: Conference Proceedings. Number 24. Kissimmee, Florida.
Liebman. 1994 (July). Alternatives to methyl bromide in California strawberry production. Jamie Liebman. In The
IPM Practitioner. Volume XVI, Number 7, pp. 1-12.
Maas et. al. 1984. Compendium of Strawberry Diseases. J. L. Maas, ed., The American Phytopathological
Society, St. Paul, Minnesota.
NAPIAP. 1993 (April). National Agricultural Pesticide Impact Assessment Program. Biologic and Economic
Assessment of Methyl Bromide. United States Department of Agriculture.
-------
Shaw. 1996. Analysis of chloropicrin efficacy for strawberry production. Unpublished study, Dr. D. Shaw,
University of California, Davis. December 5, 1996.
UNEP. 1992. Methyl Bromide: Its Atmospheric Science, Technology, and Economics. UN Ozone Secretariat,
United Nations Environmental Programme. Nairobi, Kenya.
USDA. 1996. Methyl bromide alternatives. U.S. Department of Agriculture, Washington, DC, Newsletter, July
1996.
USDA. 1994. The U.S. strawberry industry. Economic Research Service, United States Department of
Agriculture. Statistical Bulletin Number 914.
Webb. 1994. Personal Communication. R. Webb. Driscoll Strawberry Research. Watsonville, California.
Welch. 1989. Strawberry production in California. N.C. Welch. University of California Cooperative Extension.
Leaflet #2959, p. 15.
Welch and Gubler. 1994 (November 13-16). Soil fumigation experiment in strawberries in the central coast district
of California. Norman Welch and Doug Gubler. hi 1994 Annual International Research Conference on Methyl
Bromide Alternatives and Emissions Reductions: Conference Proceedings. Number 17. Kissimmee, Florida.
Wilhelm and Storkan. 1990. Large scale soil fumigation growth response. S. Wilhelm and R.C. Storkan.
Phytopathology. Volume 49, pp. 530-531.
Wilhelm and Westerlund. 1993. -Chloropicrin - Soil Fumigant. Stephen Wilhelm, University of California and
Frank Westerlund, California Strawberry Commission, California.
Wilhelm. 1995 (February 1). Personal communication. John Wilhelm, Niklor Chemicals.
Voth et al. 1973. Effect of tarp thickness and dosage on response of California strawberries to fumigation. V. Voth,
D.E. Munnecke, A.O. Paulus, MJ. Kolbezen, and R.S. Bringhurst. Calif. Agric. Volume 27, Number 12, p. 14.
-------
-------
EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1336
Protection Agency
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Organic Strawberry Production As An Alternative to Methyl Bromide
Organic strawberry production is an effective integrated approach that offers an alternative to methyl bromide
use for California strawberries. Organic producers do not use methyl bromide or any other synthetic pesticide or
fertilizer in the production of certified organic strawberries (MBRTF 1995). Instead they use organically acceptable
production methods to control or suppress weeds, plant pathogens, and nematodes including the use of plastic mulches
coupled with supplemental hand weeding to suppress weeds, release of mass-reared beneficial insects, soil solarization,
good sanitation practices, resistant cultivars, biological control fungi and/or organic matter, hot water treatments, crop
rotation, various cultural controls, and irrigation management practices (Liebman 1994, University of California 1993,
Liebhardt et al. 1989). These techniques are part of an overall integrated pest management (IPM) program.
There are several advantages to converting conventional, high-input strawberry production systems to organic
systems, including elimination of synthetic fertilizers and pesticides and the building of healthy soil. Recent
improvements in organic strawberry production have resulted in yields as high as 89 percent of that obtained from
conventional strawberry production. Furthermore, organically grown strawberries can be sold at a higher price than
conventional strawberries, thus offsetting any
yield reductions (Cochran 1995). While only
a small percentage of the California
strawberry crop is produced organically,
price premiums of as much as 50 to 100
percent for certified organic strawberries
provide a considerable incentive for growers
to consider organic production techniques in
the future (Gliessman et al. 1994). Organic
strawberry production also eliminates
environmental stress caused by pesticide use,
thus increasing soil biotic diversity and
beneficial organisms (i.e., a complex of
natural predators and parasites) (Liebman
1994, Baker 1996).
Benefits of Organic Strawberry Production
Allows for elimination of synthetic fertilizer and pesticide
inputs
Produces yields as high as 89 percent of that
obtained from conventional strawberry production
Increases price premiums by 50 to 100 percent over that
for conventional production practices.
Reduces environmental stresses and permits an increase
in biotic diversity and beneficial organisms
Reduces the need for methyl bromide and other synthetic
pesticides and fertilizers
Despite the advantages of organic production as an alternative to methyl bromide, it is unlikely that all
strawberry farms will switch to organic production. If all large growers did shift to organic production practices, the
price differential between conventional vs. organic strawberries would decrease along with some of the price incentives
to convert to organic production practices (Baker 1996, Cochran 1996). Instead, without methyl bromide, most
conventional (non-organic) California strawberry producers probably would be able to use a variety of other pesticides
to help improve yields over those obtained under organic systems alone. For example, the use of chloropicrin, and other
synthetic chemical treatments applied in addition to the "organic" approaches discussed here can further improve yields
(Gliessman etal. 1996).
California Fresh Market Strawberries
California strawberry growers produce 75 percent of the fresh market strawberries and 80 percent of the
processed strawberries in the United States (Welch 1989) on only about 19,250 acres of land (mainly in Central Coastal
counties in California) (Gliessman et al. 1996, Larson and Shaw 1994). Strawberry production in California typically
-------
occurs all year long (Welch 1989) with yields steadily increasing over time for the last four decades, making it one of the
most valuable and stable crops in the state (Wilhelm and Paulus 1980). However, strawberries are also one of the most
expensive/labor intensive crops to grow (Gliessman et al. 1990 and 1996, Webb 1994, and Cochran 1995).
Although strawberries are a perennial crop, commercial growers in California treat them as annuals, planting new
transplants from nurseries in the Sierra foothills each year (Liebman 1994). Californian farmers routinely obtain
superior yields over producers in other states (i.e., Oregon, Florida, Louisiana, and North Carolina). For example,
California strawberry production yields average 24 tons per acre, with some growers obtaining between 35 to 40 tons
per acre, several times higher than that achieved in other states (Wilhelm and Paulus 1980).
The loss of methyl bromide will also have an impact on strawberry nurseries. Because California strawberries
are grown as annuals, nurseries must grow transplants for the entire crop each year. In the past, methyl bromide has
been the key to producing clean planting stocks. However, without methyl bromide, careful monitoring for pests,
vigilant sanitation efforts, and the use of other soil disinfestation techniques (i.e., steam and biocontrol inoculants) will
be needed in the future, hi addition, it may be necessary to grow plants in bags of sterilized peat or rock wool, similar to
that used for strawberry production in The Netherlands and for other nursery crops in the U.S. (Liebman 1994).
Overview of Methyl Bromide Use in Conventional California Strawberry Production
Methyl bromide has been used extensively as a preplant fumigant in California strawberry production and is
one of the keys to the stability and economic viability of the California strawberry market (Wilhelm and Paulus 1980).
In 1992, about 85 percent of the state's crop was planted on land that was fumigated with a total of 4.5 million pounds of
methyl bromide (USDA 1993), representing approximately 25 percent of all methyl bromide applied in California and
about 10 percent of the total annual domestic use of methyl bromide (Liebman 1994). The only strawberry land that is
not fumigated are those plots certified for organic production (less than 100 acres in the state) or crops left in the ground
forasecond year (10-20 percent of California's strawberry acreage) (Westerlund 1994,Liebman 1994).
In conventional California strawberry production, growers fumigate land to be planted to strawberries with a
mixture of methyl bromide and chloropicrin (2:1 ratio) for the control of most plant pathogens, nematodes, and weeds
(Braun and Supkoff 1994, Welch et al. 1985). Because of the need for specialized application equipment and concerns
for worker safety, methyl bromide can only be applied by licensed applicators (University of California 1993).
Application rates range from 300 to 400 pounds per acre with associated treatment costs of approximately $1,200 to
$1,400 per acre (Liebman 1994). The frequency of fumigation is determined by the rotation sequence practiced by the
grower. Some growers, especially in Southern California, plant strawberries each year and fumigate before each crop is
planted. On the Central Coast near Watsonville, growers often rotate crops (i.e., bellbean, barley, lettuce, broccoli,
cauliflower, or celery) and fumigate alternating years (Westerlund 1994 & 1996, Liebman 1994).
Organic Production Techniques as a Replacement for Methyl Bromide
Twenty-two of the 600 strawberry farms in California are certified as organic according to The California
Certified Organic Farmers Directory. Unlike conventional strawberry farmers, organic farmers use a rotation of 1 to 2
berry crops every 4 to 5 years and do not use methyl bromide or any other synthetic pesticides or fertilizers (Gliessman
et al. 1990, Cochran 1995, Webb 1994). An example of successful organic strawberry production is Swanton Berry
Farms in the central coastal area of California, which has profitably grown strawberries without synthetic inputs
(including methyl bromide) since 1986 (Cochran 1995). Weeds, soilborne pests, and diseases are controlled or
suppressed using a combination of organically acceptable methods, including crop rotation and cover crops, plastic
mulch, compost, cultural controls, and careful management of naturally occurring beneficial predators with
supplementary releases of mass-reared beneficials when needed (Gliessman etal. 1996, Cochran 1995).
Costs Associated with Organic Strawberry Production
Limited research has been conducted on organic strawberry production costs and techniques and the
conversion from conventional strawberry production to organic production in California (Gliessman et al., 1994,
Liebman 1994). hi one three-year university sponsored, on-farm research trial conducted at Swanton Berry Farms,
University of California researchers initially achieved strawberry yields that were 68 percent of strawberries produced
with conventional chemicals (Gliessman.et al. 1994). While yields were lower for organically produced strawberries,
-------
they steadily improved over the study period from 2,068 trays per acre in the first year, to 2,388 trays per acre (79
percent) in the third year. Specifically, organic yields relative to those of conventional strawberries were 39 percent
lower in the first year, 30 percent in the second year, and 28 percent in the third year (Gliessman et al. 1996). Similar
studies on conversion to organic production of strawberries and other crops support these findings — i.e. that yields
increase over time (Sances and Ingham 1995, Liebhardt et al. 1989). More recently, Swanton Berry Farm's has been
able to achieve yields as high as 3,100 trays per acre, a 13 percent improvement over yields attained in the previous 3
year study and 89 percent of the yield using conventional techniques (Cochran 1995). However, when comparing these
yields to those of conventional strawberry growers, it must be noted that the variety of strawberries planted at Swanton
Berry Farms are grown primarily for taste, and are not considered to be a high yielding variety, hi addition, the area
where the farm is located is not conducive for achieving the highest yields possible with the variety currently grown.
Slightly lower yields are offset by higher prices paid for certified organic strawberries (Gliessman et al. 1990).
For example, production costs range from $18,919 to $23,668 and $20,480 to $24,437 per acre for organic vs.
conventional strawberry production practices (See Table 1). hi the first two years, input costs associated with
pesticides, fertilizers, and fuel were higher in conventional strawberry production; however, organic production
practices require more hours of tractor work for mechanical weeding and longer picking times, resulting in higher labor
costs for organic strawberry production (Gliessman et al. 1996). Price premiums of up to 50 percent or more have been
attained by Swanton Berry Farms. As a result, profits range from $3,039 to $9,738 for organic strawberries compared
to $2,303 to $6,087 per acre for conventional strawberries (Gliessman et al. 1996). As demonstrated by these values,
organic strawberry production can be profitable, hi fact, compared with traditional, chemical-intensive production
practices, results indicate that organic strawberries were 83 percent and 60 percent more profitable in the second and
third years, respectively (Liebman 1994).
Table 1. Comparative Strawberry Production Costs and Returns (S/acre)
Organic
Tear 1
Year 2
Year3
Conventional
Year 1
Year 2
Year 3
Cultural
labor
Materials
-------
References
Baker 1996 (September). Personal Communication. Brian Baker. California Certified Organic Growers. Santa Cruz,
California
Braun and Supkoff. 1994. Options to methyl bromide for the control of soil-borne diseases and pests in California with
reference to the Netherlands. A. Braun and D. Supkoff. Pest Management Analysis and Planning Program, State of
California. PM 94-02.
Cochran 1996 (September). Personal Communication. J. Cochran. Swanton Berry Farms. Davenport, California.
Cochran 1995 (February). Personal Communication. J. Cochran. Swanton Berry Farms. Davenport, California.
Gliessman et al. 1996. Conversion to organic strawberry management changes ecological processes. S.R. Gliessman,
M.R. Werner, S.L. Swezey, E. Caswell, J. Cochran, F. Rosado-May. California Agriculture. Volume 50, Number 1, pp.
24-31.
Gliessman et al. 1994. Conversion to an organic strawberry production system in coastal central California: a
comparative study. S.R. Gliessman, M.R. Werner, S.L. Swezey, E. Caswell, J. Cochran, F. Rosado-May. Agroecology
Program, University of California. Santa Cruz, California
Gliessman et al. 1990 (July/August). Strawberry production systems during conversion to organic management. S.R.
Gliessman, S.L. Swezey, J. Allison, J. Cochran, J. Farrell, R. Kluson, F. Rosado-May, and M. Werner. California
Agriculture. Volume 44, Number 4, pp. 4-7.
Larson and Shaw 1994 (November 13-16). Evaluation of eight preplant soil treatments for strawberry production in
southern California. In 1994 Annual International Research Conference on Methyl Bromide Alternatives and
Emissions Reductions: Conference Proceedings. Number 24. Kissimmee, Florida.
Liebman 1994 (July). Alternatives to methyl bromide in California strawberry production. J. Liebman.
The IMP Practitioner. Volume 16, Number 7.
Liebhardt et al. 1989. Crop production during conversion from conventional to low-input methods.
W. Liebhardt et al. Agronomy Journal. Volume 81, pp. 150-159.
MBRTF, 1995 (September). Alternatives to Methyl Bromide: Research Needs for California. Report of the Methyl
Bromide Research Task Force To The Department of Pesticide Regulation and The California Department of Food and
Agriculture.
Stance and Ingham 1995 (November 6-8). Suitability of organic compost and broccoli mulch soil treatments for
commercial strawberry production on the California central coast. In 1995 Annual International Research Conference
on Methyl Bromide Alternatives and Emissions Reductions: Conference Proceedings. Number 19. San Diego,
California.
University of California. 1993. UCIPM pest management guidelines. Division of Agriculture and Natural Resources,
University of California. Publication #3339.
USD A. 1993 (June). Agricultural chemical usage, vegetables 1992 summary. National Agricultural Statistics Service,
United States Department of Agriculture.
Webb. 1994. Personal Communication. R. Webb. Driscoll Strawberry Research. WatsonviUe, California.
Welch. 1989. Strawberry production in California. N.C.Welch. University of California Cooperative Extension.
Leaflet #2959, p. 15.
Welch et al. 1985. Strawberry production and costs in the central coast of California. N. Welch, et al. Agricultural
Extension, University of California.
-------
Westerlund. 1994 & 1996. Personal Communication. Frank Westerlund. California Strawberry Commission.
California.
Wilhelm and Paulus. 1980. How soil fumigation benefits the California strawberry industry. S. Wilhelm and A.O.
Paulus. Plant Dis. Volume 64, pp. 264-270.
-------
-------
&EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1336
Protection Agency
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Serialization for Controlling Soilborne Pests and Pathogens
in Field Crop Cultivation
Serialization is a method in which clear plastic is laid on the soil surface to trap solar radiation and heat the
soil. Solarization as a preplant soil treatment to control soilborne pathogens and pests can be a viable alternative to
methyl bromide for shallow-rooted, short-season crops (Katan and DeVay 1991, Stapleton 1996). Solarization is a
hydrothermal process that can be used in moist soils covered with clear plastic tarps and exposed to direct sunlight in
tropical climates or during warm summer months in more temperate regions. Solarization traps solar radiation, and
thereby heat, in the soil in order to raise temperatures sufficiently to suppress or eliminate soil-bome pests and
pathogens (Katan 1981 and 1991). It can be effective against a broad spectrum of soil diseases, fungi, weeds,
nematodes, insect pests and most soilborne bacteria. Solarization also causes complex changes in the biological,
physical, and chemical properties of the soil that improve plant development, growth, quality, and yield for up to several
years (Stapleton 1994, Katan 1981 and 1991, DeVay et al. 1990). hi areas with a suitable climate, Solarization can be
used alone, or in combination with lethal or sublethal fumigation or biological control, to provide an effective substitute
to methyl bromide (Hartz et al. 1993).
hi addition to disinfecting the soil while
reducing or eliminating the need for fumigants,
Solarization leaves no toxic residues, increases the levels
of available mineral nutrients in soils by breaking down
soluble organic matter and making it more bioavailable,
changes the soil microflora to favor beneficial organisms,
conserves water, and can serve as a mulch when
maintained as a row cover during the growing season
(Stapleton 1994, Katan and DeVay 1991). However,
Solarization appears only to be effective hi warm
climates and requires that cultivated land be left fallow
for short periods of tune (Katan and DeVay 1991).
Research
Benefits of Solarization
Can be combined with other pest management
practices
Can provide effective pathogen control for several
years
Stimulates increased plant growth response,
resulting in higher crop quality and yield
Increases levels of mineral nutrients in soils
Promotes biological control
Conserves water
Solarization alone, or in combination with other pest control technologies, could be adopted as a preplant soil
pest control measure for a variety of different pathogens and pests in a wide range of climates and different cropping
systems. Since its inception in 1976, soil Solarization has been tested and modified under local conditions hi more than
50 countries, including the United States (Florida, California, North Carolina and other states), Israel, Greece, Morocco,
and Japan, for the control of nematodes, weeds, and disease organisms affecting a variety of vegetable and fruit crops
(Hartz et al. 1993, Katan 1984 and 1981, Ristaino et al. 1996 and 1991, Stapleton 1994, Wu 1996). Studies have
shown that 1) Solarization reduces or eliminates pathogens and pests prior to planting, 2) crop yields can be significantly
increased, and 3) the effects of Solarization can extend through several growing seasons (Afek et al. 1991). Solarization
has already proven to be an effective pest control tool for tomato, pepper, and eggplant production in the northern part of
Florida and North Carolina, strawberry and lettuce production in California (Gamliel and Stapleton 1993, Hartz et al.
1993, Ristaino et al. 1991), tree nursery production in the southeastern U.S., and orchard crops in California (Chellemi
1994, DeVay et al. 1990, Littke 1994a, Littlce 1994b, Stapleton 1994). Solarization also has proven effective in
controlling pests (pathogens) for a variety of other crops including pistachios, almonds, carrots, garlic, peanuts, potatoes,
watermelon, onions, artichokes, and beans (Katan and DeVay 1991). It must be noted that the effectiveness of this pest
control tool is directly linked to climate - that is, the amount of sunlight received during the Solarization process, hi
addition, as with other pest control tools, the effectiveness of Solarization is related to how well it is applied and the
experience of the persons involved in the process.
-------
Because of its passive nature, solarization alone is limited to growing areas in primarily hot, generally cloudless
climates. However, it has also shown considerable promise for vegetable production in more humid areas, such as the
southeastern United States where average soil temperatures at 5 cm depth are 50°C in solarized plots and 36°C in bare
ground. Variations of the principle have also been used in other locations. For example, in the Rio Grade Valley in
Texas and in Northern Florida, transparent film used to solarize fields during the hot summer off-season is then painted
white and left in place to serve as a mulch for the fall melon and tomato crops. In the Jordan Valley in Israel, black
plastic has been used to solarize soil during the extremely hot summer months, and is then left in place to serve as a
mulch for the fall vegetable crop. These modifications represent excellent adaptations of the technique for maximizing
cost effectiveness (Stapleton 1996). Additionally, while not currently commercially feasible in most cases, the use of
recycled/old plastics has been shown to be more effective at heating the soils than new plastics because the photometric
properties of transparent polyethylene sheets change significantly during the aging process (Katan and DeVay 1991).
Solarization Techniques
Generally, a layer of clear plastic film is applied to the soil prior to planting and is left in place for 4 to 6
weeks during the hot season in the appropriate climatic region. Optimal use, however, may require a longer period of
time and adjustments in scheduling for other production practices. However, this time period may be reduced by
combining solarization with chemical or non-chemical pesticides. Proper soil preparation also is essential to provide a
smooth, even surface for the tarp and allow water to penetrate evenly and deeply into the soils (Stapleton 1996). To
maintain proper soil moisture, irrigation using sprinklers is typically performed 1 to 4 days prior to applying the plastic
tarp. Alternatively, drip irrigation lines can be installed underneath the tarp and utilized as necessary (Katan 1981).
Plastics may be applied either in strips (usually 2 feet wide) over the planting beds or as continuous sheeting glued, heat
fused, or held in place by soil. Because pathogens that survive heat treatment within or at the periphery of treated soils
tend to multiply (a phenomenon known as the "edge or boarder effect"), continuous sheeting is thought to be more
effective than strip applications, although it is more expensive (Katan and DeVay 1991, CEUC, 1984). However, soil
temperatures under bed solarization in the southeastern United States are higher than temperatures achieved under full-
field solarization. In addition, the border-effect associated with the lack of pest suppression along the edges of full-field
solarization is eliminated by bed solarization (Chellemi, 1996). Currently the most common film types used for
solarization are UV-resistant clear polyethylene or polyvinyl chloride film (Katan and DeVay 1991). Double layers of
plastic, which simulate solarization of soil under glasshouse conditions, result in even greater temperature increases in
soils (i.e., 3 to 10°C higher that achieved under a single layer of plastic) ( DeVay et al. 1990).
After solarization, the plastic is either removed or left in place to serve as mulch during the growing season
(Katan and DeVay 1991). The physical, biological, and chemical changes that occur during solarization may persist for
up to 2 years (Katan and DeVay 1991, DeVay et al. 1990). Because soil temperatures are the highest within the
uppermost layers, cultivation after solarization should be kept to a minimum to avoid reinfestation from pests deep in the
soils. To achieve lethal soil temperatures at greater depths, solarization must be maintained at higher temperatures for
an extended period of time (two months or longer) (Katan 1987). However, the use of double layered plastic may
reduce time necessary for this procedure to control pests.
Solarization causes physical, chemical, and biological changes in the soil by raising soil temperatures from 2-
15°C above the temperatures of untreated soil. For example, temperatures achieved with solarization in Israel during
July and August, at levels between 5 and 20 cm below the soil surface were 45-55 °C and 39-45°C, respectively, hi
California, at a depth of 5 cm, the temperature of tarped soil was recorded at 60°C (Katan 1981). In Florida, at depths
of 5,15, and 25 cm, temperatures of 49.5,46.0, and 41.5, respectively, were recorded in solarized soil (Chellemi 1994)
The success of soil solarization is based on the fact that most plant pathogens and pests are mesophilic or unable to
survive for long periods at temperatures above 37°C. The heat sensitivity of these organisms is related to an upper limit
in the fluidity of cell membranes, which lose their ability to function at high temperatures. Other causes of death of
organisms at high temperatures involve the sustained inactivation of enzyme systems, especially respiratory enzymes
(DeVay et al. 1990). Pathogens may be killed either directly by the heat or are weakened by sublethal heat to the extent
that they are unable to damage crops (DeVay 1996).
Solarization also promotes increases in plant growth and development and crop quality and yield by increasing
the availability of plant nutrients and the relative populations of beneficial organisms such as rhizosphere bacteria
(Bacillus spp.) and pseudomones species (Ristaino et al. 1991). Heating causes the release of soluble mineral nutrients
from soil organic matter and heat killed soil biota and induces the upward movement of mineral nutrients in the soil
profile. Reductions in populations of soil borne pathogens also constitute the basis for biological control of plant
-------
pathogens and in some cases the development of disease suppressive soils (Katan and DeVay 1991, Stapleton 1996,
Ristainoetal. 1991).
The effectiveness of solarization and the heat dosages achieved for disinfesting soil depend on soil moisture and
texture; air temperature (maxima, minima, and duration); season; length of day; intensity of sunlight; wind speed and
duration; and the type, color, and thickness of the plastic (DeVayetal. 1990, Katan and DeVay 1991). The greater the
temperature, the less time is needed to reach a lethal heat dosage. For example, at soil temperatures of 37°C (the lower
threshold temperature for lethal and sublethal damage for many mesophilic fungi) exposure may require from 2 to 4
weeks, however at 47 ° C, 1 to 6 hours of exposure is a lethal dose (Katan and DeVay 1991). Because solarization is a
hydrothermal process, its success also depends on moisture for maximum heat transfer to soilbome organisms (Chellemi
1995). However, recently a soil temperature model that predicts temperature under plastic mulch based on above
ground meteorological data has been developed (Wu et al. 1996)
Reducing Chemical Usage and Costs
Solarization can be a cost-effective technique for controlling soil-borne pests of fruits, vegetables, nursery, and
orchard crops, making it a viable alternative to methyl bromide in many warm climates. This is supported by an
economic analysis of 30 single-crop, single-season experiments which suggested that solarization was effective and
profitable for numerous shallow-rooted, short season crops (Katan and DeVay 1991). Furthermore, additional benefits
of solarization, such as an increased growth response and its long-term effects, strengthen its economic profitability
(Katan and DeVay 1991, Stapleton 1994). In addition, solarization can be combined with other chemical, physical, and
biological methods (e.g., fertilizers, soil amendments, integrated pest management strategies, limited pesticide use, and
biological control agents) for enhanced management of soil and root pests and diseases (DeVay 1996, Katan and DeVay
1991). Cost estimates for solarization compared to methyl bromide fumigation are provided in the Table 1 below. As
shown, reduced chemical usage and cost savings can be achieved by using solarization for controlling soil-borne pests.
It should be noted however that with strip and bed solarization, costs can be reduced as the application techniques are
virtually identical to the standard polyethylene mulch culture without the additional labor costs listed here for
solarization (Chellemi, 1996).
Table 1. The Comparative Costs of Solarization and Methyl Bromide Fumigation
Cost Factor
Tarp
Labor
Other
Total
Treatment*!: Solarization
($/aer«)
175-180
100-160
25-100
(post-treatment white paint or tarp removal)
300-440
Treatment*^ MetaylBroatide
($/at**>
225-300
50-80
200-350
(fumigant costs)
475-730 (broadcast up to $1,500)
Source: Chellemi 1995, DeVay 1996, Olson 1996, Hartz 1996, Katan and DeVay 1991.
References
Afek et al. 1991. "Interaction among mycorrhizzae, soil solarization, metalaxyl, and plants in the field." U. Afek, J.A.
Menge, and E.L. V Johnson. Plant Disease. The American Phytopathological Society. Volume 75, No. 7, pp. 665-672.
CEUC 1984. Soil solarization: a nonchemical method for controlling diseases and pests. Cooperative Extension
University of California. Division of Agriculture and Natural Resources. Leaflet #21377
Chellemi, D.O., 1996 (November). Personal Communication. Dr. D. Chellemi. University of Florida. Gainesville, FL
Chellemi, D.O., 1995 (April). Personal Communication. Dr. D. Chellemi. University of Florida. Gainesville, FL
-------
Chellemi, D.O., Olson, S.M., and Mitchell, D.J. 1994. Effects of soil solarization and fumigation on survival of
soilbome pathogens of tomato in northern Florida. Plant Dis. 78:1167-1172.
DeVay 1996 (August). Personal Communication. IE. DeVay. Professor, Department of Plant Pathology. University
of California. Davis, California.
DeVay et al. 1990. Soil Solarization. IE. DeVay, J.J. Stapleton, and C.L. Elmore. Food and Agricultural
Organization, United Nations. FAO Report #109. Rome, Italy.
Gamliel and Stapleton 1993. "Effect of chicken compost or ammonium phosphate and solarization on pathogen control,
rhizosphere microorganisms, and lettuce growth," A. Gamliel and J.J. Stapleton. Plant Disease. The American
Phytopathological Society. Volume 77, No. 9, pp. 886-891.
Hartz 1996 (August). Personal Communication. T. Hartz. Professor, Department of Plant Pathology. University of
California. Davis, California.
Hartz et al. 1993. "Solarization is an effective soil disinfestation technique for strawberry production." T. Hartz, I
DeVay and C. Elmore. HortScience. Volume 28, No. 2, pp. 104-106.
Katanl987. Soil Solarization. IKatan. hi: Innovative Approaches to Plant Disease Control. John Wiley & Sons, Inc.
pp. 77-105.
Katan 1984. "Soil solarization," presented at Second International Symposium on Soil Disinfestation. I Katan.
Leuven, Belgium. Convener C. Van Assche, Commission for Plant Protection.
Katan 1981. "Solar heating (solarization) of soil for control of soilborne pests." IKatan. Annual Review of
Phytopathology. Volume 19, pp. 211-36.
Katan and DeVay 1991. Soil Solarization. I Katan and IE. DeVay. CRC Press Inc. Boca Raton, Ann Arbor, Boston,
London.
Littke 1994a. "Methyl bromide loss: meeting resource management goals through sustainable forest seedling production
using alternative seedling production." Dr. W. Littke. In Proceedings of the 1994 International Conference on Methyl
Bromide Alternatives and Emissions Reductions. Kissimmee, FL.
Littke 1994b (December). Personal communication. Dr. W. Littke, Weyerhaeuser Corporation.
Olson 1996 (August). Personal Communication. Dr. S. Olson. University of Florida. Gainesville, FL.
Ristaino, IB., K.B. Perry and R.D. Lumsden. 1996. Soil solarization and Gliocladium virens reduce the incidence of
souther blight (Sclerotium rolfsii) in bell pepper in the field. Biocontrol Science and Technology 6/4: 583-593.
Ristaino, IB., K.B. Perry and R.D. Lumsden. 1991. Effect of soil solarization and Gliocladium virens on Sclerotia of
Sclerotium rolfsii, soil microbiota, and the incidence of southern blight in tomato. Phytopathology 81:1117-1124.
Stapleton 1996. "Fumigation and solarization practice in plasticulture systems." II Stapleton. HortTechnology.
Volume 6, No. 3, pp. 189-192.
Stapleton 1994. "Solarization as a framework for alternative soil disinfestation strategies in the interior valleys of
California." II Stapleton, hi Proceedings of the 1994 Annual International Research Conference on Methyl Bromide
Alternatives and Emissions Reductions. Kissimmee, FL.
Wu, Y. B.P. Perry and IB. Ristaino. 1996. Estimating temperature of mulched and bare soil form meteorological data.
Agricultural and Forest Meteorology 81 -.299-323.
-------
vvEPA
United States
Environmental
Off ice of Air and Radiation
(6205-J)
December 1996
Protection Agency
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Soil Serialization as an Alternative to Methyl
Bromide In California Orchards
Solarization as a pre- or post-plant soil treatment to control soilbome pathogens and pests is a viable
alternative to methyl bromide in orchard crops such as peaches, plums, nectarines, apricots, walnuts, pistachios,
almonds, apples, and cherries. Currently, methyl bromide is used to control soilborne bacteria and diseases, weeds,
nematodes, and fungi in these crops (DeVay 1995, Stapleton 1995, Pullman et al. 1984). As early as 1981, soil
solarization was successfully used in California to control Verticillium wilt in pistachio tree groves (Ashworth and
Gaona 1982). Since then, extensive soil solarization research has been conducted in orchards and the treatment is being
appraised by many large orchard growers (McKenry 1996). hi 1992, the top five California orchard uses of methyl
bromide (e.g., almonds, nectarines, plums, peaches and walnuts) utilized over 2.5 million pounds of methyl bromide
(State of California 1992).
Solarization is a hydrothermal process that can occur in moist soils covered with plastic tarps and exposed to
direct sunlight in tropical climates or during warm summer months in more temperate regions. Solarization traps solar
radiation, and thereby heat, in the soil and
raises temperatures sufficiently to suppress
or eliminate soil-borne pests and pathogens
(Katan 1981, Katan and DeVay 1991).
Solarization also causes complex changes in
the biological, physical, and chemical
properties of the soil that improve plant
development, growth, quality, and yield for
several years (Stapleton 1994, Katan and
DeVay 1991, DeVay etal. 1990, Katan
1981). In areas with a suitable climate,
solarization can be used alone, or in
combination with lethal or sublethal
fumigation or biological control, to provide
an effective substitute to methyl bromide
(Hartzetal. 1993).
S
s
Benefits of Soil Solarization In Orchards
Can be combined with other pest management practices
Can provide effective pathogen control for several years
Leaves no toxic residues
Conserves water
Increases levels of mineral nutrients in soils
Stimulates increased plant growth response
Promotes biological control
Serves as a mulch when maintained as a row cover
throughout the growing season
In addition to disinfesting the soil while reducing or eliminating the need for fumigants, solarization leaves no
toxic residues and can contribute to water conservation. Furthermore, solarization increases the levels of available
mineral nutrients in soils by breaking down soluble organic matter and increasing bioavailablity. hi doing so,
solarization stimulates an increased growth response in many orchard trees and changes the soil microflora to favor
biological pest control. Lastly, polyethylene films used in solarization can serve as mulch to reduce weeds when
maintained as a row cover throughout the growing season (Stapleton 1994, Katan and DeVay 1991).
-------
Soil Serialization in California Orchards
Unlike methyl bromide, soil solarization can be used effectively as both a pre- and post-plant treatment in many
California (and other regional) orchards. Clear polyethylene films are typically used in pre-plant orchard treatments,
while black polyethylene films (which achieve slightly lower temperatures depending on the thickness of the film) are
most often used on newly planted or established orchards to gain the benefits of solarization while preventing heat
damage to trees (DeVay 1996, Stapleton et al. 1993). Orchard trees have also been successfully established using clear
polyethylene mulch as a pre-plant treatment in cooler areas of the San Joaquin and Sacramento Valleys (Stapleton and
DeVay 1985, Stapleton et al. 1989).
Solarization causes physical, chemical, and biological changes in the soil by raising soil temperatures from 2-
I5°C above the temperatures of untreated soil. Soil solarization is successful because most plant pathogens and pests
are mesophilic or unable to survive for long periods at temperatures above 37 °C. Pathogens may be killed either
directly by the heat or are weakened by sublethal heat to the extent that they are unable to damage crops (DeVay 1996).
The heat sensitivity of these organisms is directly linked to an upper limit of fluidity in cell membranes, which lose their
ability to function at high temperatures. Other methods of inactivation affected by solarization include sustained
interference with enzyme systems, especially the respiratory process (DeVay et al. 1990).
In addition to providing pest and pathogen control, solarization conserves water and promotes growth in new
orchards or replanted trees in temperate, as well as arid climates (Stapleton et al. 1993, 1991, and 1989, Duncan et al.
1992, Stapleton and Garza-Lopez 1988, Katan 1987, Stapleton and DeVay 1986). Experiments have confirmed that
polyethylene films used for solarization conserve irrigation water under arid and drought conditions by preventing
evaporation and trapping water. Furthermore, there is significant evidence that even in hot and arid climates, non-
mature deciduous fruit and nut trees (e.g., almond, peach, apricot) may be established with no more than pre-plant
irrigation and perhaps two or three carefully timed irrigations later in the season if necessary (Stapleton et al. 1993,
Duncan et al. 1992, Stapleton et al. 1989, Stapleton and Garza-Lopez 1988). Solarization may also result in an
increased growth response (as evidenced by increased trunk diameters) and yield in orchard trees, by increasing the
availability of plant nutrients and the relative populations of beneficial organisms (i.e., rhizosphere bacteria (such as
Bacillus spp. wA-Pseudomonasspp.), Trichaderma spp., actinomycetes, and rnycorrhizal fungi) (Stapleton 1996, Katan
and DeVay 1991, Stapleton et al. 1989, Stapleton and Garza-Lopez 1988, Pullman et al. 1984).
Solarization Techniques
The effectiveness of solarization and the heat dosages achieved during solarization depend on soil moisture and
texture; air temperature (maxima, minima, and duration); season; length of day; intensity of sunlight; wind speed and
duration; and the type, color, and thickness of the plastic (Katan and DeVay 1991,DeVayetal. 1990). Orchard trees
create discontinuities in the field so that application of continuous plastic films must either be done manually or
semimechanically using plastic-laying machinery. Plastic strips are cut and hand applied around tree bases and then (in
the case of semimechanical applications) connected to sheets of machine-applied plastic between tree rows with heat-
resistant glue or narrow bands of soil (Pullman et al 1984). While not as effective as the above, in some cases, wide
strips of plastic are only placed between tree rows (strip mulching) or are applied by piercing films over young tree
shoots in newly planted orchards (DeVay 1996, Katan and DeVay 1991).
In pre-plant orchard treatments, a layer of polyethylene film is applied to the soil prior to planting and is left in
place for 4 to 6 weeks or more during the hot season. In post-plant treatment, however, polyethylene films are applied
after planting and can remain in place for up to two years (McKenry 1996). Proper soil preparation is also essential to
provide a smooth, even surface for the film and allow water to penetrate evenly and deeply into the soils (Stapleton
1996). To maintain proper soil moisture, orchards are irrigated 1 to 4 days prior to applying the plastic tarp.
Alternatively, irrigation lines can be installed beneath the tarp and utilized as necessary (Katan 1981). While not
currently field feasible, double layers of plastic can simulate solarization under glasshouse conditions, and will result in
even greater temperature increases in soils (i.e., 3 to 10°C higher then that achieved under a single layer of plastic)
(DeVay et al. 1990, DeVay 1996). Regardless of the technique used, the beneficial effects of solarization may persist
for up to 2 years or more after the plastic is removed (Katan and DeVay 1991, DeVay et al. 1990).
-------
Serialization Research In Orchards
A number of researchers have reported successful pre- and post-plant applications of soil solarization or other
film mulching techniques for management of soilbome pests and pathogens in orchards. For example, solarization is
known to control Verticillium wilt in pistachios (Ashworth and Gaona 1982) and olive trees (Tjamos et al. 1991, Katan
and De Vay 1991), almonds and apricots (Stapleton, et al. 1993) and white root rot in apple trees (Freeman et al. 1990,
Sztejnberg et al. 1987). Solarization is also effective against certain nematode species and non-specific replant diseases
in other crops, such as almonds, peaches, and walnuts (Abu-Gharbieh et al. 1991, Stapleton et al. 1989, Jenson and
Buszard 1988, Stapleton and DeVay 1984,1983). Although solarization is an effective treatment method for a wide
variety of orchard crops, crop response to solarization varies. For example, apricots are very responsive to soil
solarization in that they are only susceptible to Verticillium wilt during the first 4 to 6 years of growth, therefore only one
solarization treatment is required. Other orchard trees (i.e., certain cultivars of olive and pistachio); however, are
susceptible to Verticillium wilt both in the first few years of growth and as mature trees and therefore must be treated
repeatedly (Stapleton etal. 1993).
Although solarization can be a viable alternative to methyl bromide in orchards, there are limitations to it use.
While solarization is just as effective as methyl bromide in the upper layers of the soil, the combined high heat levels and
duration are often not adequate to penetrate into deeper soil levels (Stapleton 1995, De Vay 1995). This may impact
overall yields when this is the only pest control tool utilized. Recent research; however, suggests that soil solarization, in
combination with other alternatives to methyl bromide (e.g., Telone" or Vapam*) offers an "additive" effect that actually
increases the efficacy of both chemical alternatives and solarization compared to their stand-alone uses. Although
solarization is most effective in warm, arid climates; clear, thicker, and at even double layers of plastic (not currently
feasible) can be used to achieve lethal levels of heat in more temperate regions (Katan and DeVay 1991). Although
solarization has been successfully used in mature orchards, excessive shading by mature tree canopies may limit the
effectiveness of this treatment under certain conditions (Stapleton et al. 1993, Stapleton et al. 1989).
Reducing Chemical Usage and Costs
Solarization can be a cost-effective technique and when the additional benefits of increased growth response,
water conservation, and enhanced nutrient availability are considered, the economics are further improved (Stapleton
1994, Katan and DeVay 1991). Furthermore, solarization can be (and sometimes must be) combined with other
chemical, physical, and biological methods (e.g., fertilizers, soil amendments, integrated pest management strategies,
limited pesticide use, and biological control agents) for enhanced management of soilborne pests and pathogens (DeVay
1996, Katan and DeVay 1991).
The cost of solarization varies depending on the thickness of the plastic, areas of soil coverage (partial vs.
complete coverage), irrigation methods, and the method of plastic application, connection, and removal (Pullman,
1984). For example, strip mulching can reduce solarization costs to two thirds the cost of full tarping (McKenry 1996).
General cost estimates for solarization compared to methyl bromide fumigation are provided in Table 1 below. As
mentioned above, chemical treatments can improve the control levels achieved with solarization. Therefore,
representative chemical costs for Telone" or Vapam* have been included in the cost ranges presented in the table below.
As shown, reduced chemical usage and cost savings can be achieved by using solarization for controlling soil-borne
pests and pathogens. The direct costs of soil solarization can be one-half that of methyl bromide treatments (DeVay
1995; Stapleton 1995). Both this technique and the use of methyl bromide will require consideration of costs associated
with the disposal or recycling of the plastic tarps.
-------
Table 1. The Comparative Costs of Solarization and Methyl Bromide Fumigation
Cost Factor
Tarp
Labor
(including tarp removal)
Chemical
Total
TFeatment#lt Solaiization
-------
Katan 1981." Solar heating (solarization) of soil for control of soilborne pests." J. Katan. Annual Review of
Phytopathology. Volume 19, pp. 211-36.
Katan 1987. Soil Solarization. J. Katan. In: Innovative Approaches to Plant Disease Control. John Wiley & Sons, Inc.
pp. 77-105.
Lakes Agrisales 1995 (February). Personal communication. Lykes Agrisales. Price Quote for Telone C-17, Methyl
Bromide, and Tillam.
McKenry 1996 (September). Personal Communication. M.V. McKenry. University of California. Kearney
Agricultural Center. Parlier, CA.
Pullman, G.S. et al. 1984. Soil Solarization, A Nonchemical Method for Controlling Diseases and Pests. G.S.
Pullman, J.E. DeVay, C.L. Elmore, and W.H. Hart. Cooperative Extension Publication 21377, University of
California.
PolyWest 1996 (June 15). Polyon Mulch and Low Tunnel Pricing. PolyWest. San Diego, CA.
Stapleton 1996 (September). Personal communication. James J. Stapleton. Statewide Integrated Pest Management
Project, University of CA Kearney Agricultural Center.
Stapleton 1995 (January 20). Personal communication. James J. Stapleton. Statewide Integrated Pest Management
Project, University of CA Kearney Agricultural Center.
Stapleton 1994. "Solarization as a framework for alternative soil disinfestation strategies in the interior valleys of
California." J. J. Stapleton. hi Proceedings of the 1994 Annual International Research Conference on Methyl Bromide
Alternatives and Emissions Reductions. Kissimmee, FL.
Stapleton and DeVay 1986. Differentiation of Verticillium dahlias pathotypes and Cotton Tolerance to Wilt as
Affected by Stem-puncture Inoculum Concentration (Abstract). J.J. Stapleton and J.E. DeVay. Phytopathology.
Volume 76, p. 1107.
Stapleton and DeVay 1985. Soil Solarization as a Post-plant Treatment to Increase the Growth of Nursery Trees
(Abstract). J.J. Stapleton and J.E. DeVay. Phytopathology. Volume 75, p. 1179.
Stapleton and DeVay 1984. Thermal Components of Soil Solarization As Related to Changes in Soil and Root
Microflora and Increased Plant Growth Response. J.J. Stapleton and J.E. DeVay. Phytopathology. Volume 74, p.p.
255-259.
Stapleton and DeVay 1983. Response of Phytoparasitic and Free-living Nematodes to Soil Solarization and 1,3-
dichloropropene in California. J.J. Stapleton and J.E. DeVay. Acta Horticulture. Volume 255, p.p. 161-168.
Stapleton and Garza-Lopez 1988. Mulching of Soils with Transparent (Solarization) and Black Polyethylene Films to
Increase Growth of Annual and Perennial Crops in Southwest Mexico. Tropical Agriculture Trinidad. Volume 65,
pp. 29-33.
Stapleton et al. 1993. Establishment of Apricot and Almond Trees Using Soil Mulching with Transparent
(Solarization) and Black Polyethylene Film: Effects on Verticillium Wilt and Tree Health. J.J. Stapleton, E.J.
Paplomatas, R.J. Wakeman, and J.E. DeVay. Plant Pathology. Volume 42, pp. 333-338
Stapleton et al. 1991. Use of hi-season Polyethylene Mulching for Establishment of Deciduous Fruit and Nut Trees
in the San Joaquin Valley: Effects on Pathogen Numbers and Tree Survival. Proceedings of the National Agricultural
Plastics Congress. Volume 23, pp. 260-265.
-------
Stapleton et al. 1989. Use of Polymer Mulches in Integrated Pest Management Programs for Establishment of
Perennial Fruit Crops. J.J. Stapleton, W.K. Asai, and J.E. DeVay. Acta Horticulture. Volume 255, pp. 161-168.
Sztejnberg et al. 1987. Control ofRosellinia necatrix in Soil and Apple Orchard by Solarization and Trichoderma
harzianum. Plant Disease. Volume 71, pp. 365-369.
Tjamos et al. 1991. Recovery of Olive Trees With Verticillium Wilt After Individual Application of Soil Solarization
in Established Olive Orchards. Plant Disease. Volume 75, pp. 557-562.
State of California 1992. Pesticide Use Report, Annual 1992.
-------
&EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1996
Protection Agency
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Integrated Pest Management and Soil Pest Control Technologies
In California Vineyards
Integrated Pest Management (IPM) practices which do not utilize methyl bromide have begun to replace the
use of this fumigant for the control of soilbome pests in a number of California vineyards. Currently, only about
half of California's vineyard acreage are fumigated with methyl bromide as a preplant treatment, hi fact, large-scale
California grape producers, including Fetzer Vineyards, Savage Island Farms, Soghomonian Farms, Steven Pavich,
and many other vineyards in the Lodi-Woodbridge region are succesfully using IPM practices to grow grapes
profitably without methyl bromide. Furthermore, it is likely that the use of IPM practices will continue to expand as
the research base increases, the market for environmentally friendly products increases, and on-farm demonstrations
facilitate technology transfer.
Currently, field research, on-farm efficacy
studies, and economic analyses of various alternatives
are helping to accelerate the transition from methyl
bromide soil fumigation to IPM practices. For
example, the Lodi-Woodbridge Winegrape
Commission (LWWC), working under grants from the
California Energy Commission, the Kellogg
Foundation, and California's Department of
Environmental Protection, are studying the energy
costs associated with conventional and sustainable
fanning systems, the implementation of IPM strategies
region-wide, and the education and promotion of
existing IPM techniques to growers in California
(Lanchester 1996). Further, scientists at the Kearney
Agricultural Station are studying metam sodium to
improve its efficacy for nematode control (Peacock
1995, Westerdahl 1995). These and other research
and implementation efforts will help to reduce the use
of methyl bromide in California's vineyards.
Benefits of IPM
IPM reduces grower's vulnerability to regulatory
actions on pesticides and on pest resistance to
chemical controls
Growers already practicing IPM can serve as
mentors and provide site demonstrations to other
farmers
The research base for IPM techniques is
increasing for products derived from
environmentally friendly production practices is
increasing
The less chemical pesticides used, the fewer
residues in soil and crops
Overview of Methyl Bromide Use in California Vineyards
Approximately 10,000 California farms produced 89 percent of the 11 billion pounds of grapes harvested in
the U.S. in 1992 (U.S. Department of Commerce 1994). While the number of acres devoted to grape production in
California has declined slightly over the past decade, production has nearly doubled (CAS 1993), and in 1992 the
California grape crop was valued at $1.7 billion (Liebman and Daar 1995).
Although grape vines are perennial crops and typically remain in production for many years, vines grown
for commercial production are periodically replanted to maintain high productivity and uniform fruit quality. In
conventional grape production, soil pest control technologies are used primarily to prepare soils for replanting (NRC
1989, Peacock 1995). Three to five years after the new rootstock is planted, grape vines begin to reach their
-------
productive potential; on average, vines remain in peak production for approximately 20-25 years although some
produce for up to 40 years (NRC 1989, CAN, et al. undated, Peacock 1995).
Grape production is the third largest use of methyl bromide for soil fumigation in California (Liebman and
Daar 1995). In 1992, approximately 5,600 acres of vineyard land, or 45 percent of the area planted with wine, raisin
or table grape crops, were fumigated with approximately 900 metric tons of methyl bromide (Liebman and Daar
1995, EPA 1994). California vineyards account for about 4 percent of the total U.S. methyl bromide consumption,
10 percent of all California soil fumigant application, and 1.3 percent of world wide use (EPA 1994).
Methyl bromide (combined with chloropicrin) is applied prior to planting vineyards in order to control a
variety of soilborne pathogens, nematodes, insects, and weeds (SCEPA 1993, NRC 1989). Primary target pests are
nematodes; however, phylloxera and oak root fungus are also a concern in many vineyards (Westerdahl 1995).
Fumigation primarily occurs on soils that previously supported grape-vines, orchard trees, or native oaks and are
scheduled to be replanted into vineyards. Because these soils may contain insects and pathogens harbored by the
remains of the previous crop, fumigation is often performed to control soilborne pathogens prior to re-planting.
Methyl bromide is usually distributed to depths of four feet by tractors through hollow tubes driven into the soil.
Application rates are typically 300 to 500 pounds per acre. Although tarps are often used to maintain fumigant
concentrations, sometimes the use of tarps is omitted to reduce costs by up to $600 per acre. In some instances,
fumigation is not practiced prior to replanting, especially if pests are absent or are present in low numbers (e.g., in
some coastal areas or in parts of the San Joaquin Valley) (Liebman and Daar 1995).
In addition to its impact on stratospheric ozone, there are several reasons to find alternatives to methyl
bromide use in vineyards. First, material and application costs for methyl bromide can range anywhere from $600-
$1,500 per acre. Second, methyl bromide, as well as other chemical fumigants, are restricted use pesticides that can
not be applied near urban areas, on unsuitable terrain, or in areas where soils are damp. Third, grower aversion to
methyl bromide and availability of alternatives has tended to decrease use over the past few years (Liebman 1994,
DPR 1994a, DPR 1994b). For example, methyl bromide applications are often ineffective in controlling vineyard soil
pests due to an inability to penetrate deep into soils which are heavy, coarse, or poorly prepared. Lastly, growers are
concerned that methyl bromide fumigation will stunt plant growth by destroying beneficial mycorrhizal fungi
(Liebman and Daar 1995).
IPM as a Replacement for Methyl Bromide
Research indicates that grapes can be produced in the absence of methyl bromide without jeopardizing
quality or profitability (Liebman 1994). A majority of the grape industry in California has turned to integrated pest
management (IPM) practices as a long-term approach for managing pests. IPM techniques rely on combining
biological, cultural, and chemical tools in a way that minimizes economic, health, and environmental risks
(Lanchester 1996). Pesticides are used only when needed and the least toxic formulations and lowest dosages
required for effective pest suppression are encouraged (Liebman and Daar 1995).
Growers practicing IPM rely on a variety of pest control methods, including the use of chemical alternatives,
resistant rootstocks, crop rotations, cover crops, biological controls (e.g., manures, compost or mineral adjustments).
Other farmers produce grapes using organic fanning practices. Some growers forgo preplant fumigation and rely
instead on post-plant pesticides such as carbofuran (Furadan™), fenamiphos (Nemacur™), and sodium
tetrathiocarbonate (Enzone™), or other chemical alternatives such as dazomet (Basamid™), 1,3-dichloropropene
(Telone™) and metam sodium (Vapam™), which may be used in combination with non-chemical techniques to
increase then- effectiveness in controlling soil pests. The use of these methods vary, depending on the pest species
present, soil type, topography, grape varieties grown, market conditions, land values and ownership, access to
capital, regulatory restrictions, and personal philosophy. In general, these activities reduce the population size and
impact of pests and improve the plant vigor and ability to tolerate pest damage (Liebman and Daar 1995). Examples
of growers that have successfully used non-chemical and least toxic chemical IPM techniques to produce grapes
profitably with out the use of methyl bromide include:
-------
• Fetzer vineyards, in southern Mendocino county, produces organic grapes on 455 acres. After a
four-year transitional period during which methyl bromide was not applied, the vineyard has
achieved yields that are "competitive" and the prices received are "comparable" (CAN, et al.
undated).
• Savage Island Farm produces table grapes in the San Joaquin Valley. New vines are planted 1 to
1.5 years after old vines are removed, reducing the fallow period with the use of deep-rooted cereal
rye and vetch cover crops. Nematodes are not considered a serious problem because applications
of raw green manure and compost help to suppress the populations (Liebman and Daar 1995).
• Soghomonian Farms, near Fresno, produces organic wine, table, and raisin grapes. Nematode
damage is countered by adding manure to the soil and replanting damaged areas. Also, land is
allowed to lie fallow for one year before re-planting (Liebman and Daar 1995).
• Steven Pavich plants both organic and conventional grape acreage in California and Arizona. He
relies on field monitoring and application of preplant treatments only when necessary.!!!
Additionally, mere is a program for soil building including cover cropping and applications of
organic, mineral and beneficial microbe amendments (Liebman and Daar 1995).
The most promising alternatives include a variety of chemical and non-chemical alternative technologies
including alternate fumigants, pasteurizing soil with hot water, soil solarization, resistant rootstocks, soil
amendments, biological control, and disease suppressive cover crops (Liebman and Daar 1995):
Chemical Alternatives. The most promising chemical alternative technologies include fumigation with
Telone™ (1,3-D) and metam sodium. These compounds have been shown to effectively manage a variety of
the soil pests currently controlled with methyl bromide. Additional research will help to enable growers to
implement application techniques with increased effectiveness in managing soil pests (Peacock 1995,
Westerdahl 1995, University of California 1992).
Pasteurizing with Hot Water. This technique involves applying hot water into the soil at a depth of 12
inches and using a rotovator to distribute the heat through the top foot of soil. This procedure not only
manages pests but also irrigates the fields. This has yet to be fully tested on the deep rooted pests found in
vineyards.
Resistant Rootstocks. The use of grape rootstocks that show tolerance or resistance to pest species (Flaherty
et al. 1992) and have acceptable vigor and viticultural properties can be used to help replace the use of
methyl bromide. Resistant rootstocks are a promising alternative to methyl bromide (Peacock 1995) and
there has been remarkable effort in California to develop grape rootstocks that are tolerant to nematode
infestation in a variety of climates, soils, and pest pressures (University of California 1992, Peacock 1995).
Soil Management. Cultural controls and the addition of soil amendments (e.g., minerals, compost, manure,
and green matter) that improve and strengthen root growth and help grape vines become established more
quickly are also effective pest management techniques. Efforts to enhance natural biological controls in the
absence of fumigation can also be an effective approach to managing soil pests (e.g., oak root rot is
controlled by naturally occurring soilborne fungi in me Trichoderma genus in many California vineyards).
Cover Crops and Crop Rotation. Cover crops are used to reduce soil pathogens (mainly nematodes) and to
provide organic matter mat will lead to improved yields (Peacock 1995). Crop rotation can also be an
effective method of suppressing damage caused by soilborne pests, but there are costs associated in terms of
keeping land out of perennial crops for a period of time.
Solarization. Solarization is a method in which clear plastic is laid on the soil surface to trap solar radiation
and heat the soil. Although the method is particularly effective in hot areas such as the Central Valley
(Katan and DeVay 1991, Chellemi et al. 1994), to date, this technique has not been widely studied or
utilized for grape production.
-------
Costs of IPM Treatments
Development of cost estimates for IPM treatments is limited by the diversity of possible techniques to
managing soil pests using an integrated approach. In general, an IPM approach could include using an alternative
fumigant, increasing the use of soil amendments and cover crops, paying increased attention to soil conditions (i.e., pest
populations), managing cultivation and irrigation schedules more effectively, and using rootstocks with resistance to soil
pests. In addition, the selected approach and the resulting treatment cost will be affected by the local site conditions.
Given these limitations, Table 1 presents a cost comparison of two methods that could be used to manage soilborne
pests when establishing a vineyard. As shown, the up-front costs of the IPM treatment are estimated to be
approximately $300 less than the methyl bromide treatment, suggesting that IPM would be an viable alternative to
methyl bromide. In addition, future treatments, including periodic scouting, soil testing, spot nematicide treatments,
additional soil amendments, and the use of cover crop may be used to maintain or increase the effectiveness of the
IPM approach. Although not all of these activities may be required on an annual basis, they could increase future per
acre treatment costs by about $50 to $200 annually.
Table 1. Comparison of Soil Treatment Costs for Establishing a Vineyard
Treatment
Methyl Bromide
IPM
Estimated Cost
1,110 to $2,010
$1,670
Cost Components
Fumigation with methyl bromide
Soil Amendments
Cover Crops, Cultivation, Mowing, and Herbicides
Fumigation with metam sodium
Soil Amendments
Cover Crops, Cultivation, Mowing, and Herbicides
$600 -$1,500
$400
$110
$ 1,000
$500
$170
Sources: Howe 1994, Klonsky 1992a, Klonsky 1992b, McKenry 1995, Smith 1992, Verdegall 1994.
References
CAN, et al. undated. California Action Network et al. Into the Sunlight, Exposing Methyl Bromide's Threat to the
Ozone Layer.
CAS. 1993 (March). California Agricultural Statistics. California Fruit & Nut Statistics, 1983-92.
DPR. 1994a (May 2). Methyl bromide suggested soil injection fumigation permit conditions. California EPA,
Department of Pesticide Regulation Advisory to County Agricultural Commissioners. DPR Document No. ENF 94-
019.
DPR. 1994b (June 2). Updates to the soil injection and greenhouse suggested methyl bromide permit conditions.
California EPA, DPR Advisory to County Agricultural Commissioners, DPR Document No. ENF 94-025.
Chellemi. 1994. "Integrated pest management for soilborne pests of tomato (Abstract)." D.O. Chellemi, S.M.
Olson, R. McSorley, D.J. Mitchell, W.M. Stall, and J.W. Scott. In: MBAO, pp. 25-1,2.
EPA. 1994. Methyl Bromide Consumption Estimates. U.S. Environmental Protection Agency, Stratospheric
Protection Division, Washington, D.C. May 3, 1994.
-------
Flaherty, et al. 1992. Grape Pest Management, 2nd ed. Flaherty, D.L., L.P. Christensen, W.T., Lanini, J.J.
Marois, P.A. Philh'ps, and L.T. Wilson (eds.). University of California, Division of Agriculture and Natural
Resources. Oakland, California.
Howe. 1994 (October). "Lodi's Dynamic Duo Cuts Chemicals by 80%." Kenneth Howe. In Farmer to Farmer.
Community Alliance with Family Farmers Foundation. Davis, California.
Katan and DeVay. 1991. Soil Solarization. J. Katan and J.E. DeVay. CRC Press. Boca Raton, Florida.
Klonsky, et al. 1992a. Sample Costs to Produce Organic Wine Grapes in the North Coast: with resident vegetation.
K. Klonsky, L. Tourte, and C. Ingels. Department of Agricultural Economics, Cooperative Extension, University of
California. Davis, California.
Klonsky, et al. 1992b. Sample Costs to Produce Organic Wine Grapes in the North Coast: with and annually sown
cover crop. K. Klonsky, L. Tourte, and C. Ingels. Department of Agricultural Economics, Cooperative Extension,
University of California. Davis, California.
Lanchester. 1996 (July 23). Personal communication. Lanette Lanchester, EPM Coordinator, Lodi-Woodbridge
Winegrape Commission. Lodi, California.
Liebman. 1995 (January 18). Personal communication. Jamie Liebman, Bio-Integral Resource Center. Berkeley,
CA.
Liebman. 1994 (November). James A Liebman. Integrating Research and Practice: Implementing Alternatives to
Methyl Bromide Soil Fumigation in California Agriculture. 1994 Annual International Research Conference on
Methyl Bromide Alternatives and Emissions Reductions. November 13-16. Kissimmee, Florida.
Liebman and Daar. 1995 (February). "Alternatives to Methyl Bromide in California Grape Production," The JPM
Practitioner: Monitoring the Field of Pest Management, Vol. XVn, No. 2.
McKenry. 1995. "First-year evaluation of tree and vine growth and nematode development following 17 pre-plant
treatments." M. McKenry, T. Buzo, and S. Kaku. hi: MBAO.
NRC. 1989. National Research Council. Alternative Agriculture. National Academy Press. Washington, D.C.
Peacock. 1995 (January 18). Personal communication. William Peacock, Tulare County Farm Advisor. Visalia,
CA.
SCEPA. 1993. State of California, Environmental Protection Agency. Pesticide Use Report Annual 1992 Indexed by
Commodity. Department of Pesticide Regulation. Sacramento, CA.
Smith. 1992. Sample Costs to Establish a Vineyard and Produce Wine Grapes in Sonoma Counry-1992.. R. Smith,
K. Klonsky, P. Livingstone, Department of Agricultural Economics, Cooperative Extension, University of California,
Davis. California.
University of California. 1992. UCIPM Pest Management Guidelines. Division of Agriculture and Natural
Resources. Publication 3339.
U.S. Department of Commerce. 1994 (October). 1992 Census of Agriculture. Economics and Statistics
Administration, Bureau of the Census.
Verdegall, et al. 1994. Sample Costs to Establish a Vineyard and Produce Wine Grapes: Cabernet Sauvignon
Variety & Drip Irrigated in the Lodi Appellation of Sacramento and San Joaquin Counties. P. Verdegall, K.
Klonsky, and P. Livingston. Department of Agricultural Economics, Cooperative Extension, University of
California. Davis, California.
-------
Westerdahl. 1995 (January 18). Personal communication. Becky Westerdahl, Extension specialist-Applied
Nematology and IPM, University of California. Davis, California.
-------
&EPA
United States
Environmental
Office of Air and Radiation
(6205-J)
December 1996
Protection Agency
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Heat Treatments (Hot-water Immersion, High Temperature Forced Air, Vapor Heat)
As Alternative Quarantine Control Technologies for Perishable Commodities
Hot-water immersion, high temperature forced air, and/or vapor heat are three heat treatment technologies
that can be used for post-harvest insect control for perishable commodities such as fresh fruits (e.g., mangos, papaya,
persimmon, citrus, bananas, carambola), fresh vegetables (e.g., peppers, eggplant, tomatoes, cucumber, and zucchini
squash), bulbs, and cut flowers (Tsang et al. 1995, UNEP 1994, 1992, APHIS 1993, Hansen et al. 1992). Heat
treatments for disinfestation of fruit have been used since 1929 when Baker and co-workers developed a vapor heat
treatment against the Mediterranean fruit fly (Couey 1989). However, interest in heat treatments waned with the
development of chemical fumigants, which could be applied cheaply and easily. Today, with the increasing cost of
developing new chemicals and regulatory restrictions on existing ones, interest in heat disinfestation has been revived
(Couey 1989).
Currently, methyl bromide is the most commonly used fumigant for controlling quarantine pests on
perishable commodities; however, methyl bromide can only be used on certain commodities at specific temperatures
and dosages because some commodities are highly sensitive to its use (e.g., certain tropical fruits imported from
Hawaii) (Kara et al. 1994). The percentage of global consumption of methyl bromide used to treat perishable
commodities is estimated to be 8 percent or 6,500 tonnes (UNEP 1994). Almost half of the methyl bromide used for
commodity treatments are for disinfestation of
exported fruits and nuts (e.g., papaya, mango, dried
fruits, grapes, berries, nectarines, cherries, apples,
walnuts, and pistachios). Methyl bromide
fumigation is also the predominant treatment used
for pests in vegetable shipments (e.g., cucumbers,
squash, tomatoes) imported into many countries
(UNEP 1994). Lastly, methyl bromide fumigation
is widely used by many countries as a standard
quarantine treatment for various arthropod-infested
flowers and foliage. Across these uses, methyl
bromide application rates vary depending on the
temperature, exposure period, and commodity
(Folwell 1996).
Heat treatment technologies are currently a relatively simple, non-chemical alternative to methyl bromide
that can kill quarantine pests (insects and fungi) in perishable commodities, as well as control some postharvest
diseases. Unlike methyl bromide, heat treatments do not pose significant health risks from chemical residues and, as
a result, are more appealing to consumers than methyl bromide fumigation (Couey 1989). Furthermore, heat has
been approved as a quarantine treatment by the U.S. Department of Agriculture's (USDA) Animal and Plant Health
Inspection Service (APHIS) against pests (mainly fruit flies) for several perishable commodities.
In most cases, heat treatments are performed by the country of origin before a product is exported. The
temperature, duration, and application method is both cultivar and commodity specific and must be very precise to kill
pests without damaging the commodity. Heat is unsuitable for highly perishable products such as asparagus,
nectarines, avocados, or leafy vegetables as their shelf-life and marketability is reduced (UNEP 1994, Couey 1989).
Fruit responses to heat varies depending on the condition of the fruit prior to treatment (Mitcham et al. 1994), the
commodity concerned, the temperature and duration of treatment, as well as the mode of heat application (i.e., hot air
vs. water). If not properly applied, heat treatments (as well as methyl bromide treatments) may result in commodity
Benefits of Heat Treatment
I/ Provides effective insecticidal andfungicidal
action
• Easy to apply
• No environmental harm
• Absence of chemical residue on treated fruits and
vegetables
-------
damage, which typically is manifested as browning fruit surfaces, uneven ripening, and breakdown of the fruit flesh.
However, beneficial effects of heat treatment, include reduced susceptibility to chilling injury in avocados and
persimmons (Lay-Yee 1994).
Heat Treatment Methods and Research
The majority of quarantine research on heat treatment methods for perishable commodities is conducted by
the USDA, Agriculture Research Service (ARS) in Florida, Texas, Washington State and Hawaii. Many studies have
shown that heat treatments do not affect market quality of the commodity and can meet the mandated USDA Probit 9
security level of quarantine pest control, which allows no more than 3.2 survivors out of 100,000 larvae (99.9968
percent mortality) at the 95% confidence level (Baker 1939, McGuire 1991), when the core of the fruit reaches a
sufficiently high temperature. Heat treatment methods, as well as approved quarantine heat treatments and on-going
research on potential quarantine heat-treatments for perishable commodities, are discussed below.
Hot-Water Immersion: Hot-water immersion consists of submerging the commodity in a hot-water bath at a
specific temperature for a specified time based on the commodity being treated and the pests that may be present
(APHIS 1993). For perishable food commodities, the mandated probit 9 level of fly control can be achieved by
heating the core of the fruit to 43-46.7°C (109.4-116.1°F) with exposure times varying from 35 to 90 minutes
(APHIS 1993, Gould 1988, Gould and Sharp 1992, Hallman 1989, Sharp 1986, 1990, Sharp and Picho-Martinez
1990, Sharp et al. 1988, 1989, 1989a, 1989b, Sharp and Spalding 1984, UNEP 1994). Variations are noted for
different commodities, pest species, and life stages of insect pests. Hot-water is an effective heat transfer medium
and, when properly circulated through the load of fruit, quickly establishes a uniform temperature profile (Couey
1989). Hot-water immersion also has the additional benefit of controlling postharvest microbial diseases such as
anthracnose and stem end rot (Couey 1989, McGuire 1991). Immersion of non-food perishable commodities (such as
cut flowers and bulbs) in hot water (43.3-49°C (109.9-120.2°F)) for 6 minutes to 1 hour is effective in destroying
insect pests while maintaining product quality (Kara et al. 1994, UNEP 1994).
Hot-water immersion is currently used to successfully treat mangos infested with the Mediterranean fruit fly
and several different Anastrepha species of fruit fly before importation into the United States from Mexico, the
Caribbean, and Central and South America (APHIS 1993). Research performed by ARS on mangos, which are
relatively resistant to heat damage, led to approval by USDA-APHIS of hot-water immersion quarantine treatments
for mangos infested with fruit fly immatures (Sharp and Picho-Martinez 1990, Sharp and Spalding 1984, Sharp 1986,
1988, Sharp et al. 1988, 1989, 1989a, 1989b). Successful hot-water immersion quarantine treatments against fruit
flies were also developed for papayas (Couey and Hayes 1986), guavas (Gould and Sharp 1992), and bananas
(Armstrong 1982), however, these treatments are not currently approved by USDA-APHIS. Hot-water immersion
treatment is not recommended for grapefruit, stone fruits (plums, nectarines and peaches), or carambolas (star fruit),
because this treatment does not produce probit 9 security and/or produces unacceptable fruit damage in these specific
commodities (Hallman 1989, 1991, Hallman and Sharp 1990a, Sharp 1985, 1990). Hot-water immersion of narcissus
bulbs is also an APHIS-approved treatment for controlling the Stenearsonemus laticeps mite (UNEP 1994). A
promising potential hot-water immersion treatment has also been developed for cut flowers and foliage (Kara et al.
1994).
High Temperature Forced Air: Recirculated air that has been heated and humidified can be forced over fruit
surfaces to raise the temperature to a level that is lethal to target pest species. Heated air treatments of 40-50°C
(104-122°F) (usually at four incrementally increased temperatures) for less than eight hours are becoming more
common for fruit fly control in tropical commodities (Armstrong et al. 1989, Gaffney and Armstrong 1990, Mangan
and Ingle 1992, UNEP 1994, Sharp 1989a, 1992, Sharp and Gould 1994, Sharp and Hallman 1992). Condensation
on fruit surfaces or in the treatment chamber is prevented by keeping the dew-point temperature 2-3 °C below the dry-
bulb temperature throughout the duration of the test. This precise control of temperature and relative humidity is
advantageous because it prevents condensation inside the treatment area and on the fruit surface thus preventing fruit
desiccation and scalding (Gafrhey and Armstrong 1990, Sharp et al. 1991).
Fruits shown to tolerate treatment with hot air are mango (Mangan and Ingle 1992, Miller et al. 1991, Sharp
1992, Sharp et al. 1991), grapefruit (McGuire 1991a, Sharp 1989a, Sharp and Gould 1994), navel orange (Sharp and
McGuire 1996), carambola (Sharp and Tollman 1992), persimmon (Lay-Yee 1994), and papaya (Armstrong et al.
1989). Hot air is not recommended for avocado, lychee, and nectarine at treatment controlled temperatures needed to
disinfest them of quarantine pests (Sharp 1994, Kerbel et al. 1987). USDA-APHIS has approved forced air
-------
treatments for grapefruit, papaya, and mango (APHIS 1993). Fruit flies of concern are Mexican fruit fly in grapefruit
from Mexico; Mediterranean fruit fly, oriental fruit fly, and melon fruit fly in papaya from Hawaii; and Mexican fruit
fly, West Indian fruit fly, and black fruit fly in mango from Mexico (APHIS 1993).
Vapor Heat: Vapor-heat quarantine treatment uses heated air saturated with water vapor to heat perishable
food commodities to a specified temperature and holds that temperature for a specified period to ensure that all pests
(such as tephritid fruit fly immatures) within the commodity are killed (APHIS 1993, Hallman 1990, Hallman et al.
1990). Typically, the pulp temperature of the commodity is raised by the saturated water vapor to 43.3-44.4°C
(109.9-11.9°F) during a period of 6 or 8 hours and then held at the required temperature for another 6 or 8 hours
(APHIS 1993). For several varieties of cut flowers and foliage, vapor heat treatments of 1-2 hours were greater than
99.7 percent effective in controlling pests (Hansen et al. 1992).
Vapor heat (greater than 90 percent relative humidity) is approved by USDA-APHIS for treatment of
Clementine, grapefruit, orange, and mangos imported from Mexican fruit fly infested areas and for bell peppers,
eggplants, papayas, pineapples, tomatoes, zucchini, and squash imported from areas infested with Mediterranean,
Oriental, and Melon fruit flies (APHIS 1993). Vapor heat was found to be effective as a potential quarantine
treatment for carambola (Hallman 1990), grapefruit (Miller et al. 1991), codling meth in sweet cherries (Neven and
Micham 1996), against the Caribbean fruit fly for tropical cut flowers as well as on foliage against aphids, soft and
armored scales, mealybugs, and thrips (Hansen et al. 1992, UNEP 1994).
Costs
Hot-water immersion, high temperature forced air, and vapor heat are effective quarantine alternatives to
methyl bromide fumigation for fruits and vegetables that are not susceptible to heat damage, particularly tropical and
subtropical commodities, with proven efficacy against various pests and diseases. In general, methyl bromide
treatment systems can range in cost from $21,000 to as much as $291,000, depending on the commodity and
quantities being treated (Folwell 1996). A hot-water immersion system, on the other hand, can be easily assembled;
and is durable, mobile, and inexpensive (Sharp 1989). While hot water immersion is inherently more efficient than
vapor heat as a heat transfer medium and hot water treatment systems can be assembled for less than $8,000 (Sharp
1989, Kara et al. 1994), it can damage some fruits and vegetables. Hot water immersion is the only approved
quarantine treatment for mangos. More than 75 commercial hot water treatment faculties are in place in Mexico,
Haiti, Puerto Rico, South America, and Florida. The cost for each facility averages about $200,000. Additional
facilities are planned or being constructed. APHIS/PPQ must certify each facility and ensure that inspectors are on
site.
Alternatively, vapor heat and forced hot-air treatment systems are less damaging to commodities and more
versatile than other treatment systems, however they are more expensive. For example, both vapor heat and hot-air
treatment systems may initially require larger capital investments ranging from $20,000 to $200,000 for large
commercial facilities (Williamson 1996, Sharp 1994, Kara et al. 1994).
A comparison of the capital and operating costs of these technologies is provided in Table 1. Capital costs
for both vapor/forced air heat and methyl bromide treatments were calculated by dividing the costs to setup
commercial treatment systems (see above) by the tonnes of fruit treated over the 20 year lifetime of the facilities at
full capacity (i.e., capacities of 45,372 tonnes/yr. and 275,862 tonnes/yr. for forced air/vapor (for apples) and methyl
bromide treatment systems respectively). It was also assumed that treatment systems were operational 250 days of
the year and mat three forced air/vapor, and one methyl bromide treatment could be completed each day. Operating
costs included labor, energy, maintenance, insurance, and chemical costs in the case of methyl bromide.
As shown in Table 1, the capital costs for heat treatments are only slightly higher than that for methyl
bromide on a per tonne commodity basis. Operating costs for heat treatments, on the other hand, are eight times
higher than those for methyl bromide attributable primarily to longer treatment times and high energy costs. It is
likely, however, that operating costs will decrease in the future as the number of commercial heat treatment facilities
increases. Although the total costs for perishable commodity treatments with heat are seven times greater than that
with methyl bromide on a per tonne commodity basis, the relative proportion of this cost is small when compared to
the value of the commodity. Furthermore, other related costs (i.e., harvesting, packaging, storage, processing, and
transportation costs to bring the commodity to market) further reduce the percent contribution of heat treatments,
-------
making it a relatively insignificant cost overall. As a result, heat treatment can be a viable alternative to methyl
bromide for commodity treatment. In fact, Hawaii and many tropical countries have been using heat treatments as an
alternative to commodity fumigation for decades (Williamson 1996).
Table 1. Capital and Operating Cost Comparison
€est Faster. -:-"- """
r« - ~ \
""^ ^ *"
Capital Costs
Operating Costs
TOTAL
••. f
Ł&*&$»* $.
Forced Air/V'ajtfif fifeat
' <&*C»»ae][ *
4.41
25.00
29.41
'fr«aftaeBit#fc
MetMfarouiid*
l$$®a*& ;
1.33
3.04
4.37
Sources: Folwell 1996, Williamson 1996, Sharp 1989, Hara et al. 1994, Sharp 1994.
References
APHIS. 1993. Plant Protection and Quarantine Treatment Manual. United States Department of Agriculture.
Animal and Plant Health Inspection Service.
Armstrong JW. 1982. Development of a hot-water immersion quarantine treatment for Hawaiian grown 'Brazilian'
bananas. J. Econ. Entomol. 75:787-790.
Armstrong JW, Hansen JD, Hu BK, and Brown SA. 1989. High-temperature, forced-air quarantine treatment for
papayas infested with Tephritid fruit flies (Diptera: Tephritidae). J. Econ. Entomol. 82(6): 1667-1674.
Baker, A.C. 1939. The basis for treatment of products where fruit flies are involved as a condition for entry into the
United States. USD A Circular 551.
CoueyHM. 1989. Heat treatment for control of postharvest diseases and insect pests of fruits. Hort Science Vol.
24(2): 198-202.
Couey HM and Hayes CF. 1986. A quarantine system for Hawaiian papaya using fruit selection and a two-stage
hot-water treatment. J. Econ. Entomol. 79:1307-1314.
Folwell R. 1996 (August). Personal communication. Raymond Folwell. Department of Agricultural Economics,
Washington State University. Pullman, Washington.
Gaffhey JJ and Armstrong JW. 1990. High-temperature forced air research facility for heating fruits for insect
quarantine treatments. J. Econ. Entomol. 83(5): 1959-1964.
Gould WP. 1988. A hot water/cold storage quarantine treatment for grapefruit infested with the Caribbean fruit fly.
Proc. Fla. State Hort Soc. 101:190-192.
Gould WP and Sharp JL. 1992. Hot-water immersion quarantine treatment for guavas infested with Caribbean fruit
fly (Diptera: Tephritidae). J. Econ. Entomol. 85(4): 1235-1239.
Hallman GJ. 1989. Quality of Carambolas subjected to hot water immersion quarantine treatment. Proc. Fla. State
Hort. Soc. 102:155-156.
-------
Haliman GJ. 1990. Vapor-heat treatment of carambolas infested with Caribbean fruit fly (Diptera:Tephritidae). J.
Econ. Entomol. 83(6):2340-2342.
Haliman GJ. 1991. Quality of carambolas subjected to postharvest hot-water immersion and vapor heat treatments.
HortScience 26(2):286-287.
Haliman GJ and Sharp JL. 1990. Mortality of Caribbean fruit fly (Diptera: Tephritidae) larvae infesting mangoes
subjected to hot-water treatment, then immersion cooling. J. Econ. Entomol. 83(6): 2320-2323.
Haliman GJ and Sharp LJ. 1990a. Hot-water immersion quarantine treatment for carambolas infested with
Caribbean fruit fly (Diptera: Tephritidae). J. Econ. Entomol. 83(4): 1471-1474.
Haliman GJ, Gaffhey JJ, and Sharp JL. 1990. Vapor heat treatment for grapefruit infested with Caribbean fruit fly
(Diptera: Tephritidae). J. Econ. Entomol. 83(4): 1475-1478.
Hansen JD, Kara AH, and Tenbrink VL. 1992. Vapor heat: a potential treatment to disinfest tropical cut flowers
and foliage. HortScience 27(2): 139-143.
Kara A, Tsang M, Hata T, et al. 1994. Postharvest treatment alternatives for flowers and foliage. In: Annual
International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. November 13-16,
1994, pp. 74-1-74-2.
Kerbel EL, Mitchell FG, and Mayer G. 1987. Effect of postharvest heat treatments for insect control on the quality
and market life of avocados. HortScience 22(l):92-94.
Lay-Yee M. 1994. Responses of fruit to high temperature disinfestation. hi: Annual International Research
Conference on Methyl Bromide Alternatives and Emissions Reductions. November 13-16, 1994, pp. 66-1.
Mangan RL and Ingle SJ. 1992. Forced hot-air quarantine treatment for mangoes infested with West Indian fruit fly
(Diptera: Tephritidae). J. Econ. Entomol. 85(5): 1859-1864.
McGuire RG. 1991. Concomitant decay reductions when mangoes are treated with heat to control infestations of
Caribbean fruit flies. Plant Disease 75(9):946-949.
McGuire RG. 1991a. Market quality of grapefruit after heat quarantine treatment. HortScience 26(11): 1393-1394.
Mitcham EJ, L Neven, and B Biasi. 1994. Can sweet cherry take the heat ? In: Annual International Research
Conference on Methyl Bromide Alternatives and Emissions Reductions. November 13-16, 1994, pp. 68-1-68-2.
Miller WR, McDonald RE, Haliman GH, and Sharp JL. 1991. Condition of Florida grapefruit after exposure to
vapor heat quarantine treatment. HortScience 26(l):42-44.
Neven, L.G. and EJ. Mitcham. 1996. CATTS (controlled atmosphere/temperature treatment system): a novel tool
for the development of quarantine systems. American Entomologist spring 1996:56-59.
Sharp JL. 1985. Submersion of Florida grapefruit in heated water to kill stages of Caribbean fruit fly, Anastrepha
suspensa. Proc. Fla. State Hort. Soc. 98:78-80.
Sharp JL. 1986. Hot-water treatment for control of Anastrepha suspens (Diptera: Tephritidae). J. Econ. Entomol.
79:706-708.
Sharp JL. 1988. Status of hot water immersion quarantine treatment for Tephritidae immatures in mangos. Proc.
Fla. Stat Hort. Soc. 101:195-197.
Sharp JL. 1989. Hot-water immersion appliance for quarantine research. J. Econ. Entomol. 82(1): 189-192.
Sharp JL. 1989a. Preliminary investigation using hot air to disinfest grapefruit of Caribbean fruit fly immatures.
-------
Proc. Fla. State Hort. Soc. 102:157-159.
Sharp JL. 1990. Immersion in heated water as quarantine treatment for California stone fruits infested with
Caribbean fruit fly (Diptera: Tephritidae). J. Econ. Entomol. 83(4): 1468-1470.
Sharp JL. 1992. Hot-air quarantine treatment for mango infested with Caribbean fruit fly (Diptera:Tephritidae). J.
Econ. Entomol. 85(6):2302-2304.
Sharp JL. 1994. Hot-air-alternative quarantine treatment for methyl bromide fumigation to disinfest fruits. In:
Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. November
13-16, 1994, pp. 65-1-65-6.
Sharp JL and Gould WP. 1994. Control of Caribbean fruit fly (Diptera: Tephritidae) in grapefruit by forced hot air
and hydrocooling. J. Econ. Entomol. 87(1):131-133.
Sharp JL and Hallman GJ. 1992. Hot-air treatment for carambolas infested with Caribbean fruit fly (Diptera:
Tephritidae). J. Econ. Entomol. 85(1):168-171.
Sharp JL and Picho-Martinez H. 1990. Hot-water quarantine treatment to control fruit flies in mangoes imported
into the United States from Peru. J. Econ. Entomol. 83(5): 1940-1943.
Sharp JL and R.G McGuire. 1996. Control of Caribbean fruit fly (Diptera: Tephritadae) in navel orange by forced
air. J. Econ. Entomol. 89:in press.
Sharp JL and Spalding DH. 1984. Hot water as a quarantine treatment for Florida mangos infested with Caribbean
fruit fly. Proc. Fla. State Hort. Soc. 97:355-357.
Sharp JL, Ouye MT, Thalman R, et al. 1988. Submersion of 'Francis1 mango in hot water as a quarantine treatment
for the West Indian fruit fly and the Caribbean fruit fly (Diptera: Tephritidae). J. Econ. Entomol. 81(5): 1431-1436.
Sharp JL, Ouye MT, Hart W, Ingle S, et al. 1989. Immersion of Florida mangos in hot water as a quarantine
treatment for Caribbean fruit fly (Diptera: Tephritidae). J. Econ. Entomol. 82(1): 186-188.
Sharp JL., Ouye MT, Ingle SJ and Hart WG. 1989a. Hot-water immersion quarantine treatment for mangoes from
Mexico infested with Mexican fruit fly and West Indian fruit fly (Diptera: Tephritidae). J. Econ. Entomol.
82(6):1657-1662.
Sharp JL, Ouye MT, Ingle SJ et al. 1989b. Hot-water quarantine treatment for mangoes from the State of Chiapas,
Mexico, infested with Mediterranean fruit fly and Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae). J.
Econ. Entomol. 82(6): 1663-1666.
Sharp JL, Gaffhey JJ, Moss JI, and Gould WP. 1991. Hot-air treatment device for quarantine research. J. Econ.
Entomol. 84(2):520-527.
Tsang, MMC, AH Kara, TY Hata, BKS Hu, RT Kaneko, and V. Tenbrink. 1995. Hot water immersion unit for
disinfection of tropical floral commodities. American Society of Agricultural Engineers. 11(3):397-402.
UNEP. 1992. Methyl Bromide: Its atmospheric science, technology, and economics. Montreal Protocol Assessment
Supplement. United Nations Environment Programme. June.
UNEP. 1994. Montreal Protocol on substances that deplete the ozone layer. United Nations Environment
Programme. 1994. Report of the Methyl Bromide Technical Options Committee. 1995 Assessment.
EPA 430/K94/029
Williamson, M. 1996 (August). Personal communication. Michael Williamson. University of Hawaii at Menoa.
Menoa, Hawaii.
-------
&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
December 1996
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Heat Treatments to Control Pests on Imported Timber
Exotic or introduced timber pests can have damaging effects on forest ecosystems or timber production areas.
North American forests are particularly vulnerable to pests such as fungi, nematodes, or insects introduced through
importation of logs, lumber, or unmanufactured wood articles (USDA, 1994a). Because trees produced in temperate
areas outside North America are affected by and can introduce a wide variety of pests and diseases that are non-
indigenous to this continent, special care is required to ensure that imported wood and wood products are pest-free. The
introduction of non-indigenous species could be detrimental to U.S. forest production, recreation, and urban forest
resources (USDA, 1991 a). Pests from tropical hardwoods, however, pose less of a threat, because tropical hardwood
pest habitat requirements cannot generally be met within the temperate forests of the United States (Thomas 1996).
These pests can bore into the roots, limbs, or trunk can interfere with a tree's reproductive capabilities, and can cause
defoliation, wood damage, or a shift in tree species composition over time. Extensive tree death can have serious
impacts on the ecosystem and cause changes in habitat and food supply. In addition, establishment of non-indigenous
organisms has clearly been shown to reduce biodiversity (USDA 1994a).
There are several historical examples showing
that importation of non-indigenous timber pest species has
led to wide-spread blights within the United States.
Notable cases this century have included: Chestnut blight
(Cryphonectria parasitica, 1904-1955), Dutch elm disease
(caused by the fungus Ophiostoma ulmi, mid-1920s),
White pine blister rust (fungus Cronartium ribicola, early
1900s), Port Oxford cedar root rot (fungus Phytophthora
lateralis, 1923), and the recent Gypsy moth (Lymantria
dispar, 1870s) outbreaks. Each of these outbreaks has
caused ecological damage such as shifts in species
composition, changes in habitat, as well as tree defoliation,
stress, and death (USDA, 1994a).
/
Benefits of Heat Treatment of
Logs and Lumber
Reduces or eliminates insect and fungal
pests
Increases value of wood products
Excellent penetration to wood core
Saves time, labor, and resources.
No chemical residues or environmental
contamination
Methyl Bromide May Not Effectively Control Pests on Imported Logs and Lumber
Currently, many U.S. timber importers rely on methyl bromide fumigation to control pests and pathogens such
as Lymantria dispar (Asian gypsy moth), Lachnellula willkommii (Larch canker), and Sirococcus strobilinus (Conifer
shoot blight) (USDA 1991 a p.6). While methyl bromide is used to fumigate timber and wood products, it may not be
the most effective treatment for controlling quarantine pests (e.g., bark beetles and borers, termites, and fungus) on
imported logs and lumber (USDA 1994a p. 31 and 19, USDA 1991 a p.5-6). Further, it is believed that methyl
bromide does not penetrate well into logs, particularly logs with a high moisture content. Cross (1992) found that it is
difficult to achieve useful insecticidal doses much beyond a depth of 100 millimeters in green materials using
conventional tent fumigation techniques. Likewise, according to the USDA, "there is little scientifically derived efficacy
data available to determine the most effective ways to employ methyl bromide fumigation to destroy plant pests
associated with imported wood products" (USDA 1994a, p. 31). Additionally, recent test shipments of wood products
imported into U.S. that were fumigated with methyl bromide have been found to be infested with fungal pests upon
-------
arrival (Forest Service, 1992 in USDA 1994a, p. 31 and Appendix B-81). Methyl bromide, therefore, when used to
treat logs and lumber, does not completely eradicate the risk of quarantine pests entering new territory.
USDA Risk Assessments
In 1990, the Department of Agriculture Animal and Plant Health Inspection Service (APHIS) received its first
request to import logs from the Soviet Union. At the time, the associated risks of importing timber, and the lack of
APHIS regulations led to concern over the long-term impact of importing foreign timber. Three months later, APHIS
turned down the request, and implemented a formal ban on all logs from the Soviet Union until further research could be
conducted (USDA 1994a, USDA 1990a). As a result, between 1991 and 1993, the USDA Forest Service conducted
three risk assessments on imported timber:
• Assessment of the Importation of Larch from Siberia and the Soviet Far East (1991) (USDA 1991b);
• Assessment of the Importation ofPinus radiata and Douglas Fir Logs from New Zealand (1992) (USDA
1992); and,
• Assessment of the Importation ofPinus radiata, Nothofagus dombeyi, and Lauretta phillippiana from Chile
(1993) (USDA 1993).
APHIS used these assessments to develop its extensive mitigation measures for minimizing pest introductions
in the U.S. during the importation of foreign logs and lumber. The proposed APHIS plan, which has been developed as
a result of the Forest Service risk assessments, would allow importers to choose between several pest treatment
strategies (APHIS would oversee decisions and evaluate all strategies on the basis of effectiveness). If a strategy cannot
be shown to produce negligible risk, then APHIS has the power to deny entry.
Heat Treatments are Considered a Viable Method to Control Quarantine Pests
Based on USDA risk assessments, heat treatments of logs and lumber are considered to be more effective than
methyl bromide for providing quarantine security and are considered to be an effective alternative to methyl bromide for
the control of quarantine pests (USDA 1996). As a result, the use of heat-based sterilization to control biological pests
offers great potential for the imported timber industry. Both moist heat (steam or hot water) and dry heat have been
shown to effectively control fungi, insects, and nematodes associated with logs and lumber products (USDA 1991 a)
(Task Force on Pasteurization of Softwood Lumber 1991, Jones 1973, Baker 1969, Snyder and St. George 1924)
(Dwinell 1990, USDA 1991; Ostaff and Cech 1978, Ostaff and Sheilds 1978, Parkin 1973, Department of Scientific
and Industrial Research, Great Britian 1957, Snyder and St. George 1924, Snyder 1923) .
To effectively eliminate pests, heat treatment requires that the internal temperature of the logs and lumber be
raised to a specified temperature over a given period of time. Regulations require that all heat treatments be performed
at a facility authorized by APHIS or by an inspector authorized by the national government of the country in which the
facility is located (USDA 1994a). Core temperatures can be monitored by using thermocouples. Heat treatment
techniques may include the use of steam, hot water, kilns (lumber only), microwave energy, or any other method that
raises the temperature at the center of the log to at a minimum of 71 ° C (167 °F) for at least 60 minutes.
Several treatment specifications are available for using steam or dry heat to treat logs and lumber. Typically,
pressurized steam can be introduced to a chamber, and dry heating (with moisture added to minimize warping and
spiking) can be accomplished using a commercial kiln. Because the killing efficacy of heat treatments depends on the
time, temperature, and humidity (USDA 1991a p. 17), steam heat will kill pests more efficiently and rapidly than dry
heat because the organisms under moist conditions are more susceptible to thermal killing due to the denaturation of
proteins, particularly enzymes (USDA 1994a p. 3, USDA 1991, USDA 1990a ). However, despite the effectiveness of
steam heat treatments, kiln drying is the most commonly used heat treatment for lumber (Mathews 1996, Griffin 1996,
Waggener 1996, Briggs 1996, Morrell 1996, Loromer 1996). The specifications for moisture-reduced heat treatment
are the same as those for standard heat treatment, with the added component that moisture must be reduced to 20 percent
or less. Penetration of dry heat proceeds at a much slower rate than steam heat, therefore kiln drying requires a much
longer exposure time (USDA 1994a).
-------
As is the case wifli methyl bromide, heat treatment has been found to be effective for killing insects and plant
pathogens on and within the regulated article only at the time of treatment (i.e., with no residual protective effect),
articles must be protected against subsequent reinfestation. A wide variety of methods, separate or in combination, may
be used to control reinfestation, including storage in pest-free warehouses, storage in sealed containers, or the use of
prophylactic pesticide sprays or dips (USDA 1994a). Kiln drying, stream heating, and hot water immersion can
eliminate deep wood pests and can also make the regulated article less vulnerable to reinfestation.
Heat Treatment: Effects on Wood QuaUty
Both steam and dry heat can effectively penetrate logs and raise the internal temperatures to levels that
effectively control pests without causing wood damage (USDA 1991 a), hi general, heat treatments do not have any
significant deleterious effects on log quality because controlled heat treatments help to reduce wood damage caused by
uneven drying (USDA, 1994). Temperatures up to 82.2 °C (180 °F) for periods up to one hour do not appreciably
affect the properties of wood (USDA 1994a). Depending upon the type of wood and size, some surface damage may be
noted. Potential damage to lumber caused by poor drying includes the following: surface checks, warping, uneven
moisture content, and discoloration (USDA 1991c). Additional research is needed to determine more clearly the
potential deleterious effects of heat treatment on logs and other wood articles (USDA 1994a ).
Additionally, the value of wood is often increased by proper heat treatment. Whereas green wood products
treated with methyl bromide do not incur any additional value, heat treatments cure the wood and impart value compared
to unseasoned or untreated wood. For example, wood that has been milled and heat treated (i.e., kiln dried or steam
treated) typically has 30-50 percent greater value than untreated wood (Rice 1996, McDonagh 1996). Because wood
treated with methyl bromide must be dried and cured via heat treatment anyway and because heat treatments provide
similar pest control benefits compared to methyl bromide, methyl bromide treatments may be superfluous. However,
some users prefer to purchase "green wood", re-manufacture the material, then dry it.
Costs
A comparison of the costs of sterilizing logs and lumber with methyl bromide fumigation vs. heat treatment
(i.e., kiln-drying and steam treatments) is provided in the Table 1. As shown, the net costs for both kiln-drying and
steam treatments are negative because of the increased product value resulting from the heat treatment process.
However, it must again be noted that some types of timber and wood products may be damaged by heat treatments, and
thus would change the cost listed here. The costs for methyl bromide fumigation include labor, tarp, and chemical costs.
The costs for heat treating and steam treating lumber include labor, energy, and equipment costs. The labor and energy
costs for both kiln-drying and steam treatments, however, vary according to treatment time. Heat treatment can take up
to 25 days, whereas steam treatment takes only 1 -2 days. Furthermore, steam heating is less labor intensive than kiln
drying. Kiln drying requires that "sticks" (or pieces of wood) be inserted between layers of wood to allow better
distribution of heat and air flow during the treatment process, however, these sticks must be removed before shipping.
However, many mills now have automatic stackers which markedly reduce labor costs. In steam drying, a lath (or a thin
piece of residual wood) is used to separate the layers, and does not need to be removed before shipping. Another factor
contributing to the cost discrepancy between kiln-dried vs. steam treated wood is Btu utilization. For dry heat
sterilization, low heat (low Btu) is used initially, but then gradually increased until the maximum heat (high Btu) is
obtained on the 25th to 26th day (for hardwoods -- conifers are normally dried for 3-5 days). For steam sterilization,
however, the same amount of heat used in the final stage of kiln drying is used at the beginning of the process and is
sustained by small bursts of heat throughout the short 1 or 2 day treatment process. Furthermore, the chamber vents are
kept closed to aid in heat conservation. Therefore, steam sterilization takes both less time and utilizes less heat energy
compared to that used in dry heat sterilization, ultimately reducing energy costs.
-------
Table 1. Timber Treatment Cost Comparison
Cost Considerations
Product Initial
Cost/Value
(Pre-Treatment)
Treatment Cost
Total Cost
Value Added
Product Value
(Post Treatment)
Net Cost
Methyl Bromide
500-850
1-3
501-853
N/A
500-853
1-3
Heat Treatment
Softwood Hardwood
(e.g., Ftr) (e.g., Oak/
500
85-155"
585-655
850
100-200"
950-1050
30-50%
655
5-(65)
1275
(225-325)
SteaM treatment
Softwood Hardwood
(e,g.>Fir) (e.g.> Oak/
500
35-60
535-560
850
41-77
891-927
30-50%
650
(90-115)
1275
(348-384)
N/A - not applicable.
( ) - indicates a negative net cost attributed to increased product value
* Cost refers to kiln treatment of softwood species indigenous to the western U.S. (e.g., Cedar, Douglas Fir).
b Treatment cost and value added refers to kiln treatment of hardwood species indigenous to the eastern U.S. (e.g., Oak,
Cherry).
Sources: Rice 1996, USDA 1996, Mathews 1996, Milota 1996, McDonagh 1996, McGehee 1996, UNEP 1995.
References:
Baker, K.F. 1969. Aerated-steam Treatment of Seed for Disease Control. Horticultural Research. Volume 9.
Pages 59-73.
Briggs. 1996 (July 16). Personal communication. David Briggs, Professor, University of Washington. Seattle,
Washington.
Chidester, M.S. 1937. Temperatures Necessary to Kill Fungi in Wood. Proceedings from the American Wood
Preservers Association. Volume 33. Pages 316-324.
Chidester, M.S. 1939. Further Studies on Temperature Necessary to Kill Fungi in Wood. Proceedings from the
American Wood Preservers Association. Volume 35. Pages 319-324.
Cross, D.J. 1992. Penetration of Methyl Bromide in Pinus radiata Wood and Its Significance for Export
Quarantine. New Zealand Journal of Forest Science. Volume 21. Number 2 and 3. Pages 235-245.
Department of Scientific and Industrial Research, Great Britian, 1957. The Kiln Sterilization of Lycfttf-infested
Timber. Leafl.13. Princes Risborough, UK: Forest Products Research Laboratory. Page 4.
Dwinell, L.D. 1990. Heat-treating and Drying Southern Pine Lumber Infested with Pinewood Nematodes. Forest
Products Journal. Volume 40. Number 11/12. Pages 53-56.
-------
EPA. 1986. Guidance for Registration of Pesticide Products Containing Methyl Bromide as the Active Ingredient.
United States Environmental Protection Agency, Office of Pollution and Toxic Substances. Washington, DC.
Griffin. 1996 (July 17). Personal communication. Robert Griffin, United States Department of Agriculture, Animal
and Plant Health Inspection Service. Hyattsville, MD.
Jones, T.W. 1973. Killing the Oak Wilt Fungus in Logs. Forest Products Journal. Volume 23. Pages 52-54.
Loromer. 1996 (July 17). Personal Communication. Jennifer Loromer. United States Department of Agriculture,
United States Forest Service. Washington, DC.
Matthews. 1996 (July 17). Personal Communication. Jim Matthews, Western Wood Products Association.
Portland, Oregon.
McDonagh. 1996 (September 3). Personal Communication. Tom McDonagh, Rex Lumber Company. Acton,
Massachusetts.
McGehee. 1996 (September 9,11,13, 17). Personal Communication. Stan McGehee, Willamette Industries, me.
Sweethome, Oregon.
McLean, J.D., 1952. Preservative treatment of wood by pressure methods. U.S.D.A. Agricultural Handbook 40.
Washington, DC.
Milota. 1996 (July 17). Personal Communication. Mike Milota, Oregon State University. Corvallis, Oregon.
Morrell. 1996 (July 16). Personal communication. Jeff Morrell, Professor, Department of Forest Products, Oregon
State University. Portland, Oregon.
Newbill, M.A. and J.J. Morrell. 1991. Effects of Elevated Temperatures on the Survival On Basidiomycetes that
Colonize Untreated Douglas-fir Poles. Forest Products Journal. Volume 41. Number 6. Pages 31-33.
Rice. 1996 (July 18). Personal Communication. Bob Rice, University of Maine at Orno. Orno, Maine.
Sahle-Demessie, E., K.L. Levien, J.J. Morrell, and M.A. Newbill. 1992. Modeling internal temperature changes of
timber poles during ACA treatment. Wood Science and Technology 26:227-240.
Snyder, T.E. 1923. High Temperatures as a Remedy for Lyctus Power-post Beetles. Journal of Forestry. Volume
21. Pages 810-814.
Snyder, T.E. and R.A. St. George. 1924. Determination of Temperature Fatal to the Powderpost Beetle, Lyctus
planicollis LeConte, Steaming Infested Ash and Oak Lumber in a Kiln. Journal of Agricultural Research. Volume
28. Number 10. Pages 1033-1038.
Task Force on pasteurization in Softwood Lumber. 1991. The Use of Heat Treatment in the Eradication of the
Pinewood Nematode and Its Vectors in Softwood Lumber.
Thomas. 1996 (July 17). Personal communication. Don Thomas, United States Department of Agriculture, Animal
and Plant Health Inspection Service. Washington, DC.
Ostaff, D.P. and M.Y. Cech. 1978. Heat-sterilizaion of Spruce-pine-fir Lumber Containing Sawyer Beetle Larve
(Coleoptera: Cerambycidae), Monochamus sp. Rep. OPX200E. Ottawa, ON: Canada Forestry Service. Page 9.
Ostaff, D.P. and J.K. Sheilds. 1978. Reduction of Loses to Logs and Lumber Caused by Wood-boring insects.
Rep. OPX218E. Ottawa, ON: Canada Forestry Service. Page 15.
-------
Parkin, E.A. 1973. The Kiln-sterilization of timber infested by Lyctus powder-post battles. Journal of Forestry.
Volume 11. Pages 32-39.
USDA., 1991a. An Efficacy Review of Control Measures for Potential Pests of Imported Soviet Timber. USDA,
Animal and Plant Health Inspection Service. Miscellaneous Publication No. 1496. September 1991.
USDA. 1991b. Pest Risk Assessment of the Importation of Larch from Siberia and the Soviet Far East. USDA,
Forest Service. Miscellaneous Publication No. 1495. September 1991.
USDA. 1991c. Dry Kiln Operator's Manual. USDA, Forest Service, Forest Products Laboratory. Madison,
Wisconsin. Agricultural Handbook No. 188. August 1991.
USDA. 1992. Pest Risk Assessment of the Importation of Pinus radiata and Douglas-fir Logs from New Zealand.
USDA, Forest Service. Miscellaneous Publication No. 1508. October 1992.
USDA. 1993. Pest Risk Assessment of the Importation of Pinus radiata, Nothofagus dombeyi, and Laurelia
philippiana Logs from Chile. USDA, Forest Service. Miscellaneous Publication No. 1517.
USDA. 1994a. Importation of Logs, Lumber, and Other Unmanufactured Wood Articles: Environmental Impact
Statement.
USDA. 1994b. Proposed Rules: Importation of Logs, Lumber, and Other Unmanufactured Wood Articles. USDA,
Animal and Plant Health Inspection Service. 7 CFR Part 319 [Docket No. 91-07403]. RIN 0579-AA47.
USDA. 1996. Importation of Logs, Lumber, and Other Unmanufactured Wood Articles. 7CFR319.40. United
States Department of Agriculture, Animal and Plant Health Inspection Service (APHIS). Washington, DC.
UNEP. 1995. Montreal Protocol on Substances that Deplete the Ozone Layer, 1994 Report of the Methyl Bromide
Technical Options Committee: 1995 Assessment. United Nations Environment Programme, Ozone Secretariat.
Nairobi, Kenya.
Waggener. 1996 (July 16). Personal communication. Thomas Waggener, Professor, University of Washington.
Seattle, Washington.
-------
&EPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
December 1996
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
The Use of Irradiation for Post-Harvest and Quarantine Commodity Control
In both domestic and international agricultural markets, expanding the use of irradiation can help to reduce
the need for methyl bromide for the post-harvest control of insect pests. Currently, irradiation treatments have been
approved for a variety of food use applications by the U.S. Food and Drug Administration (FDA). The United States
Department of Agriculture (USD A)/Animal and Plant Health Inspection Service (APHIS)/Plant Protection and
Quarantine Service (PPQ) has outlined policy positions regarding the development and use of irradiation treatments
for quarantine pest control, and is actively seeking ways to incorporate additional irradiation uses into their plant
protection program (USDA 1995, USDA 1996a, 1996b, 1996c). Furthermore, research has been conducted to
determine optimal irradiation dosages for controlling pests and maintaining produce quality, a variety of irradiation
technologies have been commercialized worldwide, and there is extensive data available on the capital, operating, and
per unit treatment costs associated with irradiation projects. In addition, recent market studies have generally found
that consumers are willing to buy irradiated produce (Morrison 1992). In fact, research conducted in Florida indicated
that consumer acceptance for such commodities is high, and many actually prefer the methods to traditional chemical
fumigation (Marcotte 1992).
Food irradiation is a process by which
products are exposed to ionizing radiation to sterilize
or kill insects and microbial pests by damaging their
DNA. The FDA permits three types of ionizing
radiation to be used on foods: gamma rays from
radioactive cobalt-60, high energy electrons, and x--
rays. Although all three have similar effects, gamma
rays are most commonly used in food irradiation
because of their ability to deeply penetrate pallet
loads of food (Forsythe and Evangelou 1993,
Morrison 1989). Gamma irradiation equipment
irradiates packaged or bulk commodities by exposing
the product to gamma energy from cobalt-60 in
closed chambers, which range in size from single
•"
Benefits of Food Irradiation
Disinfests fruits, vegetables, and grains by
sterilizing or killing insects and microbial pests.
Insures the delivery of pest-free commodities to
importing nations resulting in increased trade
opportunities.
Reduces the risk of infection and disease.
Slows sprouting and ripening in some fresh fruits
and vegetables resulting in an extended shelf life.
modular pallet irradiators to large research or
contract irradiation facilities. Absorbed dose is measured as the quantity of radiation imparted per unit of mass of a
specified material. The unit of absorbed dose is the gray (Gy) where 1 gray is equivalent to 1 joule per kilogram
(ICGFI1991, NAPPO 1996).
Benefits of Irradiation
There are several benefits of expanding the use of irradiation treatments to control pests infesting perishable
and non-perishable commodities in the United States. First, irradiation may be useful for preventing the movement of
quarantine species possibly present in trade commodities into areas where such pests are not established (USDA
1996b). From an economic standpoint, irradiation, therefore, has the potential to increase trade opportunities between
nations, especially from major fruit and vegetable producing countries with high infestation rates (ICGFI 1994).
-------
Irradiation also can be used to reduce the risk of infection and disease caused by foodborne pathogens (Moy 1991).
Although consumers have concerns associated with the safety of irradiation technology and its effects on food,
research indicates that properly irradiated food does not pose a risk to consumers (Thorne 1983, OTA 1985). In fact,
the potential for human health impacts from exposure to foodborne pathogens is believed to be substantially reduced
through the use of irradiation (OTA 1985, Morrison et al. 1992).
In addition, by interfering with cell division, irradiation inhibits sprouting in tubers, bulbs, and root
vegetables (potatoes, onions) and can delay ripening of some tropical fruits, resulting in an extended shelf life for
many foods. In turn, longer shelf lives will enhance trade opportunities between nations by extending time constraints
under which fresh produce must be delivered to more distant geographic markets or by allowing the use of slower and
less expensive modes of transportation (Kader 1986, Moy 1991, OTA 1985).
Uses of Irradiation
Irradiation is used as a pest control tool in over 40 countries, including the United States, Russia, Great Britian
and Brazil (Nordion 1995). The disinfestation of grain as it enters the Soviet Union at the Black Sea Port of Odessa,
estimated at over 500,000 metric tons per year, is one of the largest documented commercial industrial applications
(Giddings 1991). In the United States, the FDA approved low-doses irradiation for wheat, wheat flour, and potatoes
in the early 1960s. In 1984 and 1985, the FDA approved irradiation of spices and pork, and in the following year,
approved low-dose irradiation (up to 1 kGy) to control insects in foods and extend the shelf life of fresh fruits and
vegetables (Kader 1986, Morrison 1989). Irradiation has also been used to sterilize food for U.S. hospital patients
and astronauts (Morrison 1992). Further, irradiation disinfestation has been found to be effective for treatment of
dried fruits, spices, nuts, cut flowers, lumber, and wood chips (ICGFI1994, Marcotte 1992, Morrison 1989, OTA
1985). At doses below 1 kGy, irradiation is an effective treatment against various species of fruit flies, mango seed
weevils, naval orange worms, potato tuber moths, codling moths, and other insect species of significance to
quarantine situations (Kader 1986). For irradiation to be approved as a quarantine treatment in the United States,
either as a single treatment, or as part of a combined approach (e.g., systems approach), USDA/APHIS/PPQ will
require that the level of efficacy be scientifically demonstrated, and that efficacy be demonstrated under commercial
settings (USDA 1996b).
Effective Dosages and Impact on Produce Quality
Because foods differ in their radiation dose requirements, densities, as well as specific packing
configurations (Kunstadt et al. 1990), research has focused on insect mortality, morbidity, and sterilization, as well as
the effects of ionizing radiation on fruit quality. The effects of irradiation depend on the dose absorbed. Low doses (up
to 1 kGy) inhibit sprouting in tuber, bulb and root vegetables, inhibit the growth of asparagus and mushrooms, and delay
physiological processes (ripening, etc.) in such fruits as banana, mango, and papaya. Medium doses (1 to 10 kGy)
extend the shelf life of commodities, eliminate spoilage and pathogenic microorganisms, and improve the technical
properties of food. Lastly, high doses (10 to 50 kGy) can be used for industrial sterilization and decontamination of
certain additives or ingredients (Morrison 1992, ICGFI 1994, OTA 1985, Kader 1986).
In 1984, the International Consultive Group on Food Irradiation (ICGFI) convened in Washington, D.C., to
develop a set of guidelines for the irradiation of fresh produce. The group established minimum doses that could provide
effective treatments against most arthropod pests (ICGFI 1994). Doses used to disinfest foods and agricultural
products are usually between 0.15 kGy (minimum dose for fruit fly sterilization and to prevent larval development)
and 0.30 kGy (to control other species of insects and mites), but may go as high as 1 kGy (Forsythe and Evangelou
1993, Marcotte 1992). While research has proven irradiation to be effective at sterilizing pest insects, there is concern
as to how quarantine inspectors would tell the difference between sterile and non-sterile insects that physically appear
the same.
-------
Unless already established, the correct dose required for a specific commodity infested with a specific pest
must be determined through testing. Results of some of the studies that have investigated dose requirements include:
• Research on the mango seed weevil in the U.S. has shown that irradiation at doses of 0.30 kGy
prevented adult emergence from infested fruit (ICGFI ,1994).
• USDA researchers in Florida found that radiation doses as low as 0.30 kGy were effective in
eliminating plum curculio (Conotrachelus nenuphar), and blueberry maggot (Rhagoletis mendax),
without altering overall fruit quality (Hallman and Miller 1994).
« Researchers at Washington State University conducted a series of tests on 'Rainier' cherries and
determined that irradiation levels as high as 0.30 kGy had no effect on composition, color, of taste.
They also concluded that doses of 0.15 and 0.25 kGy were effective in controlling cherry fruit flies
and codling moths, respectively (Drake et al. 1994).
• Studies done at me U.S. Horticultural Research Laboratory in Florida (USDA/ARS, Orlando)
showed that irradiation doses up to 0.75 kGy were sufficient in controlling apple maggot
(Rhagoletis pomonella), blueberry maggot (Rhagoletis mendax), and plum curculio (Conotrachelus
nenuphar), without doing any damage to the fruit's composition or taste (Miller and McDonald
1994).
Factors influencing the response of fresh fruits and vegetables to irradiation include the type of commodity
and cultivar, production area and season, maturity at harvest, initial quality, and post harvest handling procedures.
Similarly, environmental conditions during irradiation (temperature and atmospheric composition), and dose rates are
also influencing factors (ICGFI 1994, Kader 1986, OTA 1985, Morrison 1992). The relative tolerances of fresh
fruits and vegetables to irradiation doses below 1 kGy are listed in Table 1 below.
Table 1. Relative Tolerance of Fresh Fruits and Vegetables to Irradiation below 1 kGy
High
Medium
Low
Apple, cherry, date, guava, longan, muskmelon, nectarine,
raspberry, strawberry, tamarillo, tomato
papaya,
peach, rumbutan,
Apricot, banana, cherimoya, fig, grapefruit, kumquat, loquat, lychee, orange, passion
fruit, pear, pineapple, plum, tangelo, tangerine
Avocado, cucumber, grape, green bean, lemon, lime, olive
summer squash, leafy vegetables, broccoli, cauliflower
, pepper
, sapodilla, soursop,
Source: Kader 1986.
Costs
The actual cost of food irradiation is influenced by dose requirements, the food's tolerance of radiation,
handling conditions (i.e., packaging and stacking requirements), construction costs, financing arrangements, and other
variables particular to the situation (Forsyte and Evangel 1993, USDA 1989). Irradiation is a capital-intensive
technology requiring a substantial initial investment, ranging from $1 million to $3 million (or possibly more for
special applications). In the case of large research or contract irradiation faculties, major capital costs include a
radiation source (cobalt-60), hardware (irradiator, totes and conveyors, control systems, and other auxiliary
equipment), land (1 to 1.5 acres), radiation shield, and warehouse. Operating costs include salaries (for fixed and
variable labor), utilities, maintenance, taxes/insurance, cobalt-60 replenishment, general utilities, and miscellaneous
operating costs (Kunstadt et al., USDA 1989).
-------
Based on a review of public information on the costs of treating a variety of food items with irradiation,
Table 2 presents data on the per-unit costs for gamma irradiation and methyl bromide treatments for selected crops.
Although irradiation is more expensive than fumigating with methyl bromide, the cost of irradiation may be offset by
its many benefits, including reduced damage to fruits and vegetables and an extended shelf life. Furthermore, it is
likely that irradiation costs will decrease in the future as the number of commercial irradiators and volumes of treated
commodities increases, hi addition, the relative proportion of the treatment cost is small when compared to the value
of the commodity. Furthermore, other related costs (i.e., harvesting, packaging, storage, processing, and
transportation costs to bring the commodity to market) further reduce the percent contribution of irradiation
treatments, making it a relatively insignificant cost overall.
Table 2. Comparison of Estimated Post-Harvest Treatment Costs
for Selected Crops.
Strawberries
Papaya
Mango
0.88 to 0.94
2.5 to 8.1
0.9 to 4.2
N/A
N/A = Data not available.
Sources: Forsythe andEvalgelou 1993 and 1994, Morrison 1989.
References
Drake et al. 1994. Effects of Low Dose Irradiation on Quality of 'Rainer' Cherries. Proceedings from the 1994
International Conference on Methyl Bromide Alternatives and Emissions Reductions. Kissimmee, PL
Forsythe and Evangelou. 1993. Costs and Benefits of Irradiation and Other Selected Quarantine Treatments for Fruit
and Vegetable Imports to the United States of America. Issue Paper. Proceedings of An International Symposium on
Cost-Benefit Aspects of Food Irradiation Processing Jointly Organized by the International Atomic Energy Agency,
The Food and Agricultural Organization of the United Nations, and the World Health Organization. Aix-En-
Provence, Vienna. March 1-5, 1993.
Forsythe and Evangelou. 1994. Costs and Benefits of Irradiation versus methyl bromide fumigation for disinfestation
of U.S. fruit and vegetable imports. U.S. Department of Agriculture, Economic Research Service, Agriculture and
Trade Analysis Division, Washington, D.C., March 1994.
Giddings. 1991. Radiation Disinfestation of Agricultural Commodities. Nordion International, Inc. Kanata, Ontario,
Canada.
Hallman and Miller. 1994. Irradiation as an Alternative to Meuiyl Bromide Quarantine Treatment for Plum Curculio
in Blueberries. Proceedings from the 1994 International Conference on Methyl Bromide Alternatives and Emissions
Reductions. Kissimmee, FL.
ICGFI. 1991. Facts About Food Irradiation. International Consultative Group on Food Irradiation, Fact Sheet
Series, May 1991.
ICGFI. 1994. Irradiation as a Quarantine Treatment of Fresh Fruits and Vegetables. A report of the Working
Group Convened by ICGFI, U.S. Department of Agriculture, Washington, D.C., March 22 to 25, 1994.
-------
Kader 1986. Potential Applications of Ionizing Radiation in Postnarvest Handling of Fresh Fruits and Vegetables.
Food Technology, Volume 40, Number 6, June, 1986, pp. 117-121.
Kunstadt et al. 1990. Economics of Food Irradiation. P. Kunstadt, C. Steeves, D. Scaulieu, Nordion Technical
Paper. Market Development, Food Irradiation Division, Nordion International Inc. Kanata, Ontario, Canada.
Marcotte. 1992. The Practical Application of Irradiation Disinfestation for Food and Agricultural Commodities.
Proceedings from the 7992 International CFC and Halon Alternatives Conference, Washington, D.C. September
1992.
Miller and McDonald. 1994. Irradiation as an Alternative Quarantine Treatment to Methyl Bromide for Blueberries.
Proceedings from the 1994 International Conference on Methyl Bromide Alternatives and Emissions Reductions.
Kissimmee, FL
Morrison. 1989. An Economic Analysis of Electron Accelerators and Cobalt-60 for Irradiating Food. Rosanna
Mentzer Morrison. U.S. Department of Agriculture, Economic Research Service, Technical Bulletin #1762, June,
1989.
Morrison. 1992. Food Irradiation Still Faces Hurdles. Food Review. October-December, pp. 11-15.
Morrison et. al. 1992. Irradiation of U.S. Poultry -Benefits, Costs, and Export Potential. Food Review. October-
December, 1992, pp. 16-21.
Moy. 1991. Plant Quarantine Treatment by Irradiation: Potential Benefits and Barriers in International Trade.
Proceedings from the International Plant Quarantine Congress. Kuala Lumpur, Malaysia.
NAPPO. 1996. NAPPO Standards for Phytosanitary Measures. Guidelines for the Use of Irradiation as a
Phytosanitary Treatment. Draft for the Secretariat of the North American Plant Protection Organization, Nepean,
Ontario, Canada, July 1, 1996.
Nordion. 1995. World Suppliers of Contract Gamma Processing Services -1995. Nordion International, Inc.,
Kanata, Ontario, Canada.
OTA. 1985. Food Irradiation: New Perspectives on a Controversial Technology. Rosanna Mentzer Morrison and
Tanya Roberts, Office of Technology Assessment, Congress of the United States, Washington, DC. December 1985.
Thorne. 1983. Developments in Food Preservation. Applied Science Publishers Ltd., S. Thome, ed., Essex,
England. Chapter 2.
USD A. 1995. The application of irradiation to Phytosanitary problems. Position Discussion Document IV, U.S.
Department of Agriculture, Animal Plant Health Inspection Service, Plant Protection and Quarantine, Washington,
D.C., September 1995.
USDA. 1996a. Papaya, Carambola, and Litchi from Hawaii. Federal Register, U.S. Department of Agriculture,
Animal Plant Health Inspection Service, Washington, D.C., Volume 61, No. 142, pp. 38108 - 38114.
USDA. 1996b. The application of irradiation to phytosanitary problems. Federal Register, U.S. Department of
Agriculture, Animal Plant Health Inspection Service, Washington, D.C., Volume 61, No. 95, pp. 24433 - 24439.
USDA. 1996c. Methyl bromide alternatives newsletter. U.S. Department of Agriculture, Washington, D.C.,
January, 1996.
-------
-------
vxEPA
United States
Environmental
Protection Agency
Office of Air and Radiation
(6205-J)
December 1336
Stratospheric Ozone Protection
Case Study
Methyl Bromide Alternative
Structural Fumigation Using Sulfuryl Fluoride: DowEIanco's Vikane™ Gas Fumigant
Sulfuryl fluoride (SO2F2), also known as Vikane™ (99.8 percent by weight sulfuryl fluoride and 0.2 percent
inerts), was developed by Dow Chemical in the late 1950s as a structural fumigant. Vikane™ (currently manufactured
by DowElanco) possesses characteristics for the eradication of structure-infesting insects (Derrick et al. 1990). It is
non-flammable, non-corrosive, and does not cause undesirable odors. It quickly penetrates structural materials, is
effective against a variety of structural pests, and dissipates rapidly during aeration (Chambers and Mllard 1995,
Stewart 1957 and 1966, Kenaga 1957). This material is
an established structural fumigant, and therefore is
considered an alternative to methyl bromide. Since first
marketed in the United States in 1961, it has been used to
fumigate more than one million buildings, including
museums, historic landmarks, rare book libraries,
government archives, scientific and medical research
laboratories, and food-handling facilities (DowElanco
1994). Compared to methyl bromide, sulfuryl fluoride
penetrates structural materials more rapidly, and is
effective against a wide variety of pests, and leaves less
residue in materials after aeration. These characteristics
make it a viable alternative to methyl bromide in
structural fumigation (Derrick et al. 1990).
Benefits of Vikane™
Non-flammable, non-corrosive and does not
cause undesirable odors.
Easily dispersed into a structure and quickly
penetrates structural materials
Effective against a wide variety of pests
Does not form residues on fumigated materials
Dissipates rapidly during aeration
Sulfuryl fluoride is an excellent broad-spectrum fumigant, due to its toxicity to target pests, good dispersion
and penetrating qualities. It is commonly used to control a wide variety of household pests, including drywood and
Formosan termites (Bess and Ota 1960, Stewart 1957), wood-boring beetles (powder post beetles, death watch beetles,
and old house borers), fabric and museum pests (clothes moths and furniture and carpet beetles), cockroaches, bed bugs,
snails (Richardson and Roth 1965), brown dog ticks, and rodents (rats and mice) infesting buildings, furnishings,
construction materials, and vehicles (DowElanco 1996a, Kenaga 1957, Bess and Ota 1960, Roth 1973).
Fumigant Qualities Compared with Methyl Bromide
In many ways, Vikane™ can be a preferred structural fumigant over the use of methyl bromide: Unlike
methyl bromide, sulfuryl fluoride does not react with sulfur-containing materials to form off- or skunk-odors
(DowElanco 1996a). Vikane™ passes through nylon and polyethylene sheeting much more slowly than does methyl
bromide, so that the gas is easily confined by the plastic tarps commonly used in structural fumigation. Furthermore,
sulfuryl fluoride penetrates into and aerates from wood much faster than methyl bromide (DowElanco 1996a, Bond
1984, Grey 1960). Rapid penetration of substrates inhabited by the pests allows for variable (shorter) exposure times
compared with standard exposure times for methyl bromide (DowElanco 1996a). Lastly, because sulfuryl fluoride is
about 20 times less soluble in water than methyl bromide (i.e., 0.075 percent by weight at 77 °F (Meikle and Stewart
1962)), water can be used to form a barrier or bottom seal during the fumigation process (DowElanco 1996a).
-------
Efficacy
Sulfuryl fluoride is highly toxic to all post-embryonic life stages of insects (LTNEP 1994), eggs of most species
are less susceptible (DowElanco 1996a; Bond 1984). The efficacy of sulfuryl fluoride depends on the concentration
reaching the target pest and the duration of exposure. As a result, the dosage of sulfuryl fluoride required for a specific
pest is calculated in "ounce-hours," ounces of Vikane™ multiplied by hours of exposure. In general, insect eggs require
a higher ounce-hour dosage of sulfuryl fluoride compared to later life stages (i.e., a 10-fold increase in dosage for some
insect species) (UNEP 1992, UNEP 1994). However, the ability to control egg stages of social insects (i.e., termites
and ants) is not necessary because these newly hatched larvae cannot survive without adult care. Furthermore, the
higher dosages required to control insect eggs can be obtained by increasing the exposure time, concentration of sulfuryl
fluoride, or a combination of the two. Fumigators use a "fumiguide calculation system" to determine the amount of
Vikane™ required for specific pest and fumigation conditions (DowElanco 1994 and 1996a).
Sulfuryl fluoride prevents insects from metabolizing the stored fats they need to maintain a sufficient source of
energy for survival by disrupting the glycolysis cycle (Meikle et al. 1963). Mortality may be delayed for insects for
se%'eral days following fumigation (Osbrink et al. 1987), therefore insects that have received a lethal exposure to sulfuryl
fluoride may still be alive immediately following fumigation (no longer than 3 to 5 days for termites) (DowElanco 1994).
Sulfuryl fluoride has also been demonstrated to reduce oxygen uptake in insect eggs (Outram 1970).
Usage
Vikane™, a restricted-use pesticide, is currently registered to control certain pests in the following infested
sites: structures, fumigation chambers, construction materials and furnishings (including household effects), and all
vehicles except aircraft and subsurface water vessels (Derrick et al. 1990, DowElanco 1996a). Vikane™ is odorless,
colorless, non-flammable, non-reactive, and non-corrosive at temperatures normally encountered in structural and other
fumigations. As a result, it can be used to fumigate photographic supplies, metals, paper, leather, rubbers, plastics,
cloths, wallpapers, household furnishings, and a variety of other articles (Trinkley 1996, Derrick et al. 1990,
Anonymous 1980). It has little or no effect on the germination of weed and crop seeds; however, it is injurious to green
plants, vegetables, fruits, and tubers. Sulfuryl fluoride does not form toxic surface residues on household items, and thus
dishes, cloths, and other items do not need to be removed or washed following fumigation with Vikane™ (DowElanco
1994). It is not registered for use where food and grain commodities are present because food residue tolerances have
not been established. Guidelines for use of the fumigant specifically state that "under no conditions should Vikane™ be
used on raw agricultural food commodities, foods, feeds, or medicinal products destined for human or animal
consumption, or on living plants" (UNEP 1994, Bond 1984).
Application
To control termites, Vikane™ is applied to tarped or sealed structures for an exposure period of 2 to 72,
commonly 20-24 hours (the duration depends on fumigant and labor cost considerations and time constraints), followed
by a 6 to 8 hour aeration period (UNEP 1994). It is packaged in white cylinders as a liquid under pressure (99.8 percent
Vikane™ with no other pesticides, solvents, or additives); however, it volatilizes rapidly upon release from the cylinder.
Therefore, the gas is released under its own vapor pressure through tubing directly into the structure from pressurized
cylinders. The released sulfuryl fluoride is dense (3.5 times heavier than air), and will extract heat from the air as it
changes from a liquid to a gas. Fans are used not only to distribute Vikane™ throughout the fumigation area, but also to
as heat exchangers to mix cool air near the fumigation introduction site with surrounding warmer air to prevent
condensation of moisture from the air. Unlike methyl bromide, no auxiliary heat source is required (Stewart 1957).
As with methyl bromide, exposing sulfuryl fluoride to open flames can form acids which may react with
metals, glass, ceramic tiles, or china near the heat source. Thus, prior to structural fumigation, all open flames and
glowing heat filaments are turned off or disconnected (i.e., pilot lights, electric heater elements, or automatic switches)
(DowElanco 1994, Derrick et al. 1990). Once the appropriate amount of Vikane™ is introduced, the fumigator closes
the cylinder valve and removes the tubing from the cylinder. Concentrations of Vikane™ can be monitored during
fumigation using a fumiscope. Because sulfuryl fluoride is odorless and does not irritate the eyes or skin, trace amounts
-------
of a warning agent (e.g. chloropicrin, which causes irritation to the eyes, tears, discomfort, and has a noticeable
disagreeable pungent odor) are typically introduced into the structure prior to fumigation to act as a warning agent
(DowElanco 1994 and 1996a).
Because of a multitude of structural, environmental, and fumigation variations, no two fumigations are alike.
The required dosages of Vikane™ are influenced by the temperature at the site of the pest, the length of the exposure
period, containment or the rate the fumigant is lost from the structure, and the susceptibility of the pest to be controlled.
As a result, dosages vary, however a typical dry wood home fumigation uses 6-16 ounces (0.4 -1.0 Ibs.) per thousand
cubic feet. A specially designed Fumiguide™ calculator, which takes into account varying fumigation conditions (e.g.,
wind speed, relative humidity, tarp condition, volume in cubic feet being treated, soil type around structure, target pest,
fan capacity, and exposure duration), is used to determine the required fumigant dosage. Once the fumigation is
complete, the fumigator will return to the structure to conduct the aeration procedure (DowElanco 1994 and 1996a).
Aeration, the final step in a fumigation, requires proper ventilation and clearance of Vikane™ and the warning
agent from a structure. According to the Occupational Safety and Health Administration (OSHA) permissible exposure
limit (PEL) and the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV)
for Vikane™, the fumigator must aerate the structure so that the concentration of sulfuryl fluoride is 5 ppm or less prior
to reentry. Reentry must be approved by trained and state-licensed/certified professionals (DowElanco 1996a).
Because sulfuryl fluoride has a very high vapor pressure (potential to escape from an area) and a low boiling point (it is
a gas at -67 °F), it will quickly diffuse from high concentrations within a structure to the outside air where it rapidly
dissipates to non-detectible levels (Ultraviolet radiation and reactions with solid particles in the atmosphere catalyze the
breakdown of Vikane™) (DowElanco 1994).
The relatively small amounts of sulfuryl fluoride released are calculated to have virtually no impact on the
global atmosphere or environment. It is broken down mainly through hydrolysis to release fluoride and sulfide ions.
Because it is fully oxidized it does not interact with or contribute to local ozone formation. Furthermore, the relative
contribution of sulfuryl fluoride to acid rain is infinitely small compared to massive amounts of sulfur released to the
atmosphere from industry. Lastly, sulfuryl fluoride contains no chlorine or bromine and therefore does not contribute to
stratospheric ozone depletion (Chambers and Millard 1995, Baily 1992).
Toxicity
Sulfuryl fluoride is a toxic gas that can be handled safely by trained professional fumigators. This gas (as well
as methyl bromide) is acutely toxic to humans, although the severity of toxicological effects is dependent on the exposure
concentration and exposure duration. Short-term inhalation exposure to high concentrations may cause respiratory
irritation followed by pulmonary edema (an accumulation of fluid in the lungs, which can cause death), nausea,
abdominal pain, central nervous system depression, and numbness in the extremities. Chronic longer-term inhalation
exposure to concentrations significantly above the threshold limit value (TLV) may result in fluorosis (i.e., fluoride
binding to the teeth and bones) because sulfuryl fluoride is converted to fluoride ion in the body (DowElanco 1994).
Mammalian toxicity by inhalation is about equal to that of methyl bromide (Bond 1984).
Market Trends
Currently, sulfuryl fluoride is used in approximately 85 percent of all structural fumigations, while methyl
bromide is used for the remaining 15 percent (Sansone 1996). In California, fumigating dwellings with sulfuryl fluoride
has reduced the use of methyl bromide by more than 80 percent. For example, about 2,300 tones of methyl bromide
were used in 1990 compared with 430 tones in 1992 (UNEP 1994).
DowElanco supplies 100 percent of the Vikane™ structural fumigation market. The company is currently
involved in efforts to increase the use of Vikane™ gas fumigant in two selected markets: 1) quarantine fumigation
applications and 2) use in empty food processing facilities. Under current quarantine procedures (USDA-APHIS PPQ
Treatment Manual and the AQIS Cargo Container Quarantine Aspects and Procedures Manual), treatment rates for are
provided for fumigation of non-food cargo potentially infested with wood-infesting beetles. Efforts are currently
-------
underway to develop treatment schedules for additional target insect pests of non-food goods. An additional potential
quarantine fumigation opportunity for Vikane™ is the development of treatment schedules to fumigate timber being
imported into the United States, Europe, and Japan to control wood-destroying beetles and/or fungal pathogens.
Cost of Fumigating with Vikane™ vs. Methyl Bromide
A general picture of the kinds of fumigation costs associated with using Vikane and Methyl Bromide is
provided in the table below. Vikane™ application rates, (and the associated fumigant costs) are derived from the
DowElanco Fumiguide calculator system (DowElanco 1996a). This system uses a number of variables that can
positively or negatively affect the ability to achieve a lethal concentration. These factors include: the target pest (insect);
ground temperature at structure site; structure size; the duration of the fumigation; the foundation type of the structure
(slab, crawl space, basement, etc.); and whether or not the fumigation will be monitored. A fumigation performed in
warmer months, on larger structures, with a slab foundation or a basement, can be more cost efficient than a comparable
fumigation using methyl bromide. As indicated by the figures in the tables below, monitoring sulfuryl fluoride levels to
confirm lethal dose during the fumigation utilizes less chemical and is less expensive than fumigation without
monitoring.
The following cost breakout examples are for a 35,000 cubic foot structure - a typical home (Table 1), arid for
a 250,000 cubic foot structure - a commercial structure (Table 2). Cost estimates are for non-monitored and monitored
(in parenthesis) fumigations. Label rates for methyl bromide range from 1 to 3 lbs/1000 ft3. The examples listed below
use the 1 lb/1000 on a slab foundation and 2 lb/1000 for.a structure with a crawl space. The conditions for these
examples were: Tarp = good; Seal = Good; Wind = 4mph; Crawl space = sandy loam. The temperature was 75° F and
a 24 hour exposure period. The dosages for these examples were calculated on the Fumiguide electronic calculator.
These examples are for fumigations to eliminate drywood termites. Fumigating for other insects (like powder
post beetles or wood borers) would increase the amount of fumigant required for Vikane™. There are additional costs
that are not considered in these examples. These costs include: 1) Extended aeration times for methyl bromide may
require additional manpower and equipment costs for the fumigator. There will also be costs absorbed by the structure
owner because the extended aeration period delayed re-occupancy. Methyl Bromide costs for homes would include four
nights hotel room rental (1 during fumigation + 3 for aeration) compared to 2 nights (1 during fumigation + 1 aeration)
for Vikane™. 2) There also may be potential replacement costs for material which may react with methyl bromide to
cause odor problems in fumigated structures.
-------
Table 1. Vikane™ vs. Methyl Bromide Costs for a Typical Home (35,000 ft3).
CM* ,
Factors
Expense
Price/Pound
Fumigant
Costs
Clearing
Equipment
Total Expenses
Treatment*! ' ' :
Vnme
Crawl Space
(Monitored)
$9.00
$312.30
($234.90)
$2.40
($3.30)
S314.70
(S238.20)
Slab Foundation
(Monitored)
$9.00
$118.80
($89.10)
$2.40
($3.30)
$121.20
($92.40)
Xraftnwot&t,
Metfeyl Sroisilde
C$/l,OOOft2),
Crawl Space
$2.75
$192.50
$42.50
$235.00
Slab Foundation
$2.75
$96.25
$42.50
$138.75
Table 2. Vikane™ vs. Methyl Bromide Costs for a Commercial Structure (250,000 ft3).
' €«wt
Factors
Expense
Price/Pound
Fumigant Costs
Clearing
Equipment
Total Expenses
Treatment #1
' Yikane - ,
OMMWfft
Crawl Space
(Monitored)
$9.00
$1,371.60
($1,028.70)
$2.40
($3.30)
$1,374.00
($1,032.00)
Slab Foundation
(Monitored)
$9.00
$747.80
($561.60)
$2.40
($3.30)
$751.20
($564.90)
Treafa»arf;#2 , ;
M*ihy.JBr»i»Me !
-------
References
Bailey 1992. Sulfuryl Fluoride: Fate in the Atmosphere. Dow Chemical Company. DECO-ES Report 2511. Midland,
Michigan.
Bond 1984. Manual of Fumigation for Insect Control. E. J. Bond. FAO Plant Production and Protection. Paper 54.
Bess and Ota 1960. Fumigation of Buildings to Control the Dry-Wood Termite, Cryptotermes brevis. H.A. Bess and
A.K. Ota. Journal of Economic Entomology. Volume 53, Number 4, pp. 503-510.
Chambers and Millard. 1995. Assessing the Global Use Potential of Sulfuryl Fluoride. 1995 Annual International
Research Conference on Methyl Bromide Alternatives and Emissions Reductions. November 6-8. San Diego,
California.
Derrick et al. 1990. Sulfuryl Fluoride (Vikane): A Review of Its Use As a Fumigant. M.R. Derrick. H.D. Burgess,
M.T. Baker, and N.E. Binne. Journal of the American Institute for Conservation. Volume 29, Number 1 (Spring 1990),
pp. 77-90.
DowElanco. 1994 (November). General Information on Vikane Gas Fumigant. Form No. 311 -56-077
DowElanco. 1996a. Vikane™ Gas Fumigant Structural Fumigation Manual.
DowElanco. 1996b. Vikane™ cost comparison to methyl bromide data.
Grey 1960. Vikane™ — A New Fumigant for Control of Drywood Termites. Henry E. Gray. Pest Control Magazine.
Volume 48, Number 10, pp. 43-46.
GLCC 1987. Directions for US of Meth-O-Gas 100" and Meth-O-Gas *. Great Lakes Chemical Company.
West Lafayette, Indiana.
Kenega 1957. Some Biological Chemical and Physical Properties of Sulfuryl Fluoride as an Insecticidal Fumigant. E.E.
Kenega. Journal of Economic Entomology. Volume 50, pp. 1-6.
Meikle and Stewart 1962. Structural Fumigants, the Residue Potential of Sulfuryl Fluoride, Methyl Bromide, and
Methane-Sulfonyl Fluoride in Structural Fumigations. Journal of Agriculture and Food Chemistry. Volume 12, p 464-
467.
Meikle et al. 1963. Drywood Termite Metabolism of Vikane Gas Fumigant As Shown by Labeled Pool Technique.
Journal of Agriculture and Food Chemistry. Volume 11, pp. 226-230.
Osbrink et al. 1987. Laboratory Comparisons of Sulfuryl Fluoride Toxiciry and Mean Time of Mortality Among Ten
Termite Species (Isoptera: Hodotermitidae, Kalotermitidae, Rhinotermitidae). Journal of Economic Entomology.
Volume 80, pp. 1044-1047.
Outram 1970. Some Effects of the Fumigant Sulfuryl Fluoride on the Gross Metabolism of Insect Eggs. Fluoride.
Volume 3, pp. 85-91.
Richardson and Roth 1965. Methyl Bromide, Sulfuryl Fluoride and Other Fumigants Against Cochlicella and Pheba
Snails. H.H. Richardson and H. Roth. Journal of Economic Entomology. Volume 58, pp. 690-693.
Roth 1973. Fumigants for Quarantine Control of the Adult Brown Dog Tick: Laboratory Studies. Journal of Economic
Entomology. Volume 66, Number 6, pp. 1283-1285.
Sansone 1996 (August). Personal Communication. JohnSansone. SCC Products, Inc. Anaheim, California.
-------
Stewart 1966. Balanced Fumigation for Better Termite Control. Doane Stewart. Down to Earth. Volume 22, Number
2, pp. 8-10.
Stewart 1957. Sulfuryl Fluoride — A New Fumigant for Control of the Drywood Termite Kalotermes Minor Hagen.
Doane Stewart. Journal of Economic Entomology. Volume 50, Number 1, pp. 7-11.
Trinkley 1996 (August). Personal Communication. Mike Trinkley. Chicora Foundation, Inc. Columbia, SC.
UNEP. 1992. Methyl Bromide: Its atmospheric science, technology, and economics. Montreal Protocol Assessment
Supplement. United Nations Environment Programme. June.
UNEP. 1994. Montreal Protocol on substances that deplete the ozone layer. United Nations Environment
Programme. 1994. Report of the Methyl Bromide Technical Options Committee. 1995 Assessment. EPA 430.
*U.S. Government Printing Office: 1997 - 516-454/83517
-------
------- |