&EPA
United States
Environmental Protection
Agency
Office of Water
(4503F)
EPA841-F-97-002
October 1997
Number 3
Watershed Protection:
Clean Lakes Study
Use of Aquatic Weevils to Control a
Nuisance Weed in Lake Bomoseen,
Vermont
Key Feature:
Project Name:
Location:
Scope/Size:
Land Type:
Stressor:
Stressor Source:
Data Sources:
Data Mechanisms:
Monitoring Plan:
Control Measures:
Use of a biological control for a nuisance macrophyte
Lake Bomoseen
Rutland County, VT
USEPA Region 1
Watershed area 10,025 hectares (24,470 acres)
Lake area 960 hectares (2,370 acres)
Ecoregion #60, Northern Appalachian Plateau and Uplands
Eurasian watermilfoil (Myriophyllum spicatum)
Accidental introduction
State
Plant and invertebrate sampling
Yes
Aquatic weevil Euhrychiopsis lecontei
Summary: Lake Bomoseen, located in western Vermont (Figure 1), has had a long
history of weed problems. By the early 1980s, Eurasian watermilfoil {Myriophyllum
spicatum) was the dominant weed species in the lake. Eurasian watermilfoil is an
introduced species that is difficult to control due to its ability to survive in various
Figure 1. Location of Lake
Bomoseen, Vermont.
environmental conditions. At one point the watermilfoil covered 240 hectares of the lake, impairing its recreational and
commercial uses. In addition to Lake Bomoseen, the macrophyte has been documented to exist in approximately 42 other
Vermont lakes. One of those is Brownington Pond (located in northeastern Vermont), which experienced a decline in its
watermilfoil population in 1989. Following the discovery of this natural decline, the Vermont Department of Environmental
Conservation (VTDEC) was awarded a U.S. Environmental Protection Agency (USEPA) grant to investigate the decline and
its causes. It was hoped that the investigation would benefit other lakes with Eurasian watermilfoil problems.
Researchers from Middlebury College, working under contract for VTDEC, documented fluctuations in the Brownington
Pond Eurasian watermilfoil population and then investigated possible causes, including the role of herbivores. The researchers
concluded that a native aquatic weevil, Euhrychiopsis lecontei, was largely responsible. They proceeded to examine the
specific effects of the weevil on the Eurasian watermilfoil and native plant species to determine the feasibility of the weevil as
a biological control. The weevil was deemed appropriate and potentially effective as a control for the Eurasian watermilfoil
and the weevil population in Lake Bomoseen was augmented (i.e., added to) in 1993 and 1994. Although an overall reduction
in the Eurasian watermilfoil population dramatic enough to be noticeable to lakeshore owners has not yet occurred, the
technique has shown promise in controlling the growth of the weed. Results from the monitoring of introduction sites have
shown that over the last 4 years weevil survival has been good and that the plants have suffered extensive weevil-induced
damage. These initial results indicate that, over time, the weevil might be able to reduce nuisance growth in Lake Bomoseen
and could potentially be used in other lakes with similar problems.
Contact: Betty Hutchinson, Vermont Department of Environmental Conservation, 103 South Main Street,
Building 10 North, Waterbury, ₯^05671-0408, phone K802) 241-3777
-------
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personal communication, 1997).
invertebrates than do native aquatic plant beds
(Sheldon, 1995; Sheldon and Creed, 1995). In
i:^ j :|<|i ei 'addition to,h|effects.,pn.aquatic life, EWM hinders
i ,,ii ',,,, 'i,,-!,, ', f«li ,,ii,i,ir i:,:ii,:i:' l,!,,v!l, , i::,' III'!,') Ilili, II',: ,- , ,, ,
:;"!"'1; i ;'];:"?r~i: 'the use of waters, .f^r.recreatipnal boating, swimming
and, fishing.
" i ..... t ' ' :!| - s": ' ......... , p. ..... i"'" ieili i: ':,
li: ...... : ...... li ..... Ii! ......... LiM ....... ^:A±:L
T i,, f '
Liiii ....... -Al
aquatic weed growth has been a consistent
problem in Lake Bomoseen since the early 1940s. In
J977 t|e town of Castleton.Regain toiharvestthe
tn| exptiq weedi speciesiin^the laJce, curly leaf
^^^^^E^^£fif°^,1'H;s£?ff}' The'weeH'
i §I?oF^e
^^L^^^^^^^l^T^ l^v^S^^^^^
then c6ntinue3 with state and local funds and was
__ ^J.,_J^__^ | ^|,,^|_ ,_J|_^, ,_g|,,,,gL,_
Sarly 1980s, when Eurasian wateniilf oil
,,p^_^^^_,,_,^^ ..... ,^
EWM) replaced P. crispus as the dominant species in
lalel" .......... l^cIiwlt^Faerye^Ong^as1 remained 3ie
., 'III! ViJ . .,'.''. ' ' . I'1 . " A III '" ni. f'> ....... ' ..... "I .III. . .I'll'.*'. ' ...... Ji'i'li ........ ..I ....... ..ni|',.i,!',|.. II hi ,., Jill ......
method for the control of EWM on Lake
^
........
its accidental introduction in the mid-1900s,
BWM has spread to at least 40 states and 3 Canadian
, | :;, ii'g!,"1;"' : ;:,,*;,, ,,h , ,,,, M , , |M|, , , i|nili ll|ni , , , ,, Ll,, ,, liin||i
provinces, making it one of the most widespread
jiuisance macrophytes" in jWprtli America ''
frequently becomes the dominant species in a lalce.
The widespread distribution of EW^l can be
Figure 2. Eurasian watennilfbil.
-------
IDENTIFYING POSSIBLE CONTROLS
In 1989, biologists with the Vermont Department of
Environmental Conservation (VTDEC) noticed a
natural decline in the population of EWM in
Brownington Pond in the northeastern region of the
state. In 1990, VTDEC was awarded a $575,000
grant from the USEPA under section 314 of the
Clean Water Act. The purpose of this grant was to
examine the possibility of using aquatic herbivores
found in Brownington Pond as a biological control
for other EWM populations. This Clean Lakes
Demonstration Program grant was awarded for the
purpose of highlighting new and unique techniques
for lake restoration.
Working under contract for VTDEC, researchers
from Middlebury College mapped and studied the
decreases and increases in EWM hi Brownington
Pond from 1990 through 1995. The
study investigated a variety of factors
(e.g., herbivores, water chemistry, and
sediment chemistry) that could have
influenced the fluctuations. The results
of the plant and invertebrate sampling
suggested that herbivorous insects
played a primary role in the EWM
declines observed in 1989 and 1992.
The researchers were able to eliminate
other factors as reasons for the declines,
and the focus turned toward the
herbivore populations hi the pond.
FigureS. An adult milfoil
weevil (illustration courtesy
of Susan Warren, VTDEC).
The two main EWM herbivores present in
Brownington Pond were an aquatic weevil native to
North America, Euhrychiopsis lecontei (Figure 3),
and the caterpillar Acentria ephemerella. In
examining the herbivores, the researchers noticed
variations in the abundance of the aquatic weevil
between 1990 and 1994 and compared the variations
to those of the EWM. They noticed that the
fluctuations in the weevil populations compared to
the EWM populations were similar to those exhibited
by predator-prey or host-parasitoid models (Creed
and Sheldon, 1995). The evidence suggested that the
naturally occurring weevil populations might have .
played a role in the decline of the Brownington Pond
EWM population.
The Middlebury College researchers conducted
laboratory and field experiments to further examine
the relationship between EWM and the weevils, as
well as their relationships to other herbivores and
macrophytes. It was discovered that Phytobius
leucogaster, another species of aquatic weevil, did
feed on the EWM but had no significant negative
effect on its growth (Sheldon, 1995). It was also
discovered that the Acentria larvae reduced EWM
growth in laboratory experiments (due to stem-
cutting during feeding and retreat construction
(Creed and Sheldon, 1994)). However, extensive
caterpillar damage was not observed in Brownington
Pond (Creed and Sheldon, 1994).
By researching the feeding behaviors of the weevil,
the researchers were able to determine that all of its
life stages can cause damage to the plant. The first
instar larvae cause extensive destruction to the
growing tip of the plant, thus preventing
new stem growth. The late instar larvae
hollow out the stern by feeding on its
vascular tissue, thus reducing the plant's
ability to transport the nutrients necessary
for growth. The late instar larvae also
destroy the lacuna! system of the EWM,
which serves as a gas reservoir for
respired carbon dioxide (Nichols and
Shaw, 1986, as cited in Creed and
Sheldon, 1994) and also permits gas
exchange between the plant roots and
shoots (Grace and Wetzel, 1978, Nichols
and Shaw, 1986, as cited hi Creed and Sheldon,
1994). The adult weevils can damage the plant by
feeding on its upper leaves, which can affect the
plant's energy balance by transferring
photosynthesis responsibilities to deeper leaves
(Creed et al., 1992). The feeding may also make the
plant more susceptible to infections by bacteria and
fungi (Sheldon and Creed, 1995; Creed et al., 1992).
In addition to these direct effects, larval tunneling
can also cause the plant to lose buoyancy and
collapse into deeper waters, where it is subject to
conditions different from those at the surface. This
indirect effect of loss of buoyancy could in fact be
more significant than the direct loss of leaf and stem
tissue discussed above (Creed and Sheldon, 1995;
Creed et al., 1992). It can cause the plants to sink
out of wall-lit surface water, possibly to depths with
insufficient light for photosynthesis (Creed et al.,
-------
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fl4l ...... i
i ];!!'! i1', ''
, "i!1:1:;!1, .iv:
' ,5, ..... ....... ,{
jjjii;^^^ ..... i^jl
- ; '.i-1:*
||992|j giants that lose buovancy^ due to weevil
could also entangle and sink other,
"lgaaniaj|ea giants.
deeTneH acceptaBIenBy y>p£)]gc ^ ^-^ experimental
Biological Control Because of the possibility that it
might be able to control EWM and the low risk it
The Middlebury College researchers conducted
posed to mm^targeTnative aquatic plants.
assess the
we're'
eggs, land*
:" ssi1!-!! ! ; & " ' S S """ "5" 1
other material. Data were collected concerning the
INTRODUCTION OF A BIOLOGICAL
CONTROL AGENT
length. The plants
i
"w gnace n ecyinders n
twbl ..... &rt5uradint ..... weevHs ..... were ..... addleif'tb'each1
2 ..... ; ..... ii! .............. M, ..................... I [[[ I ........ I .................... I ..... I ............................................... I ..................................... I ...................................... Ill .................................
The resu'15 o
that tlie'wet weight "of tfie'EWM''averaged 50
mte"two-weevil containers 3ian" in the
cont^ers^I',130 percent less in 'the
SI" coptaineri pgeWonJ 1995). "'Jn' addition^'
In the summer of 1993, VTDEC issued a Biological
Control Permit under the state's Aquatic Nuisance
Control Permit Program allowing the release of
weevils into two Vermont lakes, including Lake
Bomoseen1 (Sheldon, 1995). Rearing of the weevils
took place at VTDEC's environmental laboratory in
Waterbitry and at Middlebury College.
11 average of 25
orter ..... th'e ..... jee-v'| cotaSners and ..... 0
r-weevil ..... containers
= (S'heldon;'l9^);
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;:;"' I, fjui^, ",;iri-«r*;:.ty: -i- :|| i&],4 j^jft ,:$?,$$ ] ';;>. ^j:OSI
In field experiments, weevils were added to 30.5-
""i'-'-iii a S'"! I' 51* «
two lakes ...in w.
days
weevwere not
e weevis
S ..... the ..... three"' Sxp'Smenlal ..... weevil
'
In the summer of 1993, more than 5,000 weevils
were added to three unharvested sites in Lake
Bomoseen Cedar Mountain, Neshobe Island, and
Eckley Point2 (Figure 4). In the summer of 1994,
^^^^|m^e^y ^(jgo additional weevils were
introduced to the same three sites by both VTDEC
and Middlebury College. The distribution of the
Weevils released in 1994 was 9 percent eggs, 77
percent larvae, 13 percent adults, and 1 percent
s (Hanson et al
. ........
r for the
control enclosures. Jriant weignis were lower
.1 j i ! ilf;iiii!ij-l>Lr!' IrltJ .»!]<: . ail!!!!!!!!!1' i-i'l!!iu!S. 'i '" ,
plants with weevils. In addition, the macrophyte
"* ' : ''-'L'", in" the control enclosures and the
Su"rro"lunding 'areas, "but in""the weevil enclosures "there
gplants at the water surface (Sheldon and
^X, $£ plants; feadcoiiaps
| ast 1 ''meter below" the surface
Weevils were added to the three unharvested sites in
Lake Bomoseen at least once a week throughout the
summers of 1993 and 1994. Data were collected
concerning the numbers and life stages of weevils
:i?5): ;
li^^^^^^^ \
p^^^.jj^.___._.|._ _!££. £nvesjjga'|eg t|je effects of
damage was recorded at each site on each release
date. Each augmentation area was paired with a site
that acted as the control "no-weevil" site for later
: c'gJfgjIgjQg ^u^g^hVmraitonng'e'fforts. " " '
quatic macrpphytes,;
"'"'"''" 1 species. Tn'ey found that
vranatve
' ' "'!]»' ',' jli, . , ,i" ; i ; , h IJHJBIj f " I ff ,||| ,,. ,|, , T , r Sh n n,| , i , i. | , , |i ,, .
' had no significant negative effects on "the
:"oF
the weevils qiq'!ee"ana~liy"eggs
:on^'pdrtions;'or the native watermilfoil M. sibricum^
the resulting damage was not considered significant
i1 ' ! ' iSiif'i'il! i ''" l'M1 " *ir, .mull i r!JT, ,.
in;
iThe introduction of weevils into Lake Bomoseen
..... |-r ............. ^ ........ t f|| ........ : ..... ni|||l ........ ................... ......... -M : .................... ............. ................... t4ii\^CH_fcY L/X^/O^AAb Al* (J.AV* JIU
ed, 1995; Sheldon, ...... 1995^
, ' ' f ' -S ',' ' ' ; , If °i| ^jjjji 'j^ii^j^: ^jjs?!;iii§^y> ilf >; 'If;';;1 9 ^. '^al^.' 'for '|ck|
was actually an augmentation because weevils were
already present in the lake (although in low abundance).
. . , , ,
Based on the results from the Middlebury College
laboratory and field experiments, the weevil was
ley Point are excluded. It was
suspected that factors other than the introduced weevils
influenced the condition of the EWM at that site.
-------
CRYSTAL BEACH
Key
Site* wtwre the weevil,
Euhrychicpste'licontoi,
has b«en rotated
R»hwie)WHdHf»
NMhotofelandSlta
Ecktey Point Site
C«»ar Mountain Site
LAKE BOMOSEEN
LOCATION MM»
Figure 4. Lake Bomoseen introduction sites.
RESULTS
successfully established in the Lake Bomoseen sites.
Since the initial release on June 30,1993, over
20,000 weevils have been placed in Lake Bomoseen.
Data collected in 1993 and 1994 show that the total
number of weevils collected at the augmentation
sites was greater than in the "no-weevil" sites and
greatly increased from one year to the next (Table 1).
These findings indicate that the weevil is surviving
and thriving in the environment. Table 2 shows that
the EWM biomass at the Cedar location was
substantially less in the augmentation area as
compared to the "no-weevil" control area (although a
similar result was not observed at the Neshobe
location). There was less EWM in both
augmentation sites at the end of 1994 compared to
1993 (Table 3).
Table 1. A comparison of overall total number
of weevils collected on stem transects in Lake
Bomoseen at augmentation and control sites
between 1993 and 1994.
Location
Cedar
Neshobe
Augmentation
sites
1993 1994
34 73
28 80
No-weevil
control sites
1993 1994
25 32
23 54
Source: Sheldon, 1995.
Monitoring was conducted through 1995 at the
augmentation sites. Monitoring consisted of
collecting stem samples for weevil counts during the
summers and quantitative plant and invertebrate
samples at the end of each summer. The stem
samples were examined, and all weevil eggs, larvae,
pupae, and adults were counted and removed. Three
random plant samples were collected at the end of
the summers from each of the six unharvested areas
for examination of plant health and growth. Weevils
were counted and, along with other invertebrates,
removed. The plants were then dried and weighed.
In addition to collection of samples, visual
observations were made of the sites to assess the
effects of the weevils. Throughout the sampling
periods, apparent weevil damage was noted at all
sites in Lake Bomoseen.
The results of the quantitative analysis of the
collected samples suggest that the weevil is
Table 2. Results of 1994 quantitative invertebrate
and plant sampling in Lake Bomoseen (means ± 1
S.E.) after 2 years of augmentation.
Augmentation sites
Location
Cedar
Neshobe
dry wt
(g)a
21.32
(1.96)
34.59
(7.94)
#
weevils b
0.67
(0.44)
1.33
(0.44)
No-weevil
control sites
dry wt
(g)
30.22
(2.88)
27.96
(6.46)
#
weevils
2.33
(0.44)
1.00
(1.33)
"Weights are total dry weight of Myriophyllum spicatum.
'Number of weevils per sample plant.
Source: Sheldon, 1995.
-------
Table 3. Comparison of '1(993 and 1199^ EWM
biomass at weevil augmentation sites in Lake
Bomoscen.
T!| '""i! l!! Source; 's
,:AjltfiQUgn the conclusions
'
iwn from the Lake
increased
^eevil populations and the decreased EWM biomass
al the weevil introduction sites m Lake Bomoseen
:i: ^,1,1,,,,;,: ; j||!,:|,!i; a t is; ;,!,::; \xj^j^.t n.' iiiii' I'-Mnni'jJ« «'«i»:-j »« -JP , ,<»- *' v
^4wggest that the weevil may be able to limit the
""'''
'in'ffnegative effects on
iaver>tlus^ ^ _"_"
'" iLJL t as "opposed to other
icse greliminary results suggest that
contro
Vt and" could provide a"unique management
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' f for lakes with problems sumlar to those
i by Lake Bomoseen.
ax;
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OTHER EXAMPLES OF WEEVIL-
ASSOCIATED EURASIAN
WATERMILFOIL DECLINES
Fish Lake, Wisconsin
At least three lakes in Wisconsin have
experienced EWM crashes that are believed to
be associated with the aquatic weevil
Euhrychiopsis leconteiDevil's Lake in Sauk
County, Lake Wingra in Dane County, and Fish
Lake in Dane County (Lillie and Helsel, 1997).
Of the three, Fish Lake is the best documented
case of an EWM crash.
Fish Lake, a 100-hectare (247-acre) seepage
lake located in the northwest corner of Dane
County, was the subject of an extensive fish
research-management study conducted by the
Wisconsin Department of Natural Resources
(WDNR). The study included monitoring of
EWM beds from 1991 to 1995.
During the early years of the study, EWM
covered approximately 40 hectares (100 acres)
or nearly 40 percent of the total lake bottom
(Lillie, 1996). In 1991, EWM represented 93
percent of the total plant biomass in the lake;
that percentage decreased to 77 percent by 1994
(Lillie, 1996). EWM biomass in all vegetated
sites of the lake decreased from 532 g/m2 in
1991 to 268 g/m2 in 1994 (Lillie, 1996). These
substantial declines in biomass and its relative
dominance indicated that the population in Fish
Lake was in the process of crashing by 1994.
These declines continued in 1995.
During the study, a large population of weevils
was documented to exist in Fish Lake. Given
the occurrence of the weevil in the lake and
documented feeding habits of the weevil (Creed
and Sheldon, 1993,1994; Creed et al, 1992;
Newman et al, 1996a), it is possible that the
weevil is largely responsible for the continual
decline of EWM populations in Fish Lake.
::-
-------
I McCullom Lake, Illinois
McGullom Lake is a 99-hectare (244-acre) glacial
lake in the Gity of McHemy in northeastern
Illinois, A Phase I Diagnostic/Feasibility Study
was conducted for McCullom Lake from 1989-
;1992 lender a grant from U:S. EPA's Clean Lakes
Program. This .study identified many factors
affectinglhe lake's ecology and recreation,
including colonization of the lake by EWM.
In 1993, the City of McHenry received a Phase H
Restoration/Implementation grant from the Clean
Lakes Program, thereby enabling it to implement-
the restoration and protection strategies identified
in :the Phase I study. An important part of the
Phase II project was to re-establish a balanced
community of aquatic plants since EWM had
spread to about 70 percent of the lake by the
summer of 1994 and was choking out many of the
native plant species.
Because of the lake's small watershed (249
hectares [616 acres]) and limited motorized
swatercraft access, the potential for EWM re-
infestation was deemed comparatively smallbut
only if the existing EWM growth could be
completely eliminated (or close to it).
Consequently, a "one-time" herbicide application
was planned to selectively remove the existing
EWM plants. Future re-infestations would be
controlled at an early stage through hand pulling,
and other non-herbicide control strategies. i
However, just prior to the herbicide application in
early spring 1995, almost no trace of EWM could
be found. Soon after, the aquatic weevil
Euhrychiopsis lecontei was identified on a few
floating fragments of EWM. These fragments
(and the isolated EWM beds that later emerged)
exhibited extensive damage characteristic of
weevil activity.
TheEWM has remained suppressed well below ,
nuisance levels through 1996 and 1997. The
McCullom Lake Clean Lakes Program grant H
recently has been extended for an additional year
to continue monitoring the EWM and weevil
communities and to document their interactions,
(Source: Robert Kirschner, personal communication)
Cenaiko Lake, Minnesota
Ongoing research supported by the Minnesota
Department of Naftirai'Resbiirces(MNDNI^;
and conducted byresearchers at the University
of Minnesofe is examining the possibilities of
th^ weevil JEuryhchiopsis lecontei as^^
biological 'control agent for EWM. Researchers
have examined nine lakes (eight in Minnesota
andjOne in l^isconsin) thafchad existing EWJM
and weevil populations.
Of the nine sites, the most pronounced weevil
infestation was found in Cenaiko Lalce in Anoka
County, Minnesota. Weevils caused severe
damage ;b the EWM plants in Cenaiko Lake,
most likely resulting in, the plants' decreased
abundance, EWM biomass (wet weight) at
Cenaiko Lake declined from 974 g/m2 in July
1996 to 239 g/m2 in September 1996 (Newman
et al., 1996b). ^Researchers estimate tihat the
biomass in June 1996 (before sampling) was
close toS2,(X)0 g/m2 (Newman et al., I996b). In,
luly 1996, feWM was approximately 50 percent
of the td^al plant biomass in the lake; by
September 1996, this value had decreased to 14
percent.
Monitoring of Cenaiko Lake did not begin until
June 1996 when a dense population of weevils
was discovered during reconnaissance studies
for/introduction sites (Newman et al.,1996b).
Cenaiko :Lake was then .added to the list of
regular sampling sites. Plant samples collected
atCenaiko Lake, as well as at other ^ites,-were
processed for invertebrates, plant biomass, rand
stem damage.
Because monitoring is still ongoing, sampling
and data are limited for this study. However,
the preliminary results indicate the weevils in
Cenaiico Lake may be responsible for the natural
decline of EWM.
-------
Lillie, R.A., and D. Helsel. 1997. A native weevil
«li;'t|acksEurasianwateinilfoil. Wisconsin
.', ?TG^ P!R! NewrotEJ an₯O9iIe; 1 "979^ The
|: |to|ojy of Canadian weeds!' 34. Myriophyltum
spicatttm JL. Canadian Journal ofJJ^tarii Science.
59;20i-2l5. Cited in She!3on and Creed^ 1995.
Department of Natural Resources Research
Management Findings 4Q(Maicti): 1-4.
y; i | | ;; ,,_ i,,,; i ,, p: ,i,||,|
j|j||3r j ^-p- gg-j|-.-£ g-||7^jj^-
| ="! ::i i* I59£ ^e'efiect of fterbivpreCeding oh the
Buoyancy or* Eurasian Watennilfoil. Journal of
' 30:75-76.
Nichols, S.A., and B.H. Shaw. 1986. Ecological life
fi-'hjstpries of the three aquatic nuisance plants,
the effect
isiiilc^, |fci JSs^SJPiH^fe:
_ y a""]
Euhrycfuopsis lecontei, on Eurasian watermilfoil
yrhjj>i}yjfam sP?ca*umy A.(juat*c B°tany_ 45;245-
ispicatum, Potamogeton crispus, and
Elodea canadensis. Hydrobiologia 131:3-21. Cited
in Creed and Sheldon, 1994.
fSifiN^ewmarij R.Mrz K.L. Hobnberj, D.D. Biesboer, and
g ,g. jj^nn^ |^g*' 'Effects of a potential
biocontrol agent, Euhrychiopsis lecontei, on
Eurasian watermitfoil in experimental tanks.
Aquatic Botany 53:131-150.
"""Creed, EKt JE', and S".P. Sneldon.'" 'f^S.' "Weevils
iiii!!
ervore
! die decline of an exotic weed? Ecological
ON I *> ''H1'" "' **/^Hi'' - '!"- -I ' -"t'lIC L'1!!!!" '" !' I' I1' ' 'll»"'JI "l"l"" l;
Applications 5(4):
., D.W. Ragsdale, and D.D. Biesboer.
.""^are Eurasian Watermilfoil Be Managed in
"Sfiiinesoia by Biological Control With Native or
Naturalized Insects? third progress report to the
Minnesota Department of Natural Resources,
Ecological Services, St. Paul, MN.
'|r ;,;' | ilij, "''. '''!"" ',...; i,ii|i|||.'i. ,, h i iiNl'/niij . ... ...... .. ..... :|', IV!M,,||,,.I, ..... .,., .,.; ..... ,,.,,, ,,
Sheldon, S. 1995. The Potential for Biological
Control of Eurasian Watermilfoil (Myriophyllum
spicatumj 7990- 1 995. Final report. Department of
, Middlebury College, Middlebury, VT.
R.G. Wetzelv ;i978./the production
urasian' watermilfoil: a review. Journal
Plant Management !6:1-1T. Cited in
Aeed and Sheldon, 1994.
'' '"""! "'" '" " ' '''"''"1'""'' '''""
Sheldon, S.P., and R.P. Creed, Jr. 1995. Use of a
native insect as a biological control for an introduced
Weed. Ecologi cal Appli cations 5 (4) : 1 1 22- 1 1 32.
I ~^3r.i'';L :: ., aisn-i;'".. ;/!" +*' ,;>!i " "'-n -/ -.. v iv/1" w
I, '^^-I&^lySfiSlisofthe Herbivorous Aquatic Weevil,
:^^^5!^nr;^mi;^s!sT5cOTiteX in Vermont.
1 ' ,i!"" in*^ ' ' ' '.' 1'111"'1"1 ' i!1''' fii"» '' '' ^' '!!'''' i|1"'1 ' 3" i"5i» '»
§niitE CM!* and J.W."Barko.' 1990! Ecology of
Eurasian watermilfoil. Journal of Aquatic Plant
Management 28:55-64.
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Cepartmeht of1 Environmental ConservaHon,
jg^ ii t ; |E::;::: g i il i :
C I;,
r! R! 1997PereOTaTcoijncarlon'.
JNfatural Resources Department, Northeastern Illinois
Planning dommission,"'dScago," it. July 16,1997.
;'"' ' ' ':":1 ' ' ' ! i i' ;:"' :""';.fi "T "!' ';:: ';;f'" 'ii'1:"l:
Lillie, R.A. 1996. A quantitative survey of the
floating-leafed and submersed macrophytes of Fish
Site Dane County, Wisconsin. Transactions of the
Wisconsin Academy of Arts and Sciences 84:111-
125.
I in ii i
This case study was prepared by Tetra Tech, Inc., Fairfax,
VA, under the direction of Anne Weinberg in EPA's Office
of Wetlands, Oceans and Watersheds, Watershed Branch.
The authors extend their appreciation to those who helped
to review the case study, especially Robert Creed at
Appalachian State University and Holly Crosson of the
Vermont Department of Environmental Conservation. To
obtain copies of this case study, contact your EPA Regional
Clean Lakes Coordinator, or request a copy from:
Nations! Center for Environmental Publications and
Information (NCEPI)
11029 Kenwood Road, Building 5
Cincinnati, OH 45424
FAX (513) 489-8695
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