United States
                    Environmental Protection
                         Office of Water
October 1997
Number 3
Watershed  Protection:
Clean  Lakes                Study
Use of Aquatic Weevils to Control  a
Nuisance  Weed  in  Lake Bomoseen,
  Key Feature:
  Project Name:


  Land Type:
  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
 Plant and invertebrate sampling
 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

                                                                  	nr	!"':n""	:	:"' in	n	a	:	:	
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	 i 	 1 	 inl i X1TT'J'~tY*rf'1\TT)L!I₯tiv  -•	 	i	
 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.


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.,

             , l!:f;Jl!;,T
v'!||!i llil;!;1!
                                                   fl4l ...... i
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                                                                        , "i!1:1:;!1, .iv:
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                                  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
                                                eggs, land*
        	:"•	ssi1!-!!	!	;	&	"•	'	S	S	"""	"5"	1	
         other material. Data were collected concerning the
                                                                  INTRODUCTION OF A BIOLOGICAL
                                                                  CONTROL AGENT
                                       length. The plants
        "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^);	
         "• *  '	 fliRI	"fi M ••	•'", "•'  »,n "•  - ""iiiiiiijiiJLr 'i '•»'••••» ' ' :•».•• .'ii rj ,i '"I'TV 'i mir-iiv!  'i™,':'	i " ',,
        ;•:;"'	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.
                                       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
          ' • '  "'!]»' ','	jli,	   . , 	,i" ; i ;• , h IJHJBIj f " I ff ,|||	 ,,. ,|,  , T , r	 Sh n n,| 	„ ,	i , i. | ,„ , |i ,,	 .
            '        had no significant negative effects on "the
                         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, ,.	 	 „	
                                                                         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
                                    Site* wtwre the weevil,
                                    has b«en rotated


                                    Ecktey Point Site

                                    C«»ar Mountain Site
                            LAKE BOMOSEEN
Figure 4. Lake Bomoseen introduction sites.
 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.

1993 1994
34 73
28 80
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
dry wt
weevils b
control sites
dry wt
"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
T!|	'""i!	l!!	Source; 's

       ,:AjltfiQUgn the conclusions
iwn from the Lake
        ^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
            Vt and" could provide a"unique management
            »!j|ij	"..SlBillJB	"Hii	-i	l,,,ii,i;;,Uiili,&,l	!!J	i,.:	:	B!t	JL.	iiiinj	«:'	.ii	,	,,,,i,,!!,i!Li,!J i ^ 	;.ja	MI	 ~	
                ' f for lakes with problems sumlar to those
                 i by Lake Bomoseen.

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Fish Lake, Wisconsin

At least three lakes in Wisconsin have
experienced EWM crashes that are believed to
be associated with the aquatic weevil
Euhrychiopsis lecontei—Devil'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 small—but
 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

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
             ! 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.
                                                                                                                	!	11	li	
                                                                                                                	|	n	pi	I	I	
        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-
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:

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