Distribution of two European wireworms, Agriotes lineatus and A. obscurus in British Columbia

4 Pages·1997·1.8 MB·English

by  Bob Vernon

J.ENTOMOLSOC.BRIT.COLUMBIA,94,DECEMBER, 1997 59
Distribution oftwo European wireworms, Agriotes lineatus
and A, obscurus in British Columbia
BOB VERNON
PACIFICAGRI-FOODRESEARCHCENTRE,AGRICULTURE AND
AGRI-FOOD CANADA,AGASSIZ,BCVOM lAO
PEETERPATS
NORDICACADEMYFORADVANCED STUDY,
NEDREVOLLGATE 8,N-0158 OSLO,NORWAY
ABSTRACT
We determined the distribution oftwo European wireworms, Agriotes lineatus and A.
obscurus, in the Fraser Valley ofBC. Agriotes obscurus is now present in farmland
betweenDelta and Laidlaw, and the range of^. lineatus has expanded from Vancouver
Island to the lower Fraser Valley between Delta and Vancouver. The first record ofA.
obscurusinWashington StatewasmadeinLyndenin 1997.
Keywords: Wireworms,^XdXQndaQ,Agrioteslineatus, A. obscurus
INTRODUCTION
Of369 speciesandsubspeciesofwireworms(familyElateridae)foundinCanada, 194 occur
in British Columbia (Bousquet 1991). Of these, at least 27 species are associated with
agricultural land, but only eight are considered pests (Wilkinson 1963). Endemic species of
wireworms ofpotential agricultural concern in BC are: Agriotes sparsus LeConte, a pest of
potatoesinthelowerFraser Valley;Limonius canus LeConte andL. infuscatus Motschulsky,
pests of vegetables on Vancouver Island, the lower Fraser Valley, and the Okanagan and
KootenayValleys; Cteniceraaeripennis (Kirby) andC. destructor(W. J. Brown),widespread
pestsofgrainandvegetablesinBC;andC. lobata(Eschscholtz), apestofpotatoesinthelower
Fraser Valley(Wilkinson 1963).
Twoadditionalspecies,^gnoto lineatus (L.) and^. obscurus (L.),wereintroducedintoBC
fromEurope, probably around 1900, and arenow established on VancouverIsland and in the
Fraser Valley (Wilkinson 1963, 1980). These European wireworms are considered common
pestsofagriculturalcropsinEuropeandAsia(Eidt 1953), andWilkinson(1980)predictedthey
wouldbecomeseriousthreatsto agricultureinBC. Agriotes lineatuswasfirstdiscoveredinBC
nearCobbleHillon VancouverIsland (King 1950), andby 1980wasknowntohave spreadto
Vancouverinthe lowerFraserValley(Wilkinson 1980). Agriotesobscuruswasalsoreported
fromCobbleHill(King 1950),andwasfoundin 1952 attheeasternendoftheFraserValleynear
Agassiz (King et al. 1952). By 1980, A. obscurus had been reported from several farms in
Surrey(Cloverdale), about70kmwestofAgassiz (Wilkinson 1980). Sincethen, noreportsof
thedistributionof^4. obscurus orA. lineatus inBC havebeenpublished.
Inrecentyears, wireworm damage has increased dramatically in small fi^it, vegetable and
ornamental cropsthroughouttheFraserValley. ThedamageappearstohavebeencausedhyA.
obscurus or A. lineatus or both (Vernon, unpublished data) but because these species are
extremelydifficulttoidentifyusinglarvalcharacteristicsalone(Wilkinson, 1963), itisnotcertain
what species are damaging crops in certain areas. This is especially true for the Delta and
60 J.ENTOMOLSOC.BRIT.COLUMBIA,94,DECEMBER,1997
Abbotsfordregions,wherewirewormdamageto cropshasbeensevere,butneither^, obscurus
norA. lineatushasbeenpreviouslyrecorded.
Becausemosteffectiveinsecticidesforwirewormcontrolhavebeenwithdrawnfromusein
BC, alternativemanagementapproaches arebeinginvestigated. TocontrolA. obscurus inthe
Agassizregion,forexample,trapcropsforthelarvaeanddevicesformasstrappingwalkingadult
elateridbeetlesarebeingtested(Vernon,unpublisheddata). Behaviourandhostpreferenceof
differentspeciesofwirewormsvary. Consequently, differentcontrol strategiesmaybeneeded
for different species in different areas. Before deciding which methods to use to control A.
obscurus and.^. lineatus,wecheckedtheirpresentdistributionintheFraserValley,suspecting
that their ranges had expanded since Wilkinson's survey in 1963. We examined previously
collected and identified adult elaterid specimens in the collection of the Pacific Agri-Food
Research Centre (PARC) in Agassiz, and adults collected in pitfall trap surveys in 1996 and
1997. In 1996, 26 pitfall trapswere placed inthreefields in Westham Island, 33 traps intwo
fieldsinLadner(bothoftheselocationsintheMunicipalityofDeltainthe lowerFraser Valley),
20trapsinthreefieldsinAbbotsford(centralFraserValley), and6 trapsintwofieldsinAgassiz
(upper Fraser Valley). In 1997, 8 pitfall traps were established in Langley and 10 traps in
Lynden, Washington. Sub-samplesofelateridbeetlescollectedin 1996wereidentifiedtospecies
by Dr. Ed Becker at the Biosystematics laboratory in Ottawa. From these collections and
previouslypublisheddata,theknownrangesofA. lineatus andA. obscurus intheFraserValley
ofBC andnorthwestern Washington are asfollows. (Figure. 1):
Figure 1. MapofregionsoftheFraserValleyandVancouverIsland,BC, andWashingtonstate,
whereAgriotes obscurus and/or^, lineatushavesofarbeenconfirmed.
J.ENTOMOLSOC.BRIT.COLUMBIA,94,DECEMBER, 1997 61
Agriotes lineatus. CobbleHill(King 1950); Vancouver(SouthandWestVancouver, Wilkinson,
1980); Bumaby (PARC, Agassiz collection, 1980); Delta (Ladner and Westham Island, 1996
survey).
Agriotes obscurus: CobbleHill (King, 1950);Agassiz(King a/. 1952); Chilliwack (PARC,
Agassiz collection, 1953); Laidlaw (PARC, Agassiz collection, 1973); Surrey (Cloverdale,
PARC,Agassizcollection, 1973);PittMeadows(PARC,Agassizcollection, 1981); Abbotsford
(1996 survey); Delta (Ladner and Westham Island, 1996 survey); Langley (1997 survey);
WA
Lynden, (1997 survey).
Thissurveywasnotexhaustive,butdoes showthat^. lineatushasnowbecome establishedin
prime agricultural regions inDelta (Ladner and Westham Island). The highest numbers ofA.
lineatus werefoundinpitfalltrapsinLadnersurroundingapotatofieldthathadpreviouslybeen
heavily damaged by Agriotes wireworms in 1994. No A. lineatus have been found east of
Ladner in Delta. A. obscurus has been found in several locations as far west as Ladner and
WesthamIsland, andasfareastasLaidlaw. Specimens of^. obscurus were identifiedforthe
first time in Abbotsford in 1996, and in Langley, BC and Lynden, WA in 1997. Agriotes
obscurus appearstobesteadilymovingwestwardfromitsoriginaldiscovery intheupperFraser
Valley in Agassiz, andA. lineatus, now in the Fraser Valley, has moved eastward from its
hypothetical startingpointon VancouverIsland. The only region ofoverlap between the two
speciesintheFraser Valleywas inLadnerandWesthamIslandinDelta. The single specimen
ofA. obscurus caught in a pitfall trap in afield ofraspberries in Lynden is the first recorded
occurrenceofthis speciesin Washington State.
ACKNOWLEDGEMENTS
We gratefully acknowledgeE. C. Beckerforidentifyingthe 1996 collection andmany ofthe
otherspecimensofelaterids inthePARC, Agassizcollection. We also thank A.T.S. Wilkinson
for making the exceptional elaterid collection now at PARC, Agassiz, and for many usefril
discussions on wireworm identification. We thank Natalia Bassangora for providing the A.
obscurus specimenfromLynden. This is submission 565 ofthe Pacific Agri-Food Research
Centre, Agassiz,BC, andwas supported, inpart, by grantsfromEnergy,Mines andResources
(PERDprogramtoR. S. Vernon), andbythe Wenner-GrenFoundations, Sweden (toP. Pats).
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