Wasp attacks worsen
European PaperWasp themain villain as damage reported in orchards and vineyards.
By Scott Trudeau A
longtimewinery owner in Okanagan Falls says the European PaperWasp ravaged
his grapes last summer attacking his vineyards in record numbers. LarryGerelus, of Stag’sHollow
Winery and Vineyardwas surprised by the numbers
ofwasps.Gerelus said he’s never seen anything close to it during the nearly two decades he’s been operating hiswinery. Gerelus first noticed thewasps among
hisMuscat grapes,which ripen earlier than others. “Oncewe knewitwas happeningwe
sawbasically the numbers build,” he said. “Normallywe don’t see that kind ofwasp pressure at all. Ifwe do see some it’s a non-issue.We have put traps out in the past but this year,we had to,
to try and capture asmany of thewasps aswe could.” In previous years, homemade traps
constructed fromtwo-litre pop bottles were placed among his PinotNoir grapes,where thewasps had been prevalent. “We’d catch a decent number,” he
said. “There’s alwayswasps around. The amount of damagewasn’t significant enough toworry about in the past.” Last summer,Gerelus said “it became worrisome”with regards to the volume
European Paper Wasp
ofwasps attacking his grapes and that there is “definitely a dollar value to the damage.” He began purchasing traps after
realizing they couldn’t keep up to the number ofwasps.He bought about a dozen traps but theyweren’t near enough to keep capturing the swarms landing on his grape clusters. When he returned to the store to
purchasemore theywere sold out. “So obviously the problemwaswidespread.” The attacks continued through
August and into September and October,with the greatest damage occurringMuscat, PinotNoir and Tempranillo varietals, compared to Merlot and Vidalwhich received far less damage. Horticultural consultantDuane
Holder said the European PaperWasps have been a problemsince about 2008. “The European PaperWasp has been
themost serious species that’s attacked cherries,” he said. “It became a problem for some of the orchards in the Creston area but also some of the orchards in theOkanagan have been affected by it —and I knowgrape growers have had issueswith it too.” Weather plays an important part in
the number of European PaperWasps. “The queens,when they emerge in
SCOTT TRUDEAU
Stag’s Hollow Winery and Vineyard in Okanagan Falls, shown here in mid-February, was attacked by the European Paper Wasp in record numbers last summer. Wasp traps were relatively ineffective at controlling the invader. Inset photo of grape bunch illustrates the high number of wasps that were responsible for destroying a significant number of grapes at Stag’s Hollow.
the spring, start to build nests and if spring conditions are fairlywarmthey get off to a good start,whereas if the conditions are cold andwet it probably inhibits their population growth a little bit,” saidHolder. “When you get into a hot, dry summer, especially an early seasonwhere they can go throughmore expansion of their population then they
British Columbia FRUIT GROWER • Spring 2014 21
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