Where have all the stink bugs gone?

Rappahannock News - - FRONT PAGE - By John Mc­caslin Rap­pa­han­nock News staff

Yes, stink bugs re­main unwelcome guests in our Rap­pa­han­nock homes and or­chards, but the days when mil­lions of the in­va­sive in­sects raised havoc in our lives ap­pears to be wan­ing.

The ques­tion, posed with great plea­sure, is why?

Doug Pfeif­fer, a renowned Vir­ginia Tech en­to­mol­o­gist who works with the Vir­ginia Co­op­er­a­tive Ex­ten­sion Of­fice, sus­pects there are sev­eral rea­sons for the fetid bugs to be on the de­cline.

‘There are fewer th­ese past few years, and a def­i­nite de­cline since 2010. That was the big year’

There’s been progress through clas­sic bi­o­log­i­cal con­trol, pest man­age­ment with safe in­sec­ti­cides, and just maybe dis­ease is help­ing to kill off the pun­gent Asian bug­gers that first ar­rived in Penn­syl­va­nia in 1996 and in­vaded Vir­ginia in 2004.

“There are fewer th­ese past few years, and a def­i­nite de­cline since 2010. That was the big year,” Pfeif­fer tells the Rap­pa­han­nock News in a tele­phone in­ter­view from Blacks­burg. “Or­chards looked like a hail storm had come through. They’ve still been a prob­lem, but it’s not as big.”

As for the bi­o­log­i­cal war­fare Pfeif­fer refers to, Rap­pa­han­nock res­i­dents may have heard about the wasps dis­cov­ered to be par­a­sitiz­ing stink bug eggs across the bor­der in Mary­land.

“Samu­rai wasps,” Pfeif­fer iden­ti­fies them, ed­u­cat­ing that re­searchers from the U.S. De­part­ment of Agri­cul­ture had trav­eled sev­eral years ago to Asia to learn about the brown mar­morated stink bugs’ nat­u­ral en­e­mies. The thought was to in­tro­duce a bio­con­trol species or two in North Amer­ica, where hun­dreds of mil­lions of dol­lars in crop dam­age was oc­cur­ring an­nu­ally, in­clud­ing in Vir­ginia’s ap­ple or­chards.

While some of the so­called samu­rai wasps (Tris­sol­cus japon­i­cus) were even­tu­ally brought to Amer­ica to study in the lab en­vi­ron­ment, to every­body’s sur­prise they were re­cently dis­cov­ered to al­ready be liv­ing here. Iden­ti­fied by Mary­land re­searchers, th­ese tiny wasps had im­mi­grated to the mid-At­lantic states on their own, so small in size (no big­ger than a sesame seed) they were hardly no­ticed. Not to men­tion they can’t sting.

“Of­ten when we search for nat­u­ral en­e­mies we go back to the home­land to look for the pest . . . find what works well in the home coun­try,” Pfeif­fer ex­plains. “Of course th­ese ‘en­e­mies’ have to un­dergo test­ing” to pre­vent any ad­verse ef­fects on the lo­cal en­vi­ron­ment, “to make sure they’re preda­tory in­stead of plant feed­ing.”

“No­body knows how it got here,” the en­to­mol­o­gist says of the U.S. samu­rai dis­cov­ered first in Delaware, al­though re­searchers are con­vinced they didn’t es­cape their sci­en­tific quar­an­tine. Now, as we speak, ad­di­tional wasps are be­ing re­leased in fields and or­chards up and down the east coast.

“It’s un­clear how much of an im­pact the wasp is hav­ing,” says Pfeif­fer, but every­body is hop­ing for some progress.

The Tech pro­fes­sor says there may be other “nat­u­ral en­e­mies” to stink bugs that in­crease its mor­tal­ity, in­clud­ing dis­ease. Plus, he says, fruit grow­ers “are more aware of how to han­dle” the in­va­sive pests, from safe in­sec­ti­cides to traps placed on trees.

Pfeif­fer also pointed to re­search con­ducted in his own lab for short term pest con­trol, where for in­stance “on the night be­fore a grape har­vest an or­ganic in­sec­ti­cide blasts the bugs out of the clus­ters.

“The is­sue is less with grape grow­ers, but we do pro­vide an­other tool,” he says.

Stink bugs feed on nu­mer­ous fruits and veg­eta­bles, from ap­ples and peaches to toma­toes and sweet corn. For or­chard grow­ers and farm­ers a plen­ti­ful army of stink bugs can wipe out an en­tire sea­son’s har­vest.

For home­own­ers, they are a nui­sance pest as they look for places to over-win­ter. Hope­fully this win­ter of 2018-19 there won’t be as many swim­ming in our soup.

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