Growers told of wasp that may aid battle against squash bugs

Staff Reporter

PAINTER, Va. (July 15, 2014) — Virginia growers battling squash bugs should be on the lookout for a parasitoid wasp discovered in the state last year that is particularly effective at fighting against the notorious produce pests, Virginia Tech researchers said last week.
The wasp, Groon pennsylvanicum, lays its eggs inside squash bug eggs typically attached to the underside of the host plant’s leaves, said James Wilson, a doctoral student in the university’s entomology department who discovered the wasp in Blacksburg last year while studying squash bug nymphs.
Wilson has been under working entomology professor Tom Kuhar, who presented the discovery during the university’s annual field day at its Eastern Shore Agricultural Research and Extension Center on Wednesday, July 9.
“It’s an added beneficial,” Wilson said. “With a little closer look, we might be able to find that we’re getting a little helping hand from the wasp.”
Farmers spraying insecticide to stop squash bugs should wait until nymphs hatch, Wilson said. Spraying before that could kill the wasps, and the nymphs are less likely to be exposed to the insecticide inside their shells.
In a pumpkin field at the university’s Kentland Farm, Wilson discovered wasp parasitism in 82 percent of 84 collected squash bug egg masses. About 66 percent of all eggs collected were parasitized, according to Wilson’s report.
The relationship between the wasp and squash bug eggs has been studied and reported in other states, including Kentucky and North Carolina. But researchers were unaware of the wasp’s presence in Virginia until last year, he said.
Wilson and Kuhar said they plan to survey growers, large and small, across the state to better determine how far these wasps have spread and to how feasible it might be deploy them on farms with squash bug issues.
The wasps were recently introduced into some Italian farms to control an insect that kills immature pinecones, a threat to the country’s pine nut industry.
Squash bugs feed on cucurbits, including squash, pumpkin and zucchini. The insects’ saliva is toxic to the plant, and their leaves can wilt and die after feeding. Significant foliage loss can cut the flow of nutrients to the larger fruit, and squash bugs may also carry a bacterium that causes Yellow Vine Decline.
“It will eventually take out most squash if you don’t take it out,” Kuhar said.
But the discovery may mean good news for squash growers in Virginia.
“It could be something new that’s starting to spread,” Kuhar said. “It could mean just because you see eggs doesn’t mean you’re going to get these squash bug nymphs.”