Fruit Fly – Tiny pest threatens local fruit crops

A new pest soon will be bugging Centre County’s fruit growers.

The spotted wing drosophila, an Asian fruit fly, has been sighted throughout Pennsylvania and along the East Coast.

In larger numbers, it has the potential to eat its way through high-value fruit crops, such as blackberries, raspberries, blueberries and grapes, according to Kathy Demchak, a senior extension associate with Penn State’s department of horticulture.

“I’ve never seen anything spread quite this rapidly,” Demchak said. “We’re just crossing our fingers and trying to hang on until we have a better idea of how to manage it.”

The spotted wing drosophila, a fruit fly native of Japan, landed in California in 2008. By 2009, swarms of the bug had ruined billions of dollars of crops on farms from California to British Columbia, Canada.

Two of the pest’s traits make it particularly dangerous to fruit growers. Instead of targeting ripe fruit exclusively, the drosophila deposits eggs under the skin of unripe fruit as well. Its rapid regeneration rates mean it can reproduce up to a dozen times in a season, with each female producing 250 to 300 offspring per mating cycle.

Complicating matters is that the spotted wing drosophila is not a regulated pest in food transportation, so there has been no way to stop infested fruit from coming into Pennsylvania, Demchak said.

The drosophila fruit fly was first identified in large numbers in Florida in 2010, and has made its way up the East Coast this year. Because it didn’t arrive until later in the season, next year could be the first where Pennsylvania sees the full brunt of its impact.

“It doesn’t love cold temperatures, so we’re not sure how it winters,” Demchak said. “Because we don’t have a whole lot of experience with this species of fruit fly, we don’t know what populations we’re going to start out with next year.”

Organic farmers and pick-your- own operations are at the greatest risk, Demchak said.

“One good thing is that it is a fruit fly that can be controlled with chemical sprays if need be,” she said. “But the concern we have with some of those sprays is that they do create a heavier impact on the environment.”

Greg Krawczyk, a senior research associate in Penn State’s department of entymology, said growers of fruit such as peach, nectarines, berries, grapes, cherries and some types of apples and pears should learn more about the drosophila, and keep an eye out for it in their fields.

“It’s something that might be very, very dangerous to them,” Krawcyzk said.

Because of its small size, it’s difficult to spot the bug’s trademark spots on its wings, and a growth in the population of the spotted wing drosophila may be disguised by a surge in the fruit fly population in Pennsylvania this year.

“Although we haven’t seen too much of an impact yet in Pennsylvania, the drosophila fruit fly have been spotted in pretty much every county, and this state has an environment that’s very conducive to them,” Demchak said.

Jason Coopey, the co-owner of Way Fruit Farm in Port Matilda, said he has seen one or two of the spotted wing drosophila but had not yet discovered any damage to his crops.

“It’s not on our mind at this point,” he said. “It’s one of those things … last year, there was the brown marmorated stink bug, and we haven’t really had a problem with that. But of course, things could change.”

Coopey said the farm would use pesticides as a last-ditch measure only.

“We are willing to take some damage in order to keep our pesticide use low,” he said. “Realistically, until we have a huge problem we won’t treat (our fruit.)”

Cliff White can be reached at 235-3928.

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