Fruit Fly

A very tiny bug is raising big alarms for some Iowa producers. Its name is the spotted wing drosophila and it closely resembles a common fruit fly.

 It’s only an eighth of an inch long, but an infestation is now confirmed for the first time in Iowa , in Story County, with several other colonies suspected.

Laura Jesse, an entomologist at Iowa State University, says the invasive insect could be a serious threat to certain Iowa crops.

“The spotted wing drosophila is going to be a big problem primarily for small fruit growers, growers of small fruits like raspberries, strawberries, blueberries,” Jesse says.

“It can reportedly attack apples but not really fruits with harder skins.” Blackberries, cherries and grapes could also be at risk. This red-eyed pest is difficult to tell from a regular fruit fly, even for an expert on wee winged creatures like Jesse, who co-directs the I.S.U. Plant and Insect Diagnostic Clinic.

She needs a microscope to accurately distinguish the drosophila from the more common variety. “Those fruit flies, that we’re used to, attack rotting fruit,” Jesse says. “You always know when you’ve got a bunch of ’em in your kitchen, you know there’s a banana that you forgot somewhere and it’s rotten. Our normal native fruit fly can’t attack fruit that’s not damaged where as we’re concerned about this fruit fly because it can attack healthy fruit.”

The female fly can slice into the skin of fresh fruit to lay eggs and producers in other states report a serious yield impact with maggots in the produce. Jesse says the pest has already gotten a foothold in Iowa.

“Here in Story County, we were aware of it and looking for it, so we had traps out,” Jesse says. “We’ve already gotten reports at least from Mitchell County, Linn County and Dubuque County. It’s probably pretty widespread in Iowa. We’re confirming each new infestation. It’s not going to surprise us that it’ll be in a lot of counties, especially over the next few years.”

Parts of Iowa have already seen frost, but she says the fruit flies shouldn’t have a problem over-wintering in the Hawkeye State. “When it first came into the U.S, it was picked up in California, Washington and Oregon and there was some hopes that maybe it wouldn’t survive in the Midwest,” Jesse says. “It’s actually been in Michigan the past few years and done just fine there so we suspect it will be able to survive our (Iowa) winters.”

The pest is native to Asia and was first found in the U-S in 2008 and quickly spread. It’s confirmed in at least 20 states, including neighboring Wisconsin, Illinois and Minnesota. Jesse has some advice for Iowa producers with concerns about this pest: Pick all fruit when harvesting and remove and destroy any fallen, damaged and overripe fruit. Also, there are insecticides available but options are limited.

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