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Invasive Fruit Fly Threatens Maine Berry Crops
10/05/2012   Reported By: Patty B. Wight

A new, tiny insect in Maine - even tinier than a baby's fingernail - has the potential to wreak huge havoc on the state's berry growers. The Asian spotted winged fruit fly can turn perfect fruit into a gooey mess in a matter of days. The fly first arrived in the western U.S. three years ago. Last year, it made its way to Maine. Its numbers have grown so quickly it has agricultural experts scrambling to find a way to minimize the damage to commercial berry crops. Patty Wight has more.

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Invasive Fruit Fly Threatens Maine Berry Crops Listen
 Duration:
3:25

Fruit fly 1

Three days a week, David Handley, a small fruit specialist for the University of Maine Cooperative Extension, and crop technician Katie Woodman cross the state in a bright blue truck to check fruit fly traps (left). They know the spotted wing fruit fly is here - now they want to find out how the population fluctuates, so they can better predict when and how farmers should manage them.

The first stop this day is Chipman Farm in Dry Mills. Handley and Woodman drive across a field to a trap adjacent to a row of raspberries. "We'll show you our high tech equipment here," he says. "And it's just sitting here on a tomato stake - a wooden six-foot tall wooden tomato stake - and we've screwed a ring clamp into it."

The clamp holds a red plastic cup - the fruit flies are attracted to the color red, as well as what's inside: a mix of apple cider vinegar, white grape juice, and a little alcohol to help disperse the odor. "It basically smells like ripening or slightly overripe fruit," Handley says.

Handley lifts the lid to a vinegary brew of mostly spotted wing fruit fly, with a few unlucky houseflies mixed in. Katie Woodman estimates there are about 200 spotted fruit flies in the trap, but she's seen far more. "We've had thousands at this site," she says.

Patty Wight: "In one cup?"

Katie Woodman: "In one cup, yes."

David Handley: "Over one week - that's one week's worth of catch."

Handley says there are two things that are particularly troubling about the spotted wing fruit fly. First, its ability to reproduce.

"So each one of these little flies can lay up to 300 eggs," he says. "And it only takes them, on a good stretch of weather - 14 days - to go from egg to another egg-laying adult. So you can see how the population can go from just a few flies to millions in just a matter of a couple of weeks."

Fruit fly 2The other thing that makes these fruit flies troubling is a specialized tool used by the females: saw-like ovipositors, which they use to deposit eggs. Whereas regular fruit flies are attracted to rotten fruit, the spotted wing females like unripe fruit because their ovipositor can easily cut through fruit's skin to lay eggs.

The affected fruit can look perfectly fine on the outside, but inside it's filled with larvae. And this presents a conundrum to small berry growers: to spray, or not to spray? Because some consumers want their food local, but without the pesticides.

"We've put some investment into some equipment that people probably don't like - we put a new sprayer in," says Walter Goss, who owns a berry farm in Mechanic Falls. He says the sprayer was an expensive investment - the price of a new car - plus he spent an extra $1,000 on insecticide for weekly treatments.

But it was either spray or lose his crops, he says. "This is our livelihood, this is what we do. We only grow raspberries and blueberries, and I can't let it take over. Otherwise I'm out of business."

drosophilaBut smaller berry growers may not have the resources to buy this kind of equipment to treat their crops. David Handley from the Cooperative Extension says he, along with others around the country, are working to find other ways to manage the spotted wing fruit fly.

He wants to improve their traps so they'll catch the spotted wing fruit fly (left) earlier in the season, when there's more time for farmers to respond. He says they're also looking for a biological parasite that will attack the fruit fly. But for the forseeable future, he says, spraying will be necessary.

"This to me is going to be a major investment for farmers in the future," Handley says. "It's not something that I think is going to go away, based on what I know about it already. And we are always going to have to be dealing with it from now on."

Click here to learn more about the spotted fruitfly, drosophila.

Photos of David Handley and Katie Woodman by Patty Wight.



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