January 22, 2012

Maine Gardener: New pest arrivals bode ill for Maine gardens, lawns


Three new pests could cause problems for Maine farmers and gardeners this year -- pests that arrived just last year or could arrive this year.

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The spotted wing drosophila

Courtesy photos

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The brown marmorated stink bug

Additional Photos Below

The biggest concern is the spotted wing drosophila, an Asian fruit fly that -- unlike most fruit flies -- feeds on fruit as it is ripening rather than when it is going rotten. It favors soft fruit, which includes raspberries, strawberries, blackberries, peaches and, most significant for the Maine economy, blueberries. It will eat other fruit, including tomatoes, if the skin is split.

The drosophila was found in five sites in Maine last fall, and the fear is that it could spread throughout the state.

Frank Drummond, a biology professor at the University of Maine, told the Maine Vegetable & Small Fruit Growers Association at the Maine Agricultural Trades Show earlier this month that the drosophila looks like most other fruit flies, and is only about a tenth of an inch long.

The males have black spots on their wings, but it will take a magnifying glass to see them. The females have a serrated egg-laying appendage that allows them to saw their way into fruit and deposit their eggs.

The fly is highly fecund, with each female laying about 300 eggs and the fly potentially going through 13 generations in a year. The potential of the flies spreading throughout the state quickly is high.

Although the fly was found in Hawaii in the 1980s, it did not make it to California until 2008. From there, it hit Michigan and South Carolina in 2010, and is now in all major fruit-growing areas in the U.S.

The state will be doing a trapping program for the fly this year to see where it is located in the state, but Drummond handed out sheets on how to make a trap for the flies using one-quart deli containers, insect-trapping sticky cards and a bait made from sugar, live yeast and water.

Since the fruit flies are so small, it is hard to see them and their initial damage on fruit with the naked eye. But Karen Coluzzi, a pest-management specialist with the Maine Department of Agriculture who spoke about the spotted-wing drosophila at a Board of Pesticides Control re-certification class, said that if you squeeze fruit where the eggs have been laid, juice will come out of the egg-laying holes.

The fruit flies overwinter only as adults, and Drummond and Coluzzi said there is evidence that they need winter protection from leaf litter or in buildings such as sheds to survive the winter. For that reason, berry growers are advised to clean up around their plants.

Drummond also said there is some hope that, because the pest lives through the winter only as adults, early-season berries such as strawberries and traditional early raspberries could suffer only minimal damage in Maine. But late-season blueberries and fall raspberries could suffer a lot of damage.

Drummond also said that one model of the fruit fly's potential expansion shows it arriving heavily only in coastal Maine, but that it is too soon to know if that model is accurate. Several pesticides, including one certified for use on organic gardens, will kill the spotted wing drosophila, but the time and money spent on them would be significant for commercial growers.

Coluzzi reported on another pest that has not been found in Maine yet, but is in all of the rest of the Northeast right up to the Maine boundary.

"This is a true bug, with piercing, sucking mouth parts," Coluzzi said.

The brown marmorated stink bug is both an agricultural pest and a household pest. It eats fruits, vegetables and tree leaves. Coluzzi showed pictures of severely damaged corn and tomatoes.

(Continued on page 2)

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Additional Photos

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The European crane fly

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The emerald ash borer

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The Asian longhorn beetle

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