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

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.

When the weather gets colder, it will try to invade homes — which is a big problem because, as its name suggests, the bug stinks.

Maine has other stink bugs, but those do not do much, if any, damage to crops. And while the marmorated stink bug does not kill the crops it eats, and doesn’t even make it totally inedible, it does cause enough damage to make the crops unmarketable.

The brown marmorated stink bug has an alternating black-and-white edging on its shield-shaped back and alternating black and white antennae.

The third new pest damages lawns only, and so far has been found only on Mount Desert Island. The European crane fly is also called the leatherjacket, and as an adult it looks like a huge mosquito, measuring 1.5 inches long, similar to other native insects.

The adults do no damage, but often will try to get inside people’s houses, and can be a bit scary-looking, Coluzzi said. But the larvae will eat both the roots and new shoots of grass, doing damage similar to that done by the European chafer.

The emerald ash borer is old news, although it has yet to arrive in Maine. It has decimated the ash trees in Michigan, and is now as close as the Hudson River Valley.

The emerald ash borer travels mostly on firewood, so the state is not allowing people to bring firewood into Maine, and is urging people not to transfer firewood around Maine. The borer tunnels through the cambium layer of ash trees and kills them quickly.

The state will increase its monitoring for the emerald ash borer from 200 traps last year to 1,000 traps this year in an effort to locate the pest as soon as it arrives. The prism traps are purple, but they give off the same light wavelength as ash leaves, so are attractive to the borer. So don’t be surprised if you see the traps while traveling through the woods.

The Asian longhorn beetle is another pest that is as close as Worcester, Mass., but has not arrived in Maine yet. This pest can be controlled if it is caught early. It is a large beetle with long horns, so if you see one, contact the Department of Agriculture or the University of Maine Cooperative Extension.


Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth and can be contacted at 767-2297 or at:

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