Sunday, September 16, 2001

Slug research could save farmers money

Study focuses on parasite that can kill crop-eating pests

By Andy Resnik
The Associated Press

        COLUMBUS — Ohio State University researcher Parwinder Grewal hopes his latest project moves along quicker than the pace of his subjects: slugs.

        Mr. Grewal, an entomologist, has spent two years examining and dissecting slugs. He's looking for a small parasitic worm known as a nematode that crawls into a slug through its breathing pore, multiplies and kills the pest in about a week — hopefully before it eats valuable plants and crops.

        “Last year in Ohio, because of the good rains we had in the summer, slug populations were so high that some farmers had actually lost their entire corn crop,” Mr. Grewal said.

        He said slugs mainly eat plant leaves, but if weather conditions are right, they can consume an entire plant just as it starts to grow.

        David Graham, a Wayne County farmer who has about 1,000 acres of corn and soybeans, said he has had entire fields wiped out in three to five days.

        “You can still make a profit if you can get in there and get it treated,” Mr. Graham said. “If you don't, you'll be wiped out.”

        Ron Hammond, an OSU field crop entomologist, said slugs have always been a problem, but do more damage on no-till farms.

        No-till leaves residue on the soil surface to protect against erosion, but also leaves enough moisture in the soil to sustain slugs.

European variety

        Mr. Grewal said farmers' problems could be solved by a nematode that has been found in England and is being mass-produced to control slugs in Europe.

        If Mr. Grewal could find that nematode in a North American slug, it could be used in the United States. He said he may also find another nematode that is native to North America and works as effectively as the European nematode.

        Mr. Grewal said he has isolated 20 nematodes from the roughly 20,000 slugs he has examined, but has not found the nematode being used in Europe.

        He has received a permit that's allowed him to use the European nematode for experiments. He says it's been effective against the most common slug pest — the gray garden slug — but can't be used commercially because of government regulations.

        In one experiment, Mr. Grewal treated 12 gray garden slugs with the nematode and then put the slugs into a tub with four hosta plants. The nematode kept slugs off the plants for eight to 10 weeks, he said.

        In experiments on six other slug species, the nematode didn't kill the slugs but stopped the pests from eating the plants, he said.

        Mr. Grewal is uncertain how long his research will continue. If he can't find the European nematode here, he plans to ask the federal government to consider approving its use in this country.

        The U.S. Environmental Protection Agency and the U.S. Department of Agriculture would have to be certain the European nematode wouldn't harm the environment before it could be used in the United States, said David Chitwood, a research leader in the nematology laboratory at the Beltsville Agricultural Center in Beltsville, Md. The center is part of the USDA.

        “If you're using a nematode that's already found in Ohio, for instance, that's probably going to be a bit more favorable for regulatory agencies than something from England, when you have to worry what other hosts it might have,” Mr. Chitwood said.

Toxic bait

        Currently, farmers fight slugs with metaldehyde, a toxic bait that lasts 10 days to two weeks in dry weather, Mr. Graham said.

        The metaldehyde comes in pellets that cost $1.65 to $1.90 per acre. With 10 pounds needed for each acre on his farm west of Wooster, Mr. Graham estimates he has spent about $6,000 this year on killing slugs.

        He also spends several hours a week looking for the white slime and bite marks the slugs leave behind.

        “Anything that's cheaper and better is fine with me, but they can't spend 10 years working on it,” Mr. Graham said. “I won't be in business by then.”

Mail-order vermin

        Without help from farmers like Mr. Graham, Mr. Grewal wouldn't have been able to do his research at OSU's agricultural labs in Wooster.

        Mr. Grewal got extension agents in Ohio to tell farmers to ship him slugs and also placed ads in garden magazines, hoping greenthumbs from across the country would mail him slugs from their greenhouses.

        He ended up with about 20,000. Most were sent in margarine tubs with air holes that allowed the slugs to breathe.


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