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UH team warns of invasive pests burrowing in isles


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POSTED: Monday, December 01, 2008

Many Hawaii nurseries are infested with alien snails and slugs, potentially serious pests that harm agriculture and the environment, four University of Hawaii-Manoa scientists report.

In an article published in the October-December International Journal of Pest Management, biologists Robert H. Cowie, Kenneth A. Hayes, Chuong T. Tran and Wallace M. Meyer III express concern about widespread invasions of alien snails and slugs in the isle horticultural industry.

Most worrisome, the creatures might be hitchhiking aboard native Hawaiian plants that are part of the vegetation restoration program for Kahoolawe and other damaged Hawaii ecosystems.

Snails and slugs are all gastropods, a subdivision of mollusks. Slugs are snails that have lost their shells through the evolution process, said Cowie, chairman of the Ecology, Evolution and Conservation Biology graduate program.

The snail and slug specialists are in the UH Center for Conservation Research and Training in the Pacific Biosciences Research Center. They documented the distribution of snail and slug species associated with Hawaii's horticultural industry for the first time, surveying 40 nurseries on the major islands.

They found alien snails and slugs in all of them.

The collection included 29 alien species—five of which had never been reported in Hawaii, Cowie said in an interview. Many species also were found on particular islands where they had not been spotted before, he said.

The nurseries each had from one to 17 invasive species, even though some said they had none.

“;We asked, 'Do you mind if we have a look?' and we always found something,”; Cowie said. “;Our main concern was the fact that there's a whole bunch of snails and slug species much smaller than most people are aware of, and a lot of nurseries are infested with these things and didn't know they had them.

“;Because they didn't know they had them, they're shipping them all over the place, to other islands and out of state.”;

One alien species is often found in garden stores supplied by nurseries, “;which is of particular concern in nurseries that are supplying native Hawaiian plants for restoration of damaged Hawaiian ecosystems,”; the biologists said.

For instance, plants being supplied by some nurseries to restore native habitats on Kahoolawe are infested with non-native snails, Cowie noted.

The environmental impact of the introduced invasive species is not known but could be severe, the scientists said, emphasizing the need for greater awareness of the snails and vigilance in detecting them in the nurseries and shipments from local and overseas nurseries.

From the pattern of distribution among the nurseries, Cowie said it is believed the pests came into Oahu originally, escaped around the island and were transported to the other islands through horticultural traffic.

“;It would be really worthwhile to study the patterns of imports and distribution networks around the islands that the horticultural industry uses,”; he said. “;It would allow us conceivably to put controls at certain key points. Entry into the state is an obvious key point.”;

Cowie said the state Department of Agriculture “;does a sterling job, but it can only do so much with limited manpower and you have to know what you're looking for. Some (slugs) are pretty small.”;

Probably the best thing a nursery can do to prevent snails and slugs from becoming abundant is to “;make sure they're clean and tidy and don't use plastic sheeting as mulch,”; he said. “;Slugs love to live under it.”;