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Researchers fear setback in moth fight

Hurricane Katrina might have harmed work to stop the cactus moth from moving west.

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PENSACOLA - The cactus moth was hailed in the 1920s for stopping the prickly pear cactus from overrunning the Australian Outback, where the spiny plant had been imported from its native South America as a natural cattle fencing but got out of hand.

Cactoblastis cactorium 's success as a biological pest control, however, has boomeranged. The insect later was used against prickly pear in other places, including the Caribbean. It was just a short hop to the Florida Keys in 1989 and then mainland North America.

Scientists now are trying to stop the gray brown moth from advancing along the Gulf Coast to the Southwest and Mexico, where it could wreak havoc on cactus vital to agriculture, horticulture and the environment.

They have drawn a line in the Florida Panhandle and Alabama, where two experimental methods are being field-tested, but Hurricane Katrina may have dealt them a setback last week when it battered Dauphin Island near Mobile, Ala.

The moths, which consume cactus in the caterpillar stage, will be much harder to stop if they can cross less than 10 miles of the Gulf of Mexico to Mississippi's Petit Bois Island. It has plenty of cactus and is accessible only by boat, said Jim Carpenter, a research entomologist with the U.S. Department of Agriculture in Tifton, Ga.

Adult moths from the latest generation apparently were no longer flying around when the storm hit, none had been caught in traps recently, but scientists are worried Katrina may have broken off cactus pads infested with caterpillars and scattered them into the gulf.

Currents might wash the pads ashore farther west, where the caterpillars then would produce another adult generation this fall, said Stephen Hight, a USDA research entomologist in Tallahassee.

The USDA's Agriculture Research Service in April began releasing tens of thousands of sterile male moths on Dauphin Island to mate with wild females so they produce only infertile eggs.

Researchers also have physically removed infected cactus pads and plants or simply picked off white cocoons, the red orange and black-spotted caterpillars and eggs laid in sticks that resemble cactus spines.

This approach on Dauphin Island and eastern Santa Rosa Island near Fort Walton Beach in the Panhandle is an alternative to insecticides that have proven ineffective, Hight said.

At stake is what USDA estimates is a $70-million U.S. prickly pear industry, mostly in the Southwest, where cactus is used for landscaping and forage.

In Mexico, people also eat prickly pear fruit, often boiled or pickled. The industry there is valued at $50-million to $100-million.

In nature, cactus prevents soil erosion and provides food for birds and wildlife.

Sterile moths are being released when the insects mate in April-May, July-August and October-November. Another release is planned next spring. Data then will be analyzed before deciding whether to implement one or both control methods or neither, Hight said.

Sterile insect releases have succeeded against such pests as the Mediterranean fruit fly, which ruins citrus crops. That method also has worked with two other moth species that attacked cotton in California and apples in British Columbia, Canada.

The cactus moth poses a more difficult problem in part because it infests a wild plant rather than one that grows only on farms or in orchards. "It is difficult to find where all the cactuses are growing," Carpenter said.

Meanwhile, the hurricanes so far have had one positive effect by encouraging property owners to let researchers remove storm-damaged cactus.

"The plants were just gnarly, messed up," Hight said. "So, people were glad to get them out of there."

[Last modified September 6, 2005, 03:15:21]