Tiny Moth Giant Threat to Florida Citrus : Agriculture: The destructive leafminer riddled last year’s summer flush, prompting the industry to form a task force to chart a battle plan. Growers are optimistic.

A microscopic Asian moth, the newest threat to Florida’s citrus industry, is puzzling scientists and worrying growers.

The citrus leafminer somehow hitchhiked into the Miami area almost a year ago and quickly established itself in much of Florida’s 790,000-acre citrus belt. Officials believe it traveled to Florida from China, Thailand or Australia in a cargo shipment or in travelers’ luggage.

The insect derives its name from its habit of boring into leaves and then “mining” them for food.

Industry leaders are scrambling to devise biological controls, since eradication is impossible. Much of the industry’s hopes rest on parasitic wasps.

Early fears that the leafminer might severely damage this year’s crop largely dissipated after the important spring flush of new foliage escaped serious damage. Growers are using expensive pesticides and special culturing methods in efforts to minimize expected attacks to new growth this summer and fall.

The destructive pest riddled last year’s summer flush, prompting industry officials to form a task force to chart a battle plan.

There was some damage to young trees, but officials said it was not extensive; however, they were unable to estimate the cost of the damage.

The leafminer’s speedy march last year through commercial groves worried many growers, according to Walter J. Kender, director of the University of Florida’s citrus research center in Lake Alfred.

“There was quite a scramble. If (the infestation) continued, we felt the important spring flush would be very vulnerable,” Kender said. “It turned out that didn’t happen, but we’re still watching it very closely.”

Scientists and agricultural experts are confident they will learn to control the leafminer, just as they have other crop-eating bugs, pests, blights and infections that have descended on groves and citrus nurseries over the years.

“Right now, we’re in a watch-and-wait period,” said Phil Stansly, entomologist at the University of Florida’s citrus research station in Immokalee. “This is one of the worst pests I’ve ever seen. But we’ll learn to live with it just as we have with the root weevil and others. . . . Most pests are under biological control.”

Five separate research projects are under way in different growing regions, and University of Florida entomologist Marjorie Hoy is in Australia to collect samples of three Asian wasps introduced to combat a leafminer infestation there. Australian researchers have found that the parasites kill about 80% of the leafminers.

Wasps, often smaller than the leafminers, lay their eggs on the body of a leafminer with larvae. When the wasp eggs hatch, they eat the miners’ larvae. Some native wasps are able to do this in a 15-day cycle.

“We feel that some wasps evolved specifically for that will do a better job than our native wasps are doing,” said Stansly. “But the natives are learning. They may have been a bigger help than we realize this spring.”

The leafminer has some other natural predators: ants, spiders and the green lacewing insect.

Growers are taking the latest threat to their livelihoods in stride.

“We’re fully apprised, totally familiar with what it can do,” said Doug Bournique, executive vice president of the Indian River Citrus League. “Right now--knock on wood--it’s not a severe problem. We have problems that have been a lot more devastating.”

Citrus industry officials say the leafminer also has shown up in five southwestern Florida counties and along the Gulf Coast.

What happens in the groves this year is the key to control, citrus extension agent Robert M. Turley said.

“Last year was a scramble to find out about it. This year, we’re a little better informed and well prepared. Once we’ve gone through a season, we’ll know how to manage it,” Turley said.

It was first discovered in May, 1993, in Homestead.

Jorge Pena, an entomologist at the Tropical Research and Education Center in Homestead, said about 3,000 acres of lime groves were quickly infested. By summer, the leafminer had traveled as far as the Florida-Georgia border.

There has been speculation that the insect was carried from West Africa by winds and ocean waves that became south Florida’s Hurricane Andrew in August, 1992. But most scientists consider that theory far-fetched.

Pena believes it’s possible that the hurricane helped spread the pest in South Florida after its arrival from foreign shores, probably aboard an ocean shipment.