FRESNO, Calif. — It was not what grower-shippers wanted to hear.

Three years after the light brown apple moth was first discovered in North America — in the San Francisco Bay Area — scientists from the U.S. Department of Agriculture and the California Department of Food and Agriculture have not found the answer to eradicate the pest.

The two agencies are working with colleagues in other countries on several approaches, Gregory Simmons, the supervisory agriculturist for the USDA’s new laboratory in Moss Landing, told a workshop Feb. 23 at the Reedley-based California Tree Fruit Agreement’s annual education symposium in Fresno.

Scientists make little progress on LBAM solution

Simmons

A concern is that there are so many hosts for the moth, known in California as LBAM. Nurseries are a top concern, Simmons said.

“They are a major pathway for the LBAM to move around,” he said.

A female moth can lay several hundred eggs, and the egg mass is difficult to spot. In the California climate, there can be as many as four generations of LBAM annually, Simmons said, and the number of discoveries in traps is increasing. While scientists believe they know the damage the apple moth can do, invasive pests can be something of a mystery, he said.

“We don’t really know what they’re going to do when they get here,” Simmons said. “They may cause many problems. They may putter along and do nothing.”

The initial plan in 2007 was to eradicate the apple moth population in California. After residents of several communities and environmental groups went to court to block the use of pesticides, the technical working group decided to base its long-term strategy for the control and possible eradication of LBAM on a variety of methods, Simmons said.

Those methods include the use of pheromones, natural predators and sterile moth releases, he said.

All of those approaches are being tested and evaluated in this country and in other countries as is the strategy itself, Simmons said.

“One tiny wasp native to North America has performed well,” he said.

The scientists also are evaluating at least one natural enemy found in Australia.

Because the LBAM does not have an overwintering resting stage and must survive winters in one of its forms, Simmons said it may not survive in colder climates. Tests have been performed on LBAM infested strawberry plants, he said, that are placed in cold storage for four weeks.

“We found that cold treatment works at 28 degrees,” Simmons said. “There aren’t any stages of the LBAM that will survive.”

Distributing sterile moths into infested areas to try to suppress the field population is the approach on which Simmons’s research is focused.

“It’s a tool that’s been effective in controlling or eradicating a number of invasive pests, such as the pink boll worm and a number of fruit fly species,” he said. “In effect, we’re using the biology of LBAM against itself.”

When used in combination with pesticides, pheromone baits laced with small amounts of a pesticide, the sterile moth approach can put great pressure on the pest population, Simmons said.

The Moss Landing laboratory is now producing 1 million LBAM eggs weekly to be sterilized via radiation and released. The first full season of testing and evaluating will begin in April, Simmons said.