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Light-brown apple moths: California deploys wasps as weapon

July 5, 2011 |  2:57 pm

Photo: The light-brown apple moth Credit: California Department of Food and Agriculture The insatiable fruit- and leaf-eating light-brown apple moth may meet its match this month as California prepares to release hundreds of tiny, stingerless wasps. The move is part of a continuing effort to move away from aerial pesticide spraying to eradicate pests.

The California Department of Food and Agriculture will deploy the stingerless wasps, which are native to California, in San Luis Obispo and Sacramento counties. The wasps, no bigger than a grain of rice, will lay their eggs inside of light-brown apple moth eggs. When the wasp larvae emerge, they kill developing moths.

“These tiny wasps are harmless to people and pets, but they have a big appetite for the eggs of light-brown apple moths,” said California Agriculture Secretary Karen Ross, adding that the "integrated pest management approach" minimizes detrimental effects.

Asael Sala, a community organizer for Pesticide Watch, a Sacramento-based organization that promotes sustainable pest control, praised the state's approach. “Stingerless wasps are an important part of ... green pesticide practices,” Sala said. "We’re definitely glad to see that continuing.”

The light-brown apple moth is native to Australia and damages crops, trees and plants in both rural and urban areas. California is the only known infested area in the U.S.

Eradicating the light-brown apple moth from 15 counties in California, including Los Angeles, began in 2007, when the species first appeared in Monterey and Santa Cruz. Agricultural officials quarantined infested crops and sprayed pheromones mixed with water. Pheromones confused the male moths, disrupting the mating process, allowing the population to die out.

At the time, the agency acted under emergency provisions in the California Environmental Quality Act, which allows it to conduct an environmental impact report concurrently rather than before spraying, to assess how pesticides would affect the area.[clarification: an earlier version of the post said the agency was exempted from issuing the report.]

Impact statements "can take one year-plus, and if you wait, you lose your window to take out the pest,” said Steve Lyle, an agency spokesman. “The moth would have been so firmly established, it would have been very difficult to remove it.”

Within a month, dozens of residents complained to local health officials of illnesses they thought were connected to the spraying, but no definitive link has been made. And two courts ruled that the agency had no grounds for an emergency program.

The agency's 2010 impact report determined that it was unlikely that the approaches in the moth program would cause human harm or environmental damage, however officials turned to new strategies. Those included moth sterilization, pheromone-releasing twist ties on plants and, now, stingerless wasps.

In Sacramento and San Luis Obispo, crews will place small cards with the wasp pupae on outdoor plants in the infested neighborhoods. Residents will be contacted individually by crews as the wasp cards are placed. “If somebody had a serious reservation, we’d talk with them to see how we could work with them,” Lyle said.

The new strategies of twist ties and wasps are being applied in counties with small moth infestations. However, the goal is to extend the new methods to larger affected areas such as San Francisco Bay.

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--Ashlie Rodriguez

Photo: The light-brown apple moth Credit: California Department of Food and Agriculture