California will begin releasing sterile light brown apple moth (LBAM) larvae early next year as yet another tool that California Department of Food and Agriculture (CDFA) and USDA officials hope will eradicate the voracious pest from the state.

Photo by David Williams, State of Victoria Department of Primary Industries.

It is the same technology used to eradicate the Mediterranean fruit fly from three California counties earlier this year. The technology was developed more than 40 years ago by USDA-ARS to rid the U.S. of a flesh eating larvae called the screwworm.

Sterile moth releases also have excluded the pink bollworm from becoming a pest of California cotton for 40 years.

Larvae are scientifically mass reared and then sterilized. When released, sterile insects then mate with any native pests with the result being nonviable eggs.

Robert Dowell, CDFA director of the LBAM eradication effort, told the California Association of Pest Control Advisers (CAPCA) annual conference in Anaheim, Calif., that the first shipment of 500,000 sterile larvae are expected to be released early next year within quarantined areas of the state where the LBAM has been trapped.

Since its detection in February 2007, the LBAM has been found and quarantines have been enacted in Monterey, Santa Barbara, Santa Cruz, Santa Clara, San Mateo, Contra Costa, Marin, San Francisco, Alameda, and Solano counties. Small, isolated infestations detected last year in Los Angeles and Napa counties have already been eradicated. Pheromone impregnated twist ties were utilized in both counties to disrupt mating in the small population that was detected.

Sterile LBAM are being reared in the same facility in Phoenix where the state of California and California cotton growers rear and sterilize pink bollworms which have been utilized for four decades to keep pink bollworm from becoming a pest in San Joaquin Valley cotton.

Although this technology has been proven in agriculture, Dowell said the LBAM sterile project will be a pilot program initially. “This technology will be more challenging in an urban environment” than an agricultural environment since there are multiple generations of LBAMs in populations feeding on a wide array of host plants. This makes it challenging to reduce populations by releasing sterile insects.

Nevertheless, Dowell hopes it is successful and by 2010, 20 million moths per day will be released into infested areas to aid in eradicating the pest.

Typically, it takes three to five years to perfect a sterile release program for a new lepidopterous pest. However, thanks to an accelerated effort from scientists associated with the PBW rearing and release program as well as researchers from Hawaii, New Zealand and Australia where there are LBAM infestations, the technology has been perfected for LBAM in less than two years.

The facility in Phoenix also provides sterile PBW used in an ongoing, successful effort to rid Mexico, Arizona, New Mexico and Far West Texas of PBW.

While the PBW and screwworm larvae are specific in their targets, LBAM has been dubbed the “light brown everything moth” because more than 2,000 plants have been identified as hosts, most of them ornamental plants.

A USDA study indicates that if California becomes generally infested, the moth could cause billions of dollars in crop damage annually.

Additionally, Dowell said if allowed to spread uncontrolled, California food and ornamental exports could be under a “perpetual quarantine” that could cost billions in lost export and domestic sales.

Quarantines have already been enacted by Canada and Mexico. California agricultural exports to the two countries totaled more than $2.4 billion in 2006.

“Quarantines are real, not hypothetical. They will not go away,” Dowell says. “There are people who say all we have to do is tell other countries and states that California made a mistake and has a problem, but ‘won’t you please be so kind and not quarantine us’ and they won’t.”

“People who say that also believe in the tooth fairy,” he says.

LBAM is a leafroller that breeds continuously and has no diapauses. CDFA catches it in 40,000 traps 52 weeks per year. Between 2007 and 2008, populations doubled in Santa Cruz County and increased fivefold in San Mateo and San Francisco counties and sevenfold in Marin County.

It is native to Australia and likely made its way into California on nursery stocks.

So far it has been isolated along California’s coast. It has heavily damaged forest and landscape plants and has been found in grapes and berries in commercial agriculture.

Dowell said along with the fears of quarantines limiting shipments of California food and ornamental products, his biggest concern is that the pesticide load will increase in California unless the pest is eradicated. Most of this new pesticide load will likely come from homeowner use of pesticides.

Dowell said the use of permethrin would increase by 4,000 pounds from San Diego to Mendocino if LBAM becomes permanently established.

“Two-thirds of homeowners do not read labels; two-thirds do not know how to measure when mixing pesticides and 20 percent pour unused pesticide into urban wastewater. We do not need a couple tons of (more) material put into the California environment.”

He also listed an array of products that would be used in agriculture to control the new leafroller pest. Most would increase by double figures if the LBAM becomes established in the central San Joaquin Valley. It would cost the Valley billions of dollars if LBAM becomes established in the heart of California’s $30 billion agriculture industry.

Dowell admitted the exotic pest continues to spread despite federal and state efforts to stop it.

However, he and the technical working group evaluating the pest and control measures believe it can be eradicated. The infestation is still “relatively small and discrete,” Dowell explains.

The state is utilizing an array of pheromone mating disrupting techniques using ties and other pheromone carriers. CDFA also is utilizing pheromone attract-and-kill technology as well as parasitic wasps.

Surprisingly, the aerial application of mating disruption material has been the most controversial.

“I guess we were a little naive when we thought people, given the choice of treating with Bt, spinosid, or malathion, would prefer pheromones,” Dowell said. However, CDFA has been challenged in court as well as in the Legislature for its aerial application of pheromones, and mating disruption products can now be aerially applied only in uninhabited areas.

Despite all the controversy swirling about LBAM, Dowell says eradication is the best option.

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