Invading moth damages berries; quarantines grow

Issue Date: June 17, 2009

By Kate Campbell
Assistant Editor

Extensive damage to blackberries grown on a Santa Cruz County farm, as well as rapidly expanding pest quarantines in other counties, have heightened concerns about light brown apple moth infestations in California.

Right now more than 3,000 square miles are under federal quarantine to restrict the spread of this invasive, non-native pest while government officials work to contain and control its spread. The impact of the infestations and quarantines varies by growing region, commodity and level of infestation.

Light brown apple moths damaged these organic berries at a Santa Cruz County farm.

State and federal quarantine regulations prohibit movement of nursery stock, cut flowers and host fruits and vegetables within or from a quarantined area, unless inspected and certified as pest free by an agricultural official.

The light brown apple moth is native to Australia and is found in New Zealand, the United Kingdom and Hawaii. It was found in California for the first time in the spring of 2007.

In the Watsonville area, about 20 percent of ripening blackberries in a 100-acre organic planting were damaged by the moth infestation this spring. Larvae were found on berries, as well as webbing.

"This the first time we've seen so many light brown apple moths in the field," said Mark Bolda, University of California Cooperative Extension berry crop advisor in Santa Cruz County. "The damage is without precedent. As the moth is becoming more numerous in the area, we're starting to see this sort of thing."

Bolda said blackberry farmers have faced damage from leaf-roller-type insects, such as the light brown apple moth, for a long time. But as an invasive species, unlike native species, it has no predators to control its population growth and curb crop and environmental damage.

"In the grower community here, we'll have to be more proactive in fighting this pest," Bolda said. "In the past we've held off on treatments, but now we may need to start treatment earlier," because the presence of a single larvae can trigger a quarantine.

"This pest has got to be eradicated from our fields," he said. "We have positive laboratory confirmation that light brown apple moth is doing the damage in our fields."

Since 2007, about 36,000 light brown apple moths have been trapped in Santa Cruz County, making it one of the state's most highly infested food production areas. Throughout the state's quarantine areas, however, nearly 100 nurseries, cut flower or greenery farms have been found to have light brown apple moth larvae and pupae. To date, direct crop damage has been restricted to the organic berries.

Claudia Reid, policy and program director for Santa Cruz-based California Certified Organic Farmers, said her organization is "seriously concerned" about the pest's effects on organic and non-organic farmers alike.

"Insects that have the potential to threaten entire crops also threaten farmers' livelihoods," Reid said. "Organic farmers, like all farmers, are committed to preventing the spread of this pest, and they have organic pest control methods at their disposal that need to be used in response."

In particular, she said, if the infestations result in a quarantine, the ability for farmers to move produce around the state or out of state is greatly affected.

"For example, such quarantines mean that farmers wanting to sell vegetables at neighboring county farmers markets would be required to have a USDA inspector on site before harvesting many of their crops, which takes time and costs money."

A new quarantine of approximately 38 square miles has just been established in Yolo County, near Davis, following detection of a second light brown apple moth in the area.

In Sonoma County, where more than 80,000 acres of premium winegrapes are produced, about 20,000 acres are under federal quarantine. The county's apple orchards are also at risk of infestation and pest damage, which officials suspect is spreading from untreated urban areas.

Agricultural officials and farmers in Sonoma and Napa counties are taking steps now to ensure their crops will be in compliance with quarantine restrictions, to avoid problems with shipping commodities at harvest.

Sonoma County quarantines now affect more than 800 farmers of various crops, officials said. The $416 million winegrape crop, however, is by far the county's most valuable agricultural commodity.

"We're fairly satisfied with the government response to this pest threat," said Nick Frey, president of the Sonoma County Wine Grape Commission. "It will be a cumbersome process to harvest the 20,000 acres under quarantine today. And, I think there may be some expansion with new pest finds in the coming months."

He said the commission recommends that winegrape growers who are not in the quarantine areas go ahead and complete the compliance process for shipment out of quarantine areas, because the number of acres affected has been rapidly expanding.

"They found 45 moths in the county last month and I expect they'll find more than that this month," Frey said. "If the quarantines are expanded at harvest, growers will already have filled out the necessary paperwork for inspections and shipment."

Officials said populations of the light brown apple moth, identified in California about two years ago, now appear to be reaching sufficient size and density to inflict crop damage.

"The reality is that the levels of infestation we're now witnessing call into question the assertion that the light brown apple moth had been in California for an extended period of time," said Barry Bedwell, president of the California Grape and Tree Fruit League.

"The evidence of damage, and the risk of the pest spreading, underscore the need for a credible control and eradication program," Bedwell said.

State and federal agricultural officials are currently developing sterile insect technology to combat the infestation.

"We support the male sterile moth program as a tool to disrupt breeding cycles," Bedwell said. "We are concerned about the costs of the programs and we urge elected officials at the state and federal levels to consider the risk of not funding control and eradication measures for this pest."

The light brown apple moth attacks a broad range of host plants, with more than 2,000 plant species—including 250-plus crops—known to be susceptible.

It threatens California's environment by destroying, stunting or deforming young seedlings and damaging new growth in the forest canopy. The moth also feeds on host plants and damages or spoils the appearance of ornamental plants, citrus, grapes and deciduous tree fruit crops.

For more information on the light brown apple moth, visit www.cdfa.ca.gov/lbam.

(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at kcampbell@cfbf.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item. Top