Jul 2, 2008

County becomes moth quarantine area

By Julia Scott / Bay Area News Group

Proliferation of the light brown apple moth across San Mateo County in recent months has prompted state officials to put most of the Bayside into a continuous moth quarantine area, and the county is asking residents to take measures to stop them from spreading even further.

This week's announcement places San Mateo County cities from Millbrae to Woodside within the quarantine zone and reflects the fact that the number of male light brown apple moths trapped inside the county now stands at 286 - far fewer than in San Francisco, but still a 79 percent increase over the total detected this past February.

County Department of Agriculture Commissioner Gail Raabe attributed the increase to warm spring weather, which speeds up the moth's life cycle, allowing it to reproduce more quickly. The county has no active moth treatment program other than in Half Moon Bay and Pescadero, where pheromone-coated twist-ties were wrapped around tree branches last February to disrupt the moth's mating patterns.

Although the moth feeds on hundreds of different plant and tree varieties, it seems to prefer the flowers, plants and vegetables grown in greenhouses and commercial nurseries, said Raabe. That would explain why Daly City and other North County cities continue to be so widely affected by the insect. Officials suspect nurseries there imported plants containing light brown apple moth eggs from Santa Cruz. Proximity to San Francisco is also a factor.

Quarantines have been in place in those areas for months, which means the county periodically sends biologists to 56 cut-flower and vegetable growers and 25 retail nurseries to inspect their products before they're delivered. Raabe believes that in spite of those efforts, several moths now also feed on fruits and flowers in residents' backyards in places like San Mateo, Foster City and Woodside.

"We've detected the moth in what were previously the blank areas in the map. It no longer made sense from a regulatory point of view to have these distinct quarantines," Raabe explained.

The original quarantine zones have been in place since last April, and the county is using nearly 3,000 traps to eliminate the moths.

In an effort to contain the spread, county agriculture officials are asking residents in the quarantine zone to be very careful not to give away any flowers, plants or fruit from their backyards because they might contain unseen moth eggs. Yard waste and compost should also be kept on-site unless it is being disposed of by a licensed recycling or trash hauler.

"Not every neighborhood has the moth. You don't know you're not bringing cut flowers from your yard into an area that doesn't have them yet," cautioned Raabe.