Since that sighting of the light brown apple moth - thought to be the first in the continental United States - trappers have found about 75 more throughout the San Francisco Bay area, evidence that the voracious pest is breeding.
Now, state and federal officials are considering slapping a quarantine on the more than 250 plants the invasive moth eats - everything from grapes to oranges to redwood trees - to avoid an estimated $133 million in annual losses to California agriculture.
On Monday, the state Department of Food and Agriculture ordered nurseries in eight cities where the moth has been spotted to inspect their plants before shipment, hoping to keep the apple moth away from the fertile San Joaquin Valley.
"This pest likes oak trees and it likes ornamental plants in people's yards," department spokesman Steve Lyle said. "But it's a major threat to the production of agriculture should it become established in the Central Valley."
Trappers have found the light brown, yellowish insects in an area measuring nearly 120 square miles.
It has not turned up at farms or nurseries. But peach, apricot, and nectarine farmers and grape growers are already worried about what a moth infestation could do to their crops.
"We're very concerned because there are so many hosts to this thing," said Tony Fazio, who grows and ships table grapes in Fresno County. "You can't underestimate the damage that's possible with these pests when you don't understand them."
As caterpillars, the dime-sized moths eat insatiably, chomping through fruit, leaves and bark. They can kill or deform seedlings, mar the appearance of ornamental plants and spoil stone fruit crops. In Australia, the species causes annual crop losses of about $17.2 million.
With a wingspan of just 16 to 25 millimeters (less than an inch), the moths usually spread not through flight, but by laying their eggs on the leaves of trees or nursery plants, or traveling hidden inside fruit or greenwaste.
Agricultural authorities in Australia, New Zealand, New Caledonia, Hawaii and the British Isles have used a variety of techniques - including mating disruption, parasitoids and various insecticides - to keep new generations from hatching.
The U.S. Department of Agriculture has assembled an international team of experts to discuss how to deter the pest in the California landscape.
A spokesman for the team did not return calls Tuesday seeking comment on their findings.Once officials identify the pests' reach, they will likely quarantine all host plants until shippers can prove they are moth-free, Lyle said. In recent years, similar strategies have helped kill off infestations of peach fruit flies and Mediterranean flies, he said.Farm associations said a quarantine would address the problem, but suggested the moth could have been kept out of the country through better pest control at airports, seaports and other border crossings.According to a recent Government Accountability Office report, the number of agricultural inspections at San Francisco ports of entry has fallen by 21.4 percent in the last four years, since the Animal and Plant Inspection Service moved under the jurisdiction of the Department of Homeland Security from the USDA."We have to recognize we have a really serious problem," said Barry Bedwell, president of the California Grape and Tree Fruit League. "We're worried not only about what this little moth can do to the fruit itself, but also what it could mean in terms of agricultural trade."