This story has been modified since its original posting.

Fallbrook farmers could be facing another winged threat to their crops.

County and state agriculture officials recently trapped the county's first light-brown apple moth in a lemon tree in eastern Bonsall, San Diego County Agriculture Commissioner Bob Atkins said Monday.

The March 2 discovery was in the 3200 block of Caminito Quieto.

Atkins said county workers are hanging more traps in the area, adding that the discovery of a second moth would trigger a quarantine that would last until at least until August.

Fallbrook and Escondido farmers are already under quarantine for the Mediterranean fruit fly, so a moth quarantine would force some farmers to fight off two pests with different treatment methods.

The light-brown apple moth is native to Australia. It lives on leaves and threatens more than 250 fruits and vegetables and more than 1,000 plants, including redwoods, oaks and cypress trees.

Officials said a statewide moth infestation could cost California up to $133 million annually in lost crops and pest control costs ---- or enough money to provide food stamps for one year to nearly 40,000 households.

Agriculture officials trapped the state's first light-brown apple moth March 22, 2007, in Alameda County.

The moth has since been captured in 11 additional counties, including San Francisco, Santa Barbara and Santa Cruz.

The Santa Cruz County Farm Bureau estimated that wholesale and retail nurseries lost about $2.8 million in sales and investments in efforts to eradicate the moth from April through December 2007.

A quarantine triggered by the discovery of a second moth in Fallbrook would fan out 11/2 miles in every direction from the site of each captured moth, Atkins said.

He said fruits and vegetables could be shipped out of the quarantine areas only after they have been brushed free of leaves and stems.

Plant nurseries would be most affected because they would have to treat plants with pesticides before they could be shipped, Atkins said.

Treating crops to fight the moth has caused problems in the past.

In fall 2007, hundreds of people in the area surrounding Monterey and Santa Cruz complained of feeling sick after planes sprayed the area for the first time.

State environmental health experts said in 2008 they couldn't tie the pesticide spraying to the illnesses.

A judge halted spraying over Santa Cruz County pending a full environmental review of the treatment program.

Since then, officials have been dropping sterile moths into the area as a way to keep the pest from reproducing.

Officials adopted a similar approach in fighting the local medfly infestation by flooding the quarantine areas with sterile male flies.

The fruit fly can live in more than 260 kinds of fruits and vegetables.

Farmers and even home gardeners are not allowed to move fruits or vegetables during the quarantine until the food has been treated and certified as safe to move and sell.

Officials said the quarantines are designed to prevent a permanent Medfly infestation that could cost the state $1.8 billion annually in lost crops, lost jobs and trade restrictions.

Fallbrook's 79-square-mile quarantine began in November and is expected to last until late July.

The 148-square-mile quarantine in Escondido began in September and was expanded in December when more flies were found. It is expected to last until August.

Contact staff writer Morgan Cook at 760-740-3516.

CORRECTION: Length of possible quarantine incorrect

The original version of this story should have said a possible quarantine would last until at least August. The article said incorrectly that it would last at least 18 months. It has been corrected.

We apologize.