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To spray or not? 

SLO County prepares for battle but expects to avoid controversial pheromone spraying

click to enlarge CERTIFIED :  Hope Merkle holds the certificate proclaiming that the Los Osos Valley nursery she manages is cleared of Light Brown Apple Moth. Five of the invasive moths were found in Los Osos, prompting the state to issue a quarantine. - PHOTO BY STEVE E. MILLER
  • CERTIFIED : Hope Merkle holds the certificate proclaiming that the Los Osos Valley nursery she manages is cleared of Light Brown Apple Moth. Five of the invasive moths were found in Los Osos, prompting the state to issue a quarantine.
It’s just a little brown moth, indistinguishable to the untrained eye from any other moth, but the invasive Light Brown Apple Moth has launched state, local, and federal officials into a frenzied effort to stop its spread.


California is the only state in the country known to harbor the moth and government officials have gone to lengths to keep the problem from spreading. Last year the California Department of Food and Agriculture, which is acting as a lead agency, spent more than $18 million ($16 million of that was provided by the USDA) to keep the pest at bay.


Some of the efforts involved have proven controversial. Aerial spraying of the moth’s pheromone over urban populations in Santa Cruz and Monterey counties, which was intended to disrupt the moths’ breeding, led to a lawsuit. Earlier this month, the state released an Environmental Impact Report as a result of that case, with several other options for extermination. Any decisions regarding aerial spraying, SLO County Agricultural Commissioner Bob Lilley said, will be made by the state, but he said aerial spraying is unlikely to happen here.


The area will, though, be affected in other ways.


The entire town of Los Osos was “quarantined” by the state Aug. 19, after five of the moths were found at a home there. As far as the feds are concerned, the whole county is quarantined, along with more than a dozen others in the state. Combined, it means extra scrutiny for agricultural and nursery products headed out of state from 55 vegetable producers and 36 nurseries in the county.


The apple moth isn’t much different than other native species of moth, except that it’s not native. It’s indigenous to Australia, where it is considered a pest. And in New Zealand it’s considered a plague. Actually, it’s not the moth that worries agriculturalists so much as the caterpillars, which have voracious appetites and indiscriminate tastes. The caterpillars are known to eat the leaves of more than 2,000 different wild and agricultural plants, including grapes.


David Headrick is a professor at Cal Poly, where he teaches several classes on pest management. He’s also been on the governor’s Environmental Advisory Task Force for Light Brown Apple Moth since 2008.


“The big question,” Headrick wrote in an e-mail, “is how far and wide will it spread and of all the plants it likes to eat, which ones will it really be a significant pest on. We know from New Zealand’s experience that pome fruits and grapes will likely be affected.”


Right now in the U.S. the pest is confined to coastal California, concentrated in the Bay Area, where it was first discovered in 2007, and in Santa Cruz County. A single adult moth was found in Cambria in 2007, but none were found in SLO County during 2008. Since then, more than 26,000 traps, baited with the female moth’s sex pheromone, have been placed around the state. SLO County traps have caught a total of six moths.


The Los Osos quarantine was issued by state agriculture officials, after the moth was positively identified July 14 and again July 27. The moths were all found at the same residence, leading officials to think they may have come on a plant from an out-of-town nursery. Much of the focus to control the moth is on commercial operations, such as nurseries and farms, which now have to undergo frequent inspections and receive moth–free certification.


So far, the pest has not been found on any farms or nurseries in Los Osos. Hope Merkle, who manages Los Osos Valley Nursery, said the increased attention on nurseries is welcome. She said inspectors have been coming by the nursery for the past couple of weeks. They seized a moth and two caterpillars from her nursery, which turned out not to be Light Brown Apple Moth.


“It used to be that they inspected for snails and weeds,” Merkle said. “I think they’ve lightened up over the years. Now they just look for specific bugs.”


Lilley said he intends to ask the state for $60,000 to combat the pest. That’s $10,000 for each moth that has been found locally but it’s an expense Headrick said could pay off in the long term. For one thing, agriculture officials aren’t just looking to control the moth, they’re looking to eradicate it. As soon as the state’s Environmental Impact Report is approved, eradication can start. So ag officials are coming on strong, and hoping to keep the pest in isolated areas.


And it isn’t only Californians who are concerned about the moth spreading.


“We need to look at where else in the world the pest occurs,” Headrick said, “Because that seriously affects our ability to sell and move our agricultural products. And that is where [the apple moth] fits in.  We’re the only place in North America to have it and one of a very limited number of countries that has it. That puts a significant stranglehold on our domestic and foreign markets.”


Kylie Mendonca is light brown and ingests apples in moth-eaten clothes. She can no longer be reached at



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