A new insect threat has appeared on the radar for California vintners. Infestations of the light brown apple moth, a pest native to New Zealand and Australia, have been confirmed in eight counties by the California Department of Food and Agriculture (CDFA), which on April 20 established a quarantine encompassing 182 (noncontiguous) square miles.
The insects feed on more than 200 plants found in California, including peaches, citrus, tomatoes, avocadoes and grapevines. Infestations have been discovered in Alameda, Contra Costa, Marin, Monterey, San Mateo, Santa Clara, San Francisco and Santa Cruz counties. Nearly all of the finds have been in urban areas, suggesting to CDFA officials that it has spread on nursery stock, one of its preferred hosts.
Infestations have yet to be found in vineyards, but the moth can do substantial damage to vine leaves, flowers and grapes. In Australia, the moth can be significant problem. "It varies from year to year. If it's too hot you see less, and in milder years you see more," said Kym Ludvigsen, viticulturist for Taltarni Vineyards in the Victoria region. "If it gets into the bunch and creates avenues for botrytis it can cause 15, 20 or 30 percent crop loss depending on the season."
CDFA officials are still in the early stages of their investigations. "We're still setting and inspecting traps. One advantage with this pest is that there's a highly effective pheromone trap that will allow us to determine the extent of the infestation," said Jay Van Rein, spokesman for the CDFA.
In Australia, the moths have three or four generations per year. If the insects are caught early in the larval stage they are fairly easy to kill with an organic spray, said Ludvigsen. "But once the caterpillars get larger, especially if they get inside the bunches [where sprays don't reach], it's hard to control."
Agriculture officials are placing about 300 traps in Napa that will be inspected every two weeks, said Greg Clark, assistant agriculture commissioner of Napa County. "So far we've been fortunate [not to get it in Napa], but I expect that as the investigation progresses it will be found in other counties," he said.
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