The 4,000 pheromone traps (one per 20 acres) in Napa County are telling the success story.

 “At the end of last season there were vineyards with really bad EGVM infestations," says Martin Mochizuki, Napa County’s EGVM grower advisor. “We were seeing almost one larva per berry.”

This year, about 99,000 first-generation moths were caught in 4,000 pheromone traps deployed countywide. “During sunset, at the peak of the first flight, you could see the moths swarming like mosquitoes,” says Napa County EGVM grower adviser Martin Mochizuki.

Following an aggressive first-generation treatment effort by growers in the infested area, only 1,300 moths were trapped in the second generation. By the third generation, the trap count had dwindled to only about 100. No grape damage was reported from the second EGVM generation. So far, he has heard of only one vineyard being damaged by third-generation larvae.

Napa growers have spent about $150 per acre for conventional insecticides to control EGVM and $250 per acre for organic products.

Grower costs like that statewide to control EGVM would have a significant impact on many economically struggling wine grape growers.

The quarantines triggered by multiple moth finds are particularly insidious where fresh fruit crops other than grapes are grown since the quarantines involve hosts of crops. It doesn’t cause major damage in non-grape crops, but it can survive on olives, plums, apricots, cherries and many other crops and ornamentals.

When a quarantine is triggered, growers and all processor within the quarantine boundaries must sign "compliance agreements" to sanitize equipment moving in an out of the areas as well as agree to other measures to prevent the spread of EGVM. These quarantines remain in effect for at least year, even if no more EGVM are detected in the area.

Single moths also have been trapped in Santa Cruz and Monterey counties. It takes at least two EGVM moth/larvae finds to trigger a quarantine. Also, at least one county, Yolo, is monitoring the movement of grapes into that county from know EGVM quarantine areas.

When EGVM moths were trapped in early spring outside of the North Coast, regulators were adamant about the fact that these catches did not mean EGVM populations were established outside of the North Coast.

Most want to be optimistic that EGVM can be eradicated. However, with each find comes growing concern that the state’s grape industry is in a real fight to keep EGVM from becoming established statewide.