Add Santa Clara County to the eight other California counties where infestation levels of European grapevine moths (EGVM) have been trapped and quarantines established.

Three EGVM moths were snagged in pheromone traps in mid-September in south Santa Clara County which prompted state and federal officials to establish a 93-square mile quarantine area bounded by Gilroy, Morgan Hill and the eastern edge of Santa Cruz County, according to Kevin O’Day, Santa Clara County acting agricultural commissioner.

This brings the total for statewide quarantine areas to more than 2,000 square miles in Mendocino, Sonoma, Lake, Napa, Solano, Merced, Fresno, San Joaquin and now Santa Clara counties.

Although large, this total area represents a small part of the state’s total 40-county grape growing area.

However, the latest find of third-generation moths in Santa Clara must heighten concern statewide for the $4 billion grape growing industry.

EVGM was first detected in Napa County in September of 2009. It was the first time EGVM had been detected in the U.S.

EGVM feeds only on grape bunches. It is a pest of major economic importance in Europe, North Africa, the Middle East, southern Russia, Japan, and recently Chile.

Second and third generations cause the most damage by direct feeding on mature grape berries and indirectly by predisposing the crop to bunch rot.

Damage is greatest in grape cultivars with compact clusters or sensitive to rot.

The initial infestation in Napa County can only be characterized as significant. At least one grape grower lost his entire crop to the pest that year. This prompted the state to begin an aggressive trapping program statewide to see if it had spread. The state deployed 47,000 traps in all grape growing areas of the state.

With the multiple finds in widely separated areas of the state, government officials have urged growers to aggressively treat for the pest. They have ordered homeowners in quarantine areas to destroy backyard grape crops.

In the spring of 2010, trap counts in the Napa area numbered in the thousands, indicating a well-entrenched, if not resident EGVM population. Growers have been aggressively spraying to prevent an established population and have had success.