The California Department of Food and Agriculture (CDFA) is preparing to treat the Ukiah-Hopland area in Mendocino County as part of the ongoing effort to eradicate the European grapevine moth (EGVM) from backyard grapevines.

CDFA’s first choice for treatment is fruit removal from backyard grapevines within 400 meters of where a EGVM was found. The second choice is ground treatment with the organic compound Bt, or bacillus thuringiensis, a naturally-occurring extract from bacteria.

Either option will help eradicate EGVM on the properties and greatly reduce the risk of spread to commercial vineyards, CDFA says.

Approximately 1,000 residential properties are within the designated treatment areas. Some contain grapevines which are the only EGVM host plant to be treated.

Fruit removal activities are scheduled to begin in the Ukiah area next week.

An informational open house to discuss the program is scheduled for Tuesday, Aug. 31, 5:30-7:30 p.m. at the Alex Rorabaugh Center, 1640 S. State St. Ukiah, Calif.

The European grapevine moth has been detected in eight California counties: Fresno, Merced, Monterey, Napa, San Joaquin, Sonoma, Solano, and Mendocino.

The pest is known to occur in southern Asia, Japan, Europe, North Africa, Anatolia, the Caucasus, and in South America. It primarily damages grapes, but has also been known to feed on other crops and plants.

The EGVM larvae, not the adult moths, are responsible for the damage to grapes. Larvae that emerge early in the spring feed on grape bud clusters or flowers and spin webbing around them before pupating inside the web or under a rolled leaf.

If heavy flower damage occurs during this first generation, the affected flowers will fail to develop and yield will be reduced. Second-generation larvae chew into the grapes to feed before pupating in the clusters or in leaves.

Larvae of the third generation - the most damaging - feed on multiple ripening grapes which are further exposed to further damage from fungal development and rot. The larvae overwinter as pupae in protected areas such as under bark, and emerge as adults the following spring.