The California Department of Food and Agriculture will begin a counter offensive on the European grapevine moth (EGVM) with a control effort focusing on backyard vineyards in the area where EGVM were first detected in Fresno County.
State and county officials will either remove young fruit from vines or treat with a benign insecticide to control second-generation EGVM at 16 private residences in the Del Rey area. These residences have been described as small one- to three- acre parcels for families with horses and other small animals and gardens.
According to a spokesman at the Fresno County Agricultural Commissioner’s office there are only about 60 individual vines targeted at these residential, rural properties. EGVM’s primary host is grapes.
These locations are within about a half mile of where EGVM were caught in pheromone traps earlier this spring.
The region is called the “core area” within the 96 mile quarantine area established after several EGVM were trapped.
These targeted properties do not involve commercial vineyards.
CDFA’s first choice for treatment is fruit removal from grapevines. If property owners would prefer otherwise, the second choice would be ground treatment with the organic compound Bt, or bacillus thuringiensis.
Either option will control EGVM on the properties and greatly reduce the risk of spread to commercial vineyards, according to members of the eradication team.
Fruit removal activities are scheduled to begin in the Del Rey area this week. If property owners choose Bt instead, treatment would occur next week. An informational open house to discuss the program is scheduled for today (June 25), from 5-7 p.m., at the Fresno County Department of Agriculture Building, West Wing Conference Room, 1730 S. Maple Ave. Fresno.
The European grapevine moth has been detected in seven California counties: Fresno, Merced, Monterey, Napa, 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 and expose them to further damage from fungal development and rot. These larvae overwinter as pupae in protected areas such as under bark, and emerge as adults the following spring.