VASCM: Current efforts to eradicate EGVM in So. Santa Clara County

[Mary Lindsay, Muns Vineyard]

For your information:

This is an update on current efforts to eradicate the EGVM in South 
Santa Clara County
from the Gilroy Dispatch, April 11, 2011:


*County plans to eradicate grapevine moths, 90 properties affected*
By Lindsay Weaver <mailto:lweaver at svnewspapers.com>

The European grapevine moth infestation in September 2010 that led to 
the quarantine of 93-square miles in South County is getting more 
attention from the Santa Clara County Department of Agriculture this 
week as an eradication plan will begin in Gilroy shortly.

Treatment will start near the intersection of Day Road and Watsonville 
Road. Three moths were found last year - enough to cause a scare in the 
affected neighborhoods.

The eradication effort will focus on "intensive trapping" in vineyards 
and backyard grapevines at about 90 properties within the treatment 
area, according to a county press release. Flower and fruit removal from 
grapevines is scheduled to begin as soon as next week.

The moths found in September near Watsonville Road, north of Day Road 
are third generation adult moths, which could become the most damaging 
version - as worms - if they become active in the springtime. Now and 
into the winter they will go dormant, but in the spring they will feed 
on ripening grapes and expose them to further damage through fungal 
infections. The moths can cause the grapes to brown and rot and can ruin 
an entire crop if they reproduce and spread.

The European grapevine moth larvae, not the adult moths, are responsible 
for the damage to grapes. Larvae (worms) emerge early in the spring and 
feed on grape bud clusters or flowers, according to the press release. 
The larvae then 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 generation, feed on multiple ripening grapes and 
expose them to further damage from fungal development and rot. These 
larvae through winter as pupae in protected areas such as under bark, 
and emerge as adults the following spring.

The California Department of Food and Agriculture's first choice for 
treatment is flower and fruit removal from backyard grapevines within 
500 meters of where European grapevine moth was found. If property 
owners prefer otherwise, the second choice is ground treatment with the 
organic compound "Bt," or bacillus thuringiensis, a naturally-occurring 
extract from bacteria.

The treatment options will be provided at no cost to the homeowners. 
Both options will help to eradicate European grapevine moth and greatly 
reduce the risk of spread to commercial vineyards, according to the 
press release.

To date, the moth has been detected in 10 California counties: Fresno, 
Merced, Monterey, Napa, San Joaquin, Santa Clara, Santa Cruz, Sonoma, 
Solano and Mendocino. The pest is known to occur in southern Asia, 
Japan, Europe, and North and South America. It primarily damages grapes, 
but is also known to feed on other crops and plants.

*Earlier this month, three additional European grapevine moths were 
trapped within the quarantined area.*