Pests and Diseases
New Moth Threatens Napa Valley Wine Industry and Beyond - Eurpoean Grapevine Moth
A new, destructive grape pest known as the European Grapevine Moth (EGVM) has invaded Napa County and caused significant damage to crops in 2009, including the total loss of an 11-acre Chardonnay vineyard in the Oakville area. Trapping for EGVM has shown that the moth has spread throughout Napa County and has been found in Fresno, Mendocino, Merced, Monterey, San Joaquin, Solano and Sonoma counties.
According to Napa County Agricultural Commissioner Dave Whitmer, "This is an invasive moth—we are doing all we can, working with our state and federal partners, to implement a plan to combat this pest in Napa County."
As part of the overall strategy, Whitmer is leading the efforts to ensure Napa Valley vineyard operators are treating for EGVM, and has hired additional staff to work with growers in treatment methods. Treatment includes applying pest control methods regularly on vineyards in infested regions and using pheromone-mating-disruption twist ties to confuse male moths on the location of female moths.
Treatment seems to be working. The Chardonnay vineyard referenced above has undergone treatments and mating disruptions, resulting in what appears to be complete control of the infestation in that vineyard. Government regulations are in affect for all vineyard and winery owners that are harvesting, moving or processing winegrapes to combat the spread of the moth to areas outside the infestation. Growers and vintners must sign agreements with the Ag Commissioners office prior to harvesting, moving or processing winegrapes in Napa County.
For residents of Napa County not involved in the wine business the Napa County Ag Commissioners office believes that if you have grapevines, you may have EGVM. To help combat the moth, residents can:
1. STRIP YOUR VINES: remove all grape flowers or clusters from your vines with pruning shears; and
2. KICK 'EM TO THE CURB: place the grapes in your brown yard waste container and keep the lid closed.
OR: treat grapes with an approved organic insecticide.
Home-use products that contain Bacillus thuringiensis (Bt) or Spinosad are suitable products to use to control European Grapevine Moth larvae in winegrapes. These products are available at retail nurseries and garden supply centers. Please follow the label directions regarding the frequency of applications and any safety precautions.
To learn more about the European Grapevine Moth or to determine if you live near an area with a high infestation please visit the Napa County Ag Commissioners website .
Glassy-Winged Sharpshooter (GWSS)
The Glassy-Winged Sharpshooter (GWSS) is a non-native pest (meaning it was not originally found in California). The GWSS spreads a variety of diseases to crops and ornamental plants including Pierce's Disease - a disease about which you may have heard and which infects grapevines. Pierce's Disease blocks the circulatory systems of a plant, choking off its food and water supply. The GWSS is so dreaded because it is voracious and highly mobile and can spread Pierce's Disease from plant to plant quickly and easily.
A typical GWSS will drink approximately 13 milliliters of water per day (200-300 times its own body weight) - which it sucks from the unfortunate host plant. That's the same thing as a human drinking 4,300 gallons of water per day!
What you can do to help:
- Go to www.bugspot.org to learn more about the GWSS. If you think you have spotted a GWSS, call 1-866-BUG-SPOTâ€¨.
- Look for the Certificate of Compliance at your local nursery or landscaper's office. This means that they have been inspected by the Napa County Agricultural Commissioner. Be vigilant in buying locally.
- Check your outdoor plants regularly. Be on alert for the GWSS when walking in local parks and recreation areas.
While the State of California enacted emergency regulations to stop the spread of the GWSS, it is the consensus of the Napa Valley wine industry that these regulations do not go far enough. As a result, Napa County has enacted the toughest regulations in the state to stop the harmful pest from ever entering our county. The NVV, along with Senator Wes Chesbro, also sponsored legislation- that was signed by Governor Davis- to allow a mandatory assessment on vineyard land in Napa County creating a permanent source of funding for Napa County's work plan.
One significant reason for these tougher regulations is so that we will never have to be put in the position of using pesticides to eradicate the GWSS. The Napa Valley plan was developed by the Glassy-Winged Sharpshooter Action Team -- the Napa County Agricultural Commissioner, the wine industry, the nursery industry, and environmental groups -- and approved by the State Department of Food and Agriculture.
For further information about the Glassy-Winged Sharpshooter or the Action Plan - visit the Web site of the Napa County Agricultural Commissioner at www.co.napa.ca.us/internet/content/departments/agcom/agcom.asp