Grapevine Pests

NVG provides its members with regular reports on vineyard pests and diseases, including resources on best practices for choosing plant material and timely updates on viruses and pest management. NVG members hold positions on the Napa Winegrape Pest and Disease Control District Board, the PD/GWSS Board, as well on CDFA's Regulations Working Group, to promote and manage funding for pest and disease research, education, and prevention efforts supporting Napa County vineyards.

General Resources

Napa County Agricultural Commissioner
ph. 707-253-4357
Dr. Monica L. Cooper, UC Farm Advisor
ph. 707-253-4221 
CDFA Pest Hotline
1-800-491-1899
University of California Agriculture and Natural Resources - UC IPM Pest Management Guidelines

Erineum Mite

Recently identified as a vector of GPGV, erineum mites are generally considered aesthetic rather than economically damaging pests. Occasionally, large populations damage young vines. A reduction in sulfur use for powdery mildew has potentially exacerbated erineum mite populations. In-season or post-harvest sulfur treatments can reduce the incidence of galling in the following season.
Resources:
UC IPM Guidelines
NVG Viticultural Best Practices Video - Mites (English)
NVG Viticultural Best Practices Video - Mites (Spanish)

European Grapevine Moth (EGVM)

As of August 2016, EGVM was declared eradicated from California. Statewide monitoring continues for incipient populations. Growers should remain vigilant, inspecting fruit for larval stages (caterpillars). Post-veraison, inspect the fruit for characteristic holes and larvae feeding inside the softening fruit.
The recent eradication of EGVM required mandating federal and state permits, inspections, quarantine zones, and strict restrictions on movement of all grapevine plant material—at the cost of $115 million in public and private funds. Dozens of vineyard pests currently pose a similar threat, where moving material from a vineyard to other locations could hasten their spread. As such, grapevine woody debris is best disposed of on-site and through disease eliminative processes such as burning.
Resources:
UC IPM Exotic and Invasive Pest Guidelines: damage, identification, monitoring and management
CDFA Resources
CDFA Pest Profile
USDA Pest and Disease Program
Napa County Information on European Grapevine Moth

Grapevine Fanleaf Virus (GFLV)

GFLV is present in Napa County and can become a greater issue if not adequately mitigated. A primary mitigation strategy includes planting O39-16 rootstock
Resources:
CDFA Grapevine Fanleaf Disease

Mealybugs

Grape (GMB) and vine (VMB) mealybugs are the most common species in Napa vineyards. GMB is a native insect and is generally under biological control, except when broad-spectrum insecticides or Argentine ants disrupt the biological control agents. VMB is an invasive species that has been expanding its range in Napa since it was first reported in 2002. VMB populations can be very damaging and challenging to control. A combination of mating disruption, biological control, ant control, and insecticides may be required to manage VMB populations. In addition to the direct feeding damage, both VMB and GMB are vectors of GLRaV-3. Inspect nursery stock (green-growing) for presence of VMB before planting.
Resources:
UC IPM Guidelines
Napa County Information on Vine Mealybugs
CDFA Mealybug Pests of Winegrapes
Vineyard Mealybugs | UCCE Vit Napa
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Sharpshooters

Blue-green, green, willow, and red-headed sharpshooters are found in northern California. The glassy-winged sharpshooter (GWSS) is present in southern California; multiple programs are in place to minimize risk of movement of GWSS into northern California. These programs encourage the local purchase of ornamental plant material; county officials in the Agricultural Commissioner’s office should be notified to inspect all plant material that comes onto a property. All sharpshooters are vectors of the Pierce’s Disease pathogen, Xylella fastidiosa. Yellow sticky traps or sweep nets can be used to sample for these insects.
Resources:
UC IPM Guidelines
Napa County Information on Glassy-winged Sharpshooters
California PD/GWSS Board

Spotted Laternfly (SLF)

SLF is a relatively new pest that is spreading in the Eastern United States.   First introduced into Pennsylvania in 2014, it has spread to Virginia, New York, New Jersey and Delaware. SLF has become a serious pest of grapes in Pennsylvania as well as in Korea.   SLF is a planthopper that produces large amounts of honeydew that leads  to black sooty mold that damages fruit.  There is the potential for SLF to spread to California via egg masses, which are laid on hard surfaces such outdoor furniture, tools, barbeques, etc.  
Resources:
SpottedLaternfly.com
Pest News: Spotted Laternfly (February 2018)

Three-Cornered Alfalfa Hopper (TCAH)

TCAH has been shown to transmit Grapevine Red Blotch Virus in both greenhouse and field trials. Preferred host plants for TCAH include legumes closely related to alfalfa. At this time, grapevines have not been shown to be a preferred host of TCAH. Ongoing studies are investigating whether control of the preferred host plants (by cultivation or mowing) could reduce populations of TCAH.
Resources:
UC IPM Guidelines

Variegated Leafhopper (VLH)

Because VLH lays its eggs deep within the leaf tissue, they are less susceptible to parasitism than western grape leafhopper. Therefore, larger populations can develop in the absence of treatment; larger populations can defoliate vines prematurely, affecting vine health and berry ripening. It is important to be able to distinguish between the various leafhoppers to ensure proper treatment selection and timing.
Resources:
UC IPM Guidelines
NVG Viticultural Best Practices Video - Leafhoppers (English)
NVG Viticultural Best Practices Video - Leafhoppers (Spanish)

Virginia Creeper Leafhopper (VCLH)

First reported in Napa County from Pope Valley, VCLH has continued to expand its range, with populations now occurring east of St Helena. Because its life cycle is different than the more common western grape leafhopper (WGLH), spray timing to control VCLH is shifted compared to WGLH. If treatments are made at the proper timing, VCLH is well controlled by one application of a neonicotinoid or insect growth regulator. Organic growers rely on multiple oil or pyrethrin applications.
Resources:
UC IPM Guidelines
NVG Viticultural Best Practice Video - Leafhoppers (English)
NVG Viticultural Best Practice Video - Leafhoppers (Spanish)

Western Grapeleaf Skeletonizer (WGLS)

The Western Grapeleaf Skeletonizer (WGLS) is a significant and destructive winegrape pest not known to be established in Napa County. All larval life stages are voracious feeders that cause extensive leaf damage, including partial or complete defoliation of grapevines, especially on young vines. Excessive and uncontrolled feeding can damage fruit and lead to secondary fungal damage and rot of winegrape clusters. WGLS is well-controlled by an entomopathogen in regions where it is established, with infection rates regularly reaching or exceeding 80%.
Resources:
Photos and UCCE's WGLS Monitoring Guide