Since it was accidentally imported from Asia to North America in the mid-1990’s, BMSB has become a serious nuisance pest in urban areas. In the mid-Atlantic states, it is also a pest of vegetable, fruit and ornamental crops. Monitoring efforts for BMSB in agricultural regions of CA are ongoing. So far, most populations in CA are associated with urban areas; no reproducing populations have yet been found in CA vineyards. Several BMSB have been trapped in Napa County.
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.
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.
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.
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.
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.
Under laboratory conditions, TCAH is a vector of grapevine red blotch virus; field studies are ongoing. 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.
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.
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.
A single adult male Western Grapeleaf Skeletonizer (Harrisina metallica) was found in late June 2018 in a vineyard trap in Calistoga. 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. The Napa County Agricultural Commissioner’s Office requests that growers and employees become familiar with this destructive pest’s appearance and behavior.