Keep an Eye Out for the Glassywinged Sharpshooter!
As you may know Glassy-winged Sharpshooter (GWSS) was found in the Browns Valley Neighborhood of Vacaville in October of 2021. The Solano County Department of Agriculture, under the direction of the California Department of Food and Agriculture, is conducting an eradication program to eliminate GWSS from the area. My day job is as a biologist for Solano County Ag department and most of my time is being spent on this project.
GWSS is an insect native to the southeastern United States that made its way to Southern California in the late 1980's to early 1990's. It is well established in Southern California and over the years has hitchhiked into Northern California 13 times on plants coming from infested areas. Those introductions were all eradicated using a similar protocol to the one now being used in Vacaville.
GWSS are of concern because they can vector a bacteria called Xylella fastidiosa (Xf). In grapes, Xf causes a fatal disease called Pierces Disease. Other strains of Xf vectored by GWSS cause disease of oleander, almonds, alfalfa, citrus and potentially oaks, elms, maples and sycamore. GWSS is an aggressive flyer and can move Xf farther and faster than native sharpshooter vectors. Integrated Pest Management programs can keep GWSS populations suppressed, but only a few individuals are needed to vector disease. That is why eradicating them where possible is the best option.
GWSS have been found on 76 residential properties all within a mile of each other. The treatment protocol is to treat the infested property and any property within a 300 ft radius of the find in order to contain and kill any insects that escaped detection. The treatments consist of a soil injection of imidacloprid insecticide which is taken up systemically by the host plants. In 2022 we treated 916 properties. Adult GWSS finds in October-December 2021 were 86 adults, after treatments the number of adults during the same period in 2022 were down to 8 adults.
In addition, the state was able to release beneficial insects that parasitize GWSS eggs. They will reduce the number of eggs surviving but never eradicate GWSS completely.
The plan for 2023 is to repeat treatments on the 916 properties and any new properties if GWSS is found there. For those of you in Browns Valley, if we have not already met, you might find me knocking on your door this spring!
Adult GWSS are ½ inch long. Eggs are laid on the underside of leaves in masses about 1 inch long. Nymphs are a dull gray color. Links to more information, and a video clip we made of eggs hatching:
photo by Jack Kelly Clark. An adult glassy-winged sharpshooter, Homalodisca vitripennis, next to whitish wax on the leaf surface, which marks where the female inserted her egg cluster into tissue.