Sonoma county agricultural inspectors have found a mass of eggs and the nymph of a glassy-winged sharpshooter. This bug is an insect similar to a grasshopper and is associated with vineyard disease that can be devastating. An inspector by the name of Travis Howard with the Sonoma County Department of Agriculture found the infestation in a shipment of local citrus plants that came from Ventura County. Something similar was found the day previous, in a shipment from Santa Barbara County to Marin County. Area vineyard managers are not worried about the pests or the disease. This is because efforts to manage the threat have been aggressive by local agricultural authorities.
This pest, known as a glassy-winged sharpshooter, is a well-known carrier of Pierce’s disease. This is a bacterial infection that can rapidly destroy and entire vineyard, a devastating blow. A 2014 estimate relayed that Pierce’s disease has cost the state’s wine enterprise about $104 million per year. The glassy-winged sharpshooter is widely found in Southern California, and there is a cousin to this pest known as the blue-green sharpshooter, whose destruction can be found largely on the North Coast. All sharpshooters are leafhoppers and plant feeders that suck the sap from trees, shrubs, and grass.
The glassy-winged sharpshooters only get about half an inch long at its adult stage. Dark brown or black in color, they have black and yellow undersides, yellow eyes, and the upper part of the head and back are spotted with ivory or yellow specks. Their wings are transparent with veins that are reddish in color. These bugs lay their egg masses on the undersides of leaves, and cover them with a secretion that is white and powdery to protect them. After hatching, the egg mass leaves the leaf with a brown mark on the surface. These nymphs then feed on the small stems vascular systems on the plants that their egg mass was laid on.
In the mid 1990’s, there was widespread devastation of vineyards in Temecula, Riverside County caused by the glassy-winged sharpshooter. This invasion caught the attention of authorities for the state’s agricultural department. Sharpshooters spread Pierce’s disease by feeding on the vegetation and injecting a microorganism into the tissue of the grapevine. This results in dehydration of the plant, eventually becoming fatal.
The microorganism XylellaFastidiosa can also be found in oleander and citrus trees, which are both used sometimes in the landscaping of vineyards. Anytime a nursery shipment is received from southern California to places like Sonoma and Marin, there must be a notice that the items must be inspected by the county’s agricultural department before the items are put for sale. When an infestation is found, the entire shipment is placed back on the truck and sent back their place of origin in the southern region of the state.
The blue-green sharpshooter has made Pierce’s disease present in Sonoma County, usually occurring on a manageable scale. Vineyards that are located next to creeks and streams are more prone to an outbreak of this pest, as they prefer riparian habitats. Sangiacomo Family Vineyards has agreed; stating that the small outbreak they have had, was nothing that couldn’t be taken care of. A group of grape growers voted in June to continue assessment on wine grapes, funding research on Pierce’s disease as well as other pests that threaten the state’s wine grapes.
Since its inception in 2001, the assessment has raised over $32 million, currently at 75 cents per $1,000 value of grapes for wine. This research is partially aimed at developing vines that are disease-resistant. Muscadine vines are resistant to the disease, while chardonnay and pinot noir vines are extremely susceptible to it. Over the last century, rootstock resistance has helped suppress phylloxera infestations in the United States as well as Europe. Other parts of the research include supporting inspection programs, like the one in Sonoma County which has been extremely effective.
Though officials are skeptical about being able to completely eradicate Pierce’s disease, being able to contain it through inspection programs and research is key to controlling the infection. Growers hold value in the program, thus the sharpshooter has been prevented from becoming established in the southern portion of the state.