Glassy-winged Sharpshooter (GWSS)

Definition - What does Glassy-winged Sharpshooter (GWSS) mean?

A Glassy-winged Sharpshooter (GWSS) is an agricultural pest native to the northern part of Mexico that has spread over North America to infect the US. A large leafhopper insect, it is a member of the Cicadellidae family and very similar in appearance to other sharpshooters.

The GWSS’s diet consists of over 70 different species of plant, which makes it the perfect carrier for Xylella Fastidiosa. This bacterium feeds on the xylem of the plant - the part of the vine that transports water, the way our veins transport blood. It is linked to several plant diseases, but in the context of vineyards, it is connected Pierce’s Disease.

WineFrog explains Glassy-winged Sharpshooter (GWSS)

Fully grown, the GWSS is 0.5 inches (12mm) in length with a dark brown to black body. The wings are transparent with reddish veins, and it’s underside is ivory and yellow. It has a piercing sucking mouth and rows of fine spines on its hind legs.

When feeding, the GWSS pierces the plant’s xylem and ingests the nutrients from the plant. That alone, if done multiple times and by a hoard of GWSSs, could damage the crop, since the nutrients meant for the plant’s leaves and life are consumed by the insect instead. However, as a carrier for the Xylella Fastidiosa bacterium, the GWSS is a greater threat to the agricultural ecosystem.

In the case of Pierce’s Disease, Xylella Fastidiosa creates a gel in the xylem tissue over time, preventing water from moving up the vine. The leaves turn yellow and brown, falling off the vine; shoots die. After one to five years, the vine dries up completely and dies. A similar process is experienced in other plants, though with different effects.

GWSS is a serious threat to California’s vineyards because the insects are able to move faster and travel further distances. The GWSS feeds lower on the vine and for longer in the season, which means that the infections introduced later in the season may survive the winter to cause chronic Pierce’s Disease. Chronic Pierce’s Disease enables vine-to-vine spread and causes exponential transmission of the disease in a vineyard plot.

The agricultural governments are working on a cure for Pierce’s Disease, though the current policy is prevention. Wine growers are instructed to monitor the vineyards, ridding them of the GWSS if possible and, if not, removing/destroying the infected vines immediately.
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