Glassy-Winged Sharpshooter

Glassy-winged sharpshooters are large leafhoppers—about one-half inch long. They have a flat triangular shaped head and large eyes. They spread Pierce's disease when they feed on grapevine. Here's what to look for:

• Immature branches
  • New branches don't mature properly. Patches of green, or "green islands," surround mature brown bark. Symptoms gradually spread along the immature branches, from the point of infection toward the tip of the plant, and more slowly towards the base. Tips of new branches and roots may start to deteriorate.
• Discolored leaves
  • Along the edges, leaves turn slightly yellow or red and eventually dry or die, leaving circle patterns.
• Shriveled and clustered grapes
  • Grapes wilt and dry, or "raisin up," before harvest time. By mid-season, some or all fruit clusters on the infected branches may wilt and dry.
• Matchsticking
  • Leaves fall prematurely. However, their leafstalks remain, making them look like green matchsticks.

Note: You may not see all four symptoms in diseased grapevines.

To prevent further spread of the glassy-winged sharpshooter and the bacteria it spreads, growers and others should:

• Rouge/remove infected vines
• Ensure plants, especially nursery stock and citrus, are inspected before they are moved from southern California to another part of the State

There is no treatment for Pierce's disease. Once a grapevine shows signs of disease, it must be removed and destroyed to stop the spread. This is critical to help reduce infection rates.

The probability of vines recovering from Pierce's disease depends on several factors, including:

• When the plant was infected
• Temperatures in the winter following infection
• The variety's tolerance to Pierce's disease

Recovery is unlikely if disease symptoms are present in the same growing season the plants were infected. This is especially true for varieties that are very susceptible to Pierce's disease, such as Santa Barbara Pinot Noir or Chardonnay.