The California Dept of Food and Agriculture site for glassy-winged sharpshooter maintains an updated site on news and guidelines.
The California Farm Bureau Federation maintains a site on recent developments relative to the glasy-winged sharpshooter.
Distribution: Southern United States and northern Mexico except in very arid areas. Range recently extended into southern and central California.
Description: Adults about 1/2 inch (13-14 mm) long, dark brown color with small yellow dots on head and thorax. Wings membranous, translucent, with reddish veins.
Summary:
A new Pierce's disease vector, the glassy-winged sharpshooter (GWSS), has recently become established in California. This new vector is a serious new threat to California vineyards because of its faster and longer distance movements into vineyards. It may also increase the rate of disease increase by moving the causal bacterium from vine to vine. It inhabits citrus and avocado groves and some woody ornamentals in unusually high numbers. At immediate risk are vineyards near citrus orchards.
The glassy-winged sharpshooter (GWSS, Homalodisca vitripennis) has now become a major factor in Pierce's disease and how California growers will deal with the problem. At the very least, major headaches are ahead for grape growers who have until now had no problems with Pierce's disease.
From 1990 to 1994, GWSS was mistaken for a closely similar California species, the smoke tree sharpshooter (Homalodisca lacerta). What was unusual about GWSS was that it developed huge populations on citrus, crepe myrtle, avocado and several other species of woody ornamentals. GWSS is so abundant on citrus and some other plants that the residue from its excrement gives the trees on which it feeds a "whitewashed" appearance. This has alarmed citrus growers and homeowners, but so far the insect does not seem to be doing any direct damage to these plants, other than cosmetic damage to citrus fruits from egg masses deposited into fruits when populations of GWSS are high. This increases the danger of having a strain of Xylella fastidiosa bacteria that causes a serious citrus disease in Brazil arrive in California because the state now has an abundant vector on citrus. Because it feeds more often on oleander than other sharpshooters, GWSS is probably a major factor in the spread of oleander leaf scorch disease, which is caused by a newly introduced strain of Xylella fastidiosa.
GWSS has been seen in high numbers in citrus along the coast of southern California since the early 1990s. During the past few years it has become locally abundant further inland in Riverside and San Diego counties. In 1998 and 1999 high populations on citrus and adjacent vineyards were seen in southern Kern County. GWSS will spread north into the citrus belt of the Central Valley and probably will become a permanent part of various habitats throughout northern California. There is no reason to believe it will not become established along the coast and inland at least as far north as southern Mendocino County.
GWSS probably first entered California as eggs on plants. The eggs are deposited into plant tissues. GWSS was first collected near Irvine in 1989 but not recognized as a newly introduced species until later. The leafhopper was identified (Calif. Dept. of Food and Agriculture) as a species common in the southeastern states from Florida through eastern Texas that occurs as far north as Missouri. GWSS is considered the prime vector of the bacterium Xylella fastidiosa to peach and grape in Georgia, Florida, and other southern states. These plant diseases are most common from central Florida to the immediate area near the Gulf of Mexico and the coastal plain of Georgia and South Carolina. Cold winter climates are hypothesized to limit the geographic distribution of the diseases (phony peach disease and Pierce's disease of grapevine).
Phil Phillips, U. C. Area IPM Advisor at Ventura, California, notes that H. coagulata breeds on citrus in spectacular numbers in some groves. He has recovered resident parasitic wasps from the eggs of the glassy-winged sharpshooter.
The newly introduced GWSS is an efficient vector of Xylella fastidiosa to peach and grape in Florida and Georgia. It may become equally as important in California. If GWSS becomes widely abundant in northern California, GWSS could dramatically change the current patterns of Pierce's disease (PD) and of almond leaf scorch in the state. PD now is important in "hot spot" vineyards in coastal California and a few vineyards in the Central Valley. Periodically, major epidemics of PD occur for unknown reasons. A succession of wet winters is thought to trigger epidemics by increasing vector insect populations. A severe epidemic seems to be underway in Napa, Sonoma and Mendocino counties. A major PD epidemic has not occurred in the Central Valley since the 1940s, but the disease damages a few vineyards every year in the Central Valley. Almond leaf scorch disease has not been a major problem in California's main almond producing regions and was not seen at all in the southern Central Valley until the early 1990s. Unlike long-established insect vectors of Xylella fastidiosa, GWSS seems to feed on stone fruits during the dormant and early growing seasons. This could pose a very big threat to California's almond industry if GWSS begins to change the incidence of almond leaf scorch.
GWSS is a serious new threat to California vineyards because of its faster and longer distance movements into vineyards. This would more than offset its lower transmission rate of Xylella fastidiosa to grape compared to some established vector species. Because the glassy-winged sharpshooter feeds much lower on the cane than other sharpshooters in California, late season (after May-June) infections introduced by the glassy-winged sharpshooter may survive the winter to cause chronic Pierce's disease. This would enable vine-to-vine spread of Pierce's disease, which has not been the case in California. If t occurs, vine-to-vine spread can be expected to increase the incidence of Pierce's disease exponentially rather than linearly over time, as has been normal for California vineyards affected by Pierce's disease.
The glassy-winged sharpshooter also feeds on dormant grapevines during the winter. Until more information about this aspect of glassy-winged sharpshooter's role in spreading Pierce's disease is available, growers should try to reduce numbers of glassy-winged sharpshooter present in vineyards at any time. Additionally, removing diseased vines as soon as possible when Pierce's disease first appears in a vineyard may help reduce the infection rate. Early and vigilant disease detection and removal is recommended for any vineyards that experience influxes of the glassy-winged sharpshooter.
GWSS is expected to spread north into the citrus belt of the Central
Valley and probably will become a permanent part of various habitats
throughout northern California. It feeds and reproduces on a wide
variety of trees, woody ornamentals and annuals in its region of
origin, the southeastern United States. Crepe myrtle and sumac are
especially preferred. It reproduces on Eucalyptus and coast live oaks
in southern California.
To see the contents of an informational brochure, go to:
http://danrcs.ucdavis.edu/special/gwss/default.shtml
For more on the Glassy-winged Sharpshooter please follow these links:
http://ucceventura.xlrn.ucsb.edu/IPM/IPMHome.htm
http://acwm.co.la.ca.us/scripts/glassyW.htm
Prepared statements of testimony on the glassy-winged sharpshooter by two University of California researchers, Alex Purcell and Richard Redak.