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Glassy Winged Sharpshooter

Recently I was conversing with some colleagues at the nursery about some oleanders I wanted to train into trees for landscaping. Since they know I have a small vineyard, they brought to my attention that oleanders were a host for the glassy-winged sharpshooter. So of course, my ears popped up and with all the news flashes lately, I didn't want to promote an infestation that I could avoid. It also stirred up my curiosity of what other plants might host this pest, what it actually does, and how to prevent it, because to be truthful, I was not that informed on the glassy-winged sharpshooter So I contacted our local county experts for their information. The following is derived from the University of California Pierce's Disease Research and Emergency Response Task Force pamphlet on the glassy-winged sharpshooter and some additional input from Cindy Fake.

The glassy-winged sharpshooter (Homalodisca coagulata) has been a serious pest in California for over a decade.  Native to the southeastern United States, this insect was first observed in California in 1989 and is now found throughout Southern California and Kern County. It is a particular threat to California vineyards due to its ability to spread Xylella fastidiosa, the bacterium that causes Pierce's disease. Pierce's disease kills grapevines, and there are no known treatments for it.  Glassy-winged sharpshooters caused a Pierce's disease epidemic in the Temecula region of Southern California in the late 1990's that threatened the survival of its viticultural industry. 

In addition to Pierce's disease, X. fastidiosa causes almond leaf scorch, alfalfa dwarf, oleander leaf scorch, and citrus variegated chlorosis. The potential spread of these diseases by the glassy-winged sharpshooter should be of concern to agricultural producers throughout California.

The glassy-winged sharpshooter feeds on a wide variety of ornamental and crop plants. On most plants, it feeds on stems rather than leaves. When feeding, it excretes copious amounts of watery excrement in a steady stream of small droplets In urban areas, this "leafhopper rain" can be a messy nuisance. When dry, the excrement can give plants a whitewashed appearance.

A large insect - almost ½ inch (12mm) long - the glassy-winged sharpshooter is dark brown to black with a lighter underside. The upper parts of the head and back are stippled with ivory or yellowish spots; the wings are partly transparent with reddish veins. Watery excrement often collects on either side of the insect, appearing as large white spots.  Pictures of the insect are at the UC Davis Integrated pest management site

Early detection of the glassy winged sharpshooter in Central and Northern California is important for developing control strategies. Growers can be of great assistance in this effort. Yellow sticky traps, even those used to detect other insects such as apple maggots or blue-green sharpshooters, are useful for monitoring the glassy-winged sharpshooter.  Plants can be examined by direct observation or by using a sweep net. Look for adult insects, nymphs, and egg masses.  If you find egg masses or insects you suspect to be the glassy-winged sharpshooter, contact your local UC Cooperative Extension office (Cindy Fake - (530) 889-7385) and/or your county Agricultural Commissioner (Christine Turner (530) 889-7372)).  They can help with insect collection and positive identification. Take them specimens, and note where and when they were collected and on which plants they were found.

Also included in the package sent was a list of hosts for this sharpshooter. The list was pages long and at least 25% of them I already had in my landscaping. Some of the most common plants were on this list, for example: the crape myrtle when leafed out, is an excellent host. In the Spring: euonymus and early stone fruits. In the Summer: apricot, carob, citrus, euonymus, grape, mulberry, plum, red bud, and sunflower. In the Fall: citrus and eucalyptus. And these are just me main hosts. The others are: from azalea to oak, from jasmine to phlox, and dogwood to redbud. We'd all have to have totally bare landscapes if we tried to prevent the infestation by removing the prime and additional hosts. One thing to note, having host plants in your yard does not mean you are likely to have an infestation; the pest has to get to you first.

I also spoke with Cindy Fake to find out if an infestation of Pierce's disease had come to Placer County She informed me that in the more than 100 years of wine grape production in Placer County, there has never been a Pierce's Disease outbreak. Although the disease has been in California for over a century and we have many native sharpshooter species that could transmit it, it has not been found in the foothills. However, the glassy-winged sharpshooter has been found in incoming agricultural shipments, which tells us how important it is to have every shipment inspected (and certified where applicable) to prevent incoming intruders. The California Department of Agriculture's inspection and quarantine program has resulted in containment of the sharpshooter vector to counties affected prior to 2003, and eradication in several counties with small infestations. She also said that phylloxera, the vine mealy bug, and the new gilli mealy bug were much greater threats to our vineyards then the glassy-winged sharpshooter at this time.

In summary, I don't plan on ripping out half of my woods and most of my landscaping to prevent the glassy-winged sharpshooter but I will keep an eye open for the creature and if found, let the county agricultural folks know.

For further information: U.C. Berkeley's An Introduction to Pierce's Disease or U.C. Davis pamphlet on the Glassy Winged sharpshooter (PDF) or our local county agricultural department with the numbers listed above. Also the California Department of Food and Agriculture Plant Quarantine Manual, Pierce's Disease Control Program: Sections 3650 through 3659 including Appendix A, Appendix B and the forward (page 510.1) - which encompass all California county restrictions on the glassy-winged sharpshooter.
My sincere thanks to Christine Turner and a special thank you to Cindy Fake for their assistance and input to this article.

Lynn E. Appell

 


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