Feared Pest Returns To California Vineyards
October 21, 2011 An old nemesis of California grape growers is back. About a decade since the glassy-winged sharpshooter was first found in Golden State vineyards, the pest, and the fatal Pierce’s disease (PD) it spreads, is back on the front burner.
In the past couple of months, the pest has migrated from Fresno’s residential areas to west Fresno County commercial vineyards, says Stephen J. Vasquez, Fresno County University of California Cooperative Extension. “We’ve had other pests come through, such as light brown apple moth and European grapevine moth, and we’d started to forget about glassy-winged sharpshooter and Pierce’s disease,” says the viticulture farm adviser.
PD dropped off the radar of valley grape industries and growers partly, as Vasquez noted, because of other invasive grape pests, including the vine mealybug, inhabiting vineyards, but also to a low incidence of PD found throughout the valley. However, in recent months glassy-winged sharpshooter (GWSS) has been trapped not only in west Fresno County commercial vineyards but also near the San Joaquin River.
The recent catches are a concern because they have been found near a major riparian corridor that has had a historically low level of PD, says Vasquez. With these recent GWSS catches, growers should survey their vineyards and test grapevines displaying PD-like symptoms in order to minimize potential “hot” spots from developing should GWSS become established.
Four PD symptoms growers/scouts should be on the lookout for:
– Scalded leaves, yellow or red margins
– Leaf blades drop, leaving petioles attached
– Irregular wood maturity (green/brown patches)
– Fruit shrivels or raisins prematurely
“Growers should definitely familiarize themselves with these symptoms, because PD can be confused with nutrient deficiencies, or diseases such as grapevine measles, or vines that simply look water stressed,” says Vasquez. “If you see all four symptoms, that’s a red flag: Let’s get this tested.”
For more information, go online to: http://anrcatalog.ucdavis.edu/
Subscribe Today For
