In 1999, about one-third of the vineyards in Temecula Valley, Riverside County, California were destroyed due to Pierce’s Disease which is caused by a bacteria transmitted to grapevines by an insect-the glassy winged sharpshooter. The disease seemed destined to spread throughout Southern California. However, research demonstrated that a carefully-timed insecticide application would prevent the sharpshooter from transmitting the disease to grapevines. As a result of this insecticide use, the wine grape industry in Southern California has recovered and is prospering.
“Twelve years ago a Pierce’s disease epidemic in Southern California wine grapes prompted a multi-pronged local, state and federal attack to contain the disease spread and find a cure or treatment.
Riverside County agriculture officials declared a local emergency in 1999 and 300 acres of Temecula wine grape vines were destroyed after they were found to be infested with the glassy winged sharpshooter.
Emergencies were declared, a task force was formed, and in 2000 $22.3 million in federal financial assistance was secured to reduce pest infestations and support research.
Research found that the Southern California epidemics were almost entirely the result of vine-to-vine transmission…. A protocol of applying one carefully timed application of a persistent systemic insecticide such as imidacloprid virtually eliminates the vine-to-vine spread.
Ben Drake is a Temecula-area wine grape grower and vineyard manager who began seeing problems from PD in the Temecula Valley as early as 1997.
We’ve found that if we apply (imidacloprid) at the middle to the end of May, before the sharpshooter moves out of the citrus and goes into the vineyards, we get levels of the material into the plant high enough that when the sharpshooter flies over from the citrus groves to try it, they just fly back where they came from. Or, if they feed long enough, it will kill them.
But just look at the Temecula Valley now to understand what’s changed: From 12 wineries in 1999, the Temecula Valley Winegrowers Association website today lists more than 50 growers and 34 wineries…. A thriving agritourism industry has developed…. Existing wineries are expanding and new ones are under construction or in planning phases.”
Author: Christine Thompson
Title: Grape growers urged to remain vigilant against sharpshooter pest
Source: Western Farm Press. 2011-12-12. Available at: http://westernfarmpress.com/grapes/grape-growers-urged-remain-vigilant-against-sharpshooter-pest