What is in this article?:
- California's strategy for slowing or stopping the spread of the GWSS and for finding solutions to PD has been so successful that growers sometimes get lulled into complacency.
- Southern California epidemics were almost entirely the result of vine-to-vine transmission.
- Uptick in PD discoveries in southern Kern County, Calif., alarming.
UC Riverside Extension entomologist Nick Toscano, right, watches at Temecula-area wine grape grower and vineyard manager Ben Drake, left, checks one of 450 sticky GWSS traps in Temecula with one of his employees Jim Hakrey.
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. Today, the Pierce’s Disease/Glassy Winged Sharp Shooter Control Program is lauded as a highly successful model of results-driven cooperation between government agencies, citrus growers, nurseries and wine and table grape growers, university researchers and industry stakeholders.
Programs to control the Asian citrus psyllid/Huanglongbing and European grapevine moth follow its model. It has been expensive. $438.5 million has been spent so far.
Disease management protocols developed through the program have virtually eliminated vine-to-vine transmissions by the glassy winged sharpshooter (GWSS), the insect vector of Xylella fastidiosa, the bacterium that causes Pierce’s Disease — as long as growers stay alert and maintain best management practices. Area-wide programs fund monitoring, biological controls and insecticide treatments in citrus groves that harbor the GWSS. Grower assessments have supported fast-track research that identified plant hosts, led to development of PD-resistant vine varieties and discovery of compounds within the plants that appear effective at stopping or reducing the symptoms of the disease.
It could have been much different.
Paul Giboney graphically describes recognizing the widespread devastation that could be wrought by Pierce’s disease fully infecting his Kern County table grape vineyards. “We felt like we were standing in a pool of gasoline just waiting for the match to get lit,” he said.
Giboney and others from around the state had traveled to Riverside County to witness for themselves the ground zero of a disease that with amazing ferocity had gotten a stranglehold in Temecula Valley vineyards. 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 GWSS.
Within a year or so, Giboney and other Kern County growers were seeing vines dying in pockets in the Arvin and General Beale areas, and it “looked like the handwriting was on the wall.” These outbreaks were much more severe than California’s traditional patterns of PD.
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. The state Pierce’s Disease Control Program was officially established. Survey protocols and guidelines to use for finding infestations were created. A website dedicated to Pierce’s disease and the GWSS set up by the California Department of Food and Agriculture received 500,000 hits in its first year online.