Deadly pest detected in Californian citrus groves
An invasion of glassy winged sharpshooters which carry a disease deadly to grape vines has been detected in orange groves in Temtecula in California,
The pests which devastated the region in the late 1990’s, carry Pierce's Disease which kills not only vines but many other of California's crops.
Scientists monitoring the region said they had trapped more than 1,500 of the pests last month in the groves, the largest haul since a trapping programme was started in 2003.
“It’s certainly very scary,” UC Riverside scientist Matt Daugherty told the Press Enterprise, adding that the previous recorded high for the region was in 2008 when around 1,000 of the insects were detected.
In the late 1990’s grape growers in the region had around 3,500 acres of vineyards, but that plummeted to only 1,000 acres in the wake of the sharpshooter plague which left grapevines dehydrated due to the baceterium the insects carry. Those growers who survived the invasion adapted, and planted new, hardier varietals. However, the total vineyard acreage is still not what it was at its peak, at a current 1,800 acres.
Growers have attributed the return of the sharpshooters to the winter storms that revived some citrus groves that had been fallowed during the drought. When the rain fell, the water injectd life into untreated trees and provided a fertile breeding ground. “They respond positive to warmish and wet winters and springs,” Daugherty said. “It’s really plausible the big influx of rain could have kicked off a new production.”
Others blame the return of the scourge on the state's decision three years ago to cut funding for spraying of orange groves which specifically targeted sharpshooters.
Meanwhile the Temecula Valley Winegrowers Association’s viticulture committee is putting together proposals for trapping and spraying and will be distributing the plan to growers in the area.
“The uptick isn’t an imminent threat to the vineyards yet, it’s an early indicator that we may have an issue later,” said Greg Pennyroyal, vineyard manager for Wilson Creek Winery. “It’s urgent that we act now so we can avoid catastrophic problems.”