Area-wide treatments coordinated by the U.S. Department of Agriculture (USDA) have largely kept populations of glassy-winged sharpshooter (GWSS) in check. Containment efforts on behalf of state and federal officials were implemented to curb the pest’s ability to spread Pierce’s Disease in vineyards. The management program has primarily focused on Fresno, Kern, Madera, Riverside, and Tulare counties.
“For those grape growers that are on the ground in areas in the San Joaquin Valley living with glassy-winged sharpshooter, we’re really trying to help them lessen the impact of the insect moving that disease around their vineyards and them losing vines,” said Beth Stone-Smith, California Assistant State Plant Health Director with USDA. “The secondary piece is trying to stop the pest itself from moving further in California.”
The insect is a large leafhopper with numerous hosts and a strong ability to fly. Citrus is one the most predominant hosts for GWSS aside from grapes and nearly 25,000 acres of citrus trees were treated as part of the program in the Southern San Joaquin Valley in 2019. Stone-Smith noted that a multitude of factors has to be considered when making area-wide treatments, which requires a great deal of planning and coordination. “It can come down to the different soil types depending on the area we’re trying to treat and the timing of that treatment in the insect’s biology,” said Stone-Smith.
Field staff are continually monitoring temperature data, trap detections, and GWSS populations to help keep treatment coordinators up to date with field conditions. Winter temperatures play a critical role in how GWSS populations develop. With recent winter temperatures being fairly close to average it should prevent any extra generations from developing in 2020. After nearly 20 years of the area-wide treatments, it appears that the program has been successful in preventing the pest from moving further north.
“Researchers, in the beginning, didn’t believe that we would be able to hold the line as long as we have and that really comes down to the coordination, the people involved, and really industry and growers telling us that it matters to them,” Stone-Smith noted. “So, I continue to try and fight to hold that line.”