May 25, 2022
Grapevine pest found in California wine county

Napa County, California, agricultural officials are asking growers to be alert after a single adult western grapeleaf skeletonizer, a “voracious” eater of grape leaves, was found in a major wine production area.

The pest was found in a trap by insect trapper Jesse Guidi on May 12, according to the Napa County Agricultural Commissioner’s Office. Agricultural Commissioner Tracy Cleveland said the western grapeleaf skeletonizer is a “destructive and serious” pest and growers and gardeners should watch for all larval (caterpillar) stages of the moth.

“All larval life stages are voracious feeders that cause extensive

The larval stage of the western grapeleaf skeletonizer. Photo: University of California-Div. of Agriculture and Natural Resources

damage to grape leaves, including partial or complete defoliation of grapevines,” Cleveland said in a news release. “Excessive feeding can damage fruit and lead to secondary fungal damage. We do not want this pest to become established in Napa County.”

Guidi found the western grapeleaf skeletonizer in a yellow-panel sticky trap used to monitor the glassy-winged sharpshooter, another pest that’s harmful to grapevines. The agricultural commissioner’s office added 25 traps within a mile radius of the pest finding near Dollarhide Road, Pope Valley.

The pest is not native to Napa County, but has been detected there in the past, most recently in the same area in June 2018.

The western grapeleaf skeletonizer leaves only the veins of leaves behind when feeding, leaving a distinctive, lacy skeletal appearance, according to the agricultural commissioner’s office.

It can also be found on Boston ivy and Virginia creeper. The larval stage is distinguished by colored bands around the body. For more information and photos, visit the University of California Integrated Pest Management website.

County agricultural officials are asking growers, vineyard managers and others who are moving farm equipment or winegrapes into Napa County to inspect them for western grapeleaf skeletonizer and other pests.

“If you suspect you may have found a western grapeleaf skeletonizers caterpillar or adult moth, please bring it in to our office immediately, or contact us in order to help identify it,” Cleveland said in the release.