On May 12, insect trapper Jesse Guidi discovered a single adult Western Grapeleaf Skeletonizer in an insect trap near Dollarhide Road, Pope Valley. That is why Napa County Agricultural Commissioner Tracy Cleveland is asking growers and gardeners to watch for all larval stages of this moth.
Cleveland: “This is a destructive and serious pest. All larval life stages are voracious feeders that cause extensive damage to grape leaves, including partial or complete defoliation of grapevines. Excessive feeding can damage fruit and lead to secondary fungal damage. We do not want this pest to become established in Napa County.”
Although the pest is not native to Napa County, it has been found here a number of times in the past, most recently in the same area adjacent to Tubbs Lane in June 2018. Native to Arizona and New Mexico, it was first discovered in California in the 1940s and eventually spread throughout the state, particularly in the Central Valley.
Damage caused by the Western Grapeleaf Skeletonizer is relatively easy to detect. When it feeds on grapevines, it leaves only the veins behind, producing a very distinctive, lacy skeletal appearance.