Two small populations of Virginia creeper leafhopper have been confirmed in Napa County, bringing to three the number of California counties where this invasive pest has been found.
The other two are Lake and Mendocino counties, according to a University of California Extension newsletter.
The two small populations in Napa County are in the Pope Valley and St. Helena.
Despite their name, the pests also feed on winegrapes, raising concern among North Coast winegrape growers.
The newcomer can be told from the resident Western grape leafhopper by its four red dots on its thorax. The Western grape leafhopper has yellow spots.
Damage from the Virginia creeper leafhopper can include complete vine defoliation if left untreated.
Although the Western grape leafhopper is controlled in many areas of the state by natural enemies, none has been found so far that parasitizes Virginia creeper leafhopper eggs.
To view a UC video on how to differentiate the two, visit http://cesonoma.ucanr.edu.