“I’ve been telling growers that it’ll be sometime after the 2016 harvest,” he said.

The EGVM is a yield-robbing pest affecting grapes that has, in extreme cases, destroyed entire grape crops.

According to the University of California (UC), Lobesia botrana (EGVM)  was first reported in the United States in Napa County in Oct. 2009. Native to Southern Italy, it was first described from Austria and is now found throughout Europe, North and West Africa, the Middle East, and eastern Russia.

It was more recently introduced into Japan, and in 2008 was reported in Chile.

In May and June, first-generation larvae web and feed on the flower clusters. Second-generation larvae (July-August) feed on green berries. Young larvae penetrate the berry and hollow them out, leaving the skin and seeds.

Third-generation larvae (August-Sept.) cause the greatest damage by webbing and feeding inside berries and within bunches, which become contaminated with frass (excrement).

Additionally, feeding damage to berries after veraison exposes them to infection by Botrytis and other secondary fungi such as Aspergillus, Alternaria, Rhizopus, Cladosporium, and Penicillium. Secondary pests such as raisin moth (Cadra figulilella), fruit flies, and ants may also be attracted to damaged berries, UC reports.

Within a year of discovering the pest in Napa County, officials had trapped over 100,000 EGVM.

How the moth arrived in Napa County, home to some of California’s premiere wines, is still a mystery.

“One of our concerns is we don’t know how it got here,” Clark said. Knowing how it got there could be important to preventing further introductions to this and other invasive pests.

As fast as the EGVM appeared and reproduced it seems to have dwindled in numbers in equal fashion. In 2011 officials trapped 113 EGVM. That number fell to 77 in 2012 and 40 in 2013.

There have been no finds since Jan. 1, 2014.