As the spring weather warms up and European grapevine moths (EGVM) emerge after a long winter, the invasive pest is increasingly turning up in traps set throughout California.

The detections have resulted in the addition of portions of Fresno and Mendocino counties to the EGVM quarantine. Current quarantine areas in Napa, Sonoma, and Solano counties have been expanded.

“We have set an array of more than 40,000 traps statewide to determine exactly where the infestations exist,” said A.G. Kawamura, secretary, California Department of Food and Agriculture.

“Detecting the pest is an important first step toward controlling it, and quarantines are the next step in the process,” Kawamura said. “These regulations allow us to protect surrounding uninfested areas by preventing movement of the insects on crops, harvesting equipment, and related articles.”

Previously quarantined areas in Napa, Solano, and Sonoma counties are expanding by approximately 827 square miles.

New quarantine areas are being created in Fresno County (approximately 96 square miles) and in Mendocino County (approximately 140 square miles).

California’s total EGVM quarantine area now stands at about 1,395 square miles.

Maps of the quarantined areas are available online at: www.cdfa.ca.gov/phpps/PE/InteriorExclusion/egvm_quarantine.html.

The quarantines primarily affect farmers plus those who harvest, transport, and otherwise process or handle crops. Agricultural officials have begun informing those involved in the industry of the requirements.

These people generally sign compliance agreements that indicate how crops, vehicles, equipment, and related articles are to be treated during the quarantine, CDFA says.

Homeowners, plant nurseries, landscapers, and other citizens and businesses who work with plants are also involved in the quarantine. Residents who have grapes, stone fruit trees (peaches, plums, etc.) and other “host plants” for this pest in yards are asked to harvest and consume the fruit on-site to further limit the risk of spreading the pest.

Residents in quarantined areas are asked to review the list of host plants/fruits (below) and to not remove them from their property. The produce may be harvested and consumed on site.

EGVM, Lobesia botrana, is found in southern Asia, Japan, Europe, North Africa, Anatolia, the Caucasus, and in South America.

The pest primarily damages grapes, but also feeds on other crops and plants

The EGVM larvae, not the adult moths, are responsible for the damage to grapes. Larvae that emerge early in the spring feed on grape bud clusters or flowers and spin webbing around them before pupating inside the web or under a rolled leaf.

If heavy flower damage occurs during this first generation, the affected flowers will fail to develop and yield will be reduced Second-generation larvae enter the grapes to feed before pupating in the clusters or in leaves.

Larvae of the third generation – the most damaging – feed on multiple ripening grapes, exposing them to further damage from fungal development and rot. The larvae overwinter as pupae in protected areas including under the bark, and emerge as adults the following spring.