The European grapevine moth, or EGVM, remains a threat. Early-summer monitoring programs, however, are very encouraging, though the moth is a secondary threat to other crops.
The moth prefers grapes, but it will feast on olives, prunes, peaches, plums, cherries, etc.), kiwi, pomegranate, and more, as well as some ornamentals. According to the USDA, the moth can also live on blackberries, currants, jujubes, persimmons, St. John’s wort, rosemary, carnations and red clover.
• EGVM prefers grapes, but will feast upon olives, prunes and other foods.
• First trapped in Napa County, the moth has spread to several counties.
• Numbers of EGVM moths CDFA inspectors are seeing are a real cause for optimism.
While EGVM was first found in one area of Napa County, the spring statewide monitoring turned up moths in Solano, Mendocino, Merced, and Fresno counties. One moth was found in the Monterey area, but no additional moths were found.
When discovered, California Department of Food and Agriculture immediately implemented quarantine areas in five-mile zones around multiple moth discoveries. The federal government followed suit. The quarantine zones are in the Napa Valley near Rutherford, but also include areas in Sonoma, Mendocino, Solano, Merced and Fresno counties. The quarantine zone in Fresno County is 96 square miles; Merced, 108 square miles; Mendocino, 179 square miles; and Napa/Solano/Sonoma counties, 1,233 square miles.
“Producers mounted an aggressive treatment program, especially in the Napa Valley,” says Larry Hawkins, a USDA spokesman. “And it seems to be working. The second generation is starting to hatch now, and we are seeing a dramatic decrease in the number of insects.”
Fresno area grape grower Brett Bonomi is relieved, but not surprised, that the moth was quickly and easily controlled. Bonomi grows winegrapes within the Fresno County quarantine area, and he hauls his grapes to a winery in the quarantined area.
“At first we were very nervous. But we learned that its life cycle and habits were very similar to insects we already spray for,” Bonomi says. We haven’t seen any of these moths and hope we never do.”
The European grapevine moth is a worldwide threat; it has been found in Europe, southern Asia, the Caucasus region of Russia, Japan, the Middle East, the Near East, South America and western Africa. The third generation is the most damaging. It feeds on multiple ripening grapes and exposes them to further damage from fungal development and rot. The larvae overwinter as pupae in protected areas under the bark; then the pupae emerge as adults in the spring.
Organic growers are worried, and fearful that the detection program will bring its own problems. One organic grape grower is so concerned about the potential for mealybug contamination that he issues clean tools to farmworkers and requires them to come to his field in clean clothes before working at any other fields.
“I’m worried about these inspectors going from vineyard to vineyard, bringing bugs in from other fields,” the grower, who did not want to be identified, says. “If they were to bring mealybug into my organic vineyards I’d be out of business.”
“We address these concerns,” Hawkins responds. “In Fresno, all of the traps are on the perimeter of the vineyards, and we do not have to enter the field. In Napa, we are including these traps with our mealybug monitoring program, and are taking precautions when we collect the trap.”
Grapes harvested within 200 meters of a location where a moth has been found will have to be fumigated before leaving the quarantine area. All growers in the quarantine areas have been or will be asked to sign a compliance agreement outlining how crops, vehicles and equipment will be treated during the quarantine. The quarantine includes homeowners, nurseries and landscapers.
It appears the fast action may have averted a major crisis. “We’re not at the peak yet for the second-generation hatching,” Hawkins says, “but the numbers we are seeing are a real cause for optimism.”
More is at www.cdfa.ca.gov/phpps/egvm/index.html.
Wilcox writes from Sanger.
This article published in the August, 2010 edition of CALIFORNIA FARMER.