Costly Fight Against Moth

Napa authority details value of grapes, wine lost to European grapevine moth

by Paul Franson
sonoma state wine education
The withering of Chardonnay berries was first documented mid-September 2009 in an Oakville, Calif., vineyard.
Napa, Calif.—At the recent Vineyard Economic Seminar, Greg Clark, the assistant agricultural commissioner for Napa County, described how local growers, ag advisors and agricultural regulators joined forces to defeat one of the biggest threats to grape crops in the county and the state, the European grapevine moth.

The withering of Chardonnay berries was first documented mid-September 2009 in a vineyard on Money Road in Oakville, Calif. Samples were collected, larvae found, and the culprit was positively identified by CDFA/USDA as Lobesia botrana—the European grapevine moth—that same month. It was the first discovery of the pest in North America.

By the end of October, the entire 11-acre Chardonnay crop, an estimated 65 tons of grapes valued at $163,816, was lost. The total loss to the winery, however, was $1,045,200, the potential value of wine, and this was just for a single property.

The county reported losses of 131 acres, representing 179 tons valued at $519,639, a wine value loss of $3,333,212.

Keeping tabs on EGVM
The European grapevine moth (EGVM) has three generations per year, and each insect goes through four stages: egg, larva (caterpillar), pupa and adult (moth). It feeds almost exclusively on the flowers and fruit of grapes; the first generation can feed on the flowers and fruit of olives, too.

More than 100,000 moths were trapped throughout Napa County in 2010, with the largest concentrations from St. Helena to Yountville in the middle of Napa Valley and on Third Avenue in Coombsville east of Napa.

Moths also were found north of Calistoga, in Napa and north Napa and in Carneros as well as all cities and towns in the valley.

In addition, the moths were found in many other counties of California, including Sonoma, Solano, Mendocino, Fresno, Merced, Monterey, San Joaquin, Santa Cruz and Santa Clara; quarantine was declared except in Monterey County, where only one was found.

Treatments were applied in 2011, after which EGVM was only found in Nevada, Santa Clara, Napa, Sonoma and Santa Cruz counties. In all, only 33 adult EGVMs were detected outside of Napa County in 2011.

In 2011, during the insects’ first flight, 96 moths were trapped and confirmed at 30 different sites, most in areas with high moth counts in the late part of 2010.

During the second and third flights that year, 17 more moths were trapped for a total of 113 moths in 2011, a 99.9% reduction from 2010.

The success reflects the efforts and cooperation of industry, federal, state and local government agencies, especially Monica Cooper, who was appointed the Napa grapevine farm advisor in 2009. Clark added that some reduction likely occurred from mating disruption, but most was due to spraying pesticides at the right times.

In 2012, 44 moths were trapped at eight locations during the moths’ first flight, and the hot spot appears to be Olive Hill Lane east of Napa in the Coombsville district. Moths were found at six separate properties in a 2-mile by 1-mile area, but the majority (35) were found at one property.

This area is a challenging environment with many homes, and workers made door-to-door visits, sent mailers and deployed higher trap densities. Mating disruption also was used. Single moths were found on Sage Canyon Road and Greenfield Road.

For 2011 and 2012, only the first and second generations were treated by recommendation of the Technical Working Group:

Isomate-EGVM mating-disruption pheromone was used in vineyards within 500 meters of a past find.

Vines were treated with synthetic or organic pesticides according to a degree-day model and before damage or EGVM was seen. Clark said that organic growers did the best job of properly timing pesticide applications in 2011.

The treatments in 2012 were the same as in 2011, but no mating disruption was used in Pope Valley and Chiles Valley.

Clark estimated the treatment costs in 2011:
Isomate pheromones
• Material: $85/acre/season
• Labor: $25/acre

Conventional synthetic chemical pesticides
• Materials: (mainly Intrepid and Altacor) at an average cost of $30/acre with three applications
• Labor: $25/acre per application
• Equipment: $65/acre per application
• 22,000 acres x $360/acre/season = $7,920,000

Organic chemical treatments
• Materials: (mainly Dipel and Entrust) at an average cost of $30/acre with six applications
• Labor: $25/acre per application
• Equipment: $65/acre per application

Regulatory and quarantine program
Clark said that the regulatory and quarantine program used to fight the moths was new and completely different. “It was a complex system compared to anything that had been done before.” Its purpose is to prevent the artificial spread of EGVM.

The quarantine provides for movement of winegrapes under compliance agreements that are required for anyone moving or receiving fruit, equipment or plant debris, within or outside of quarantine area. Specific forms were required for growers, haulers and wineries.

The quarantine can be removed if no EGVM finds are made for five generations, the last two of which cannot include use of mating disruption. To be safe, trapping densities were increased from 25 to 100 traps per square mile within 500 meters of a previous EGVM find.

More than 900 compliance agreements were issued by the county, which performed 200 inspections of growers, haulers, wineries and nurseries, some with the aid of the California Highway Patrol.

They also inspected 148 tons of grapes shipped out of the state, with 94 tons sent for fumigation and 54 tons shipped by a systems approach.

The estimated cost to the industry for compliance (sanitation, covering loads and slack filling of bins):
• Sanitation of farm equipment prior to moving off site: $3 million.
• Sanitation of bins in the field and at wineries: $875,000
• Labor and extra trucking from slack filling bins: $612,000

Outreach and education
The county developed a community relations plan with stakeholders as well. It conducted intensive outreach to community and industry.

• Grower meetings in Calistoga, Yountville and Napa
• UC Cooperative Extension and industry newsletters
• Grower liaison meetings
• “Kick the Moth Out” signs throughout the county; booths and displays at county fair; local media

Noncommercial, backyard and trellised grapes need to be repeatedly sprayed with an organic product such as Bt or spinosad or have flower and fruit clusters removed.

Urban/residential program
Urban treatments were started by CDFA in 2011:
• 1,300 pounds of grapes were removed from 82 properties;
• 131,281 mating disruption dispensers were deployed on a total of 1,651 properties;
• Fruit removal and mating disruption were employed at the vineyard plantings at the closed Copia facility and Napa County Airport and in Coombsville and along Imola in Napa.

Clark noted that funding is critical for detection and regulatory programs.

The county and others provided assistance to growers including cost sharing and/or provided more than 24,000 acres of mating disruption dispensers free of charge to growers within 500 meters of an EGVM find.

Mating disruption was funded by USDA ($1 million), Napa County ($326,000) and CDFA (provided 5,000 acres worth of mating disruption).

The ag office has authority for mandated treatments, which was vital.

Clear guidelines have been developed to deregulate Napa and Sonoma, and the state is considering removing the quarantine in Pope Valley and Chiles Valley with no mating disruption being used and increased trapping densities.

Quarantines have been lifted for Fresno, Merced, San Joaquin and Mendocino counties.

Clark summarized that the European grapevine moth is a very serious pest threatening the sustainability of winegrape and wine production in Napa County, other grape producing areas in the state and other grape growing regions of U.S.

“The battle is worth fighting and will take everyone’s commitment and cooperation; great progress has been made, and we need your help to continue this great work and eradicate EGVM from California so it will pose no threat to other grapegrowing areas of the country, and to help growers get out from under the burdensome and costly quarantine regulations.”

Currently no comments posted for this article.