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European grapevine moth getting around

To be such a poor flyer, the European grapevine moth (EGVM) is sure getting around.

The latest California grape pest has been trapped in six counties this season covering a wide area, and the season is still young.

It is 200 miles from Napa where the first EGVM was trapped this year to Fresno County where several were trapped recently.

The EGVM finds have prompted University of California farm advisors and specialists, local ag officials and state officials to organize a series of informational meetings in the central San Joaquin Valley.

The first is tomorrow from 10 a.m. until noon at the University of California Kearney Ag Center in Parlier.

University of California IPM specialist Walt Bentley and program organizer, Steve Vasquez, Fresno County UCCE farm advisor, are expecting a big crowd.

Although it posed a major threat to grapes through its three-generations a season, it is relatively easy to control with existing products. It also is far less ominous than the vine mealybug, which has spread rapidly through grape growing areas.

What makes EGVM particularly onerous are the quarantines that are imposed when more than two moths are trapped in the same area.

“The vine mealybug is far more damaging, but it is the marketing disruption the European grapevine moth quarantine represents that has many growers concerned,” said Bentley.

The California finds are the first for the U.S. and could pose serious marketing disruptions in both the domestic and international markets.

The weak-flying EGVM is getting around by hitchhiking through the state. Some believe the finds in Fresno County this spring are overwintering moths brought into the Valley last fall in lugs of grapes from Napa by home winemakers.

They could also have traveled the 200 miles from Napa to Fresno on equipment, specifically mechanical grape harvesters and gondolas. Custom harvesters cover the state gathering the crop from Bakersfield to Clear Lake.

Bentley has seen EGVM infestations in Chile where growers and researchers there are open about the problem because it seems to be easy to control.

“Most growers are relying on Intrepid or Delegate to control it. DiPel is also effective,” he said.

DiPel is approved for organic production. It takes several applications of the slow acting Bt product to control the pest. Apparently growers are also mixing DiPel in with powdery mildew disease control sprays.

Worldwide there are different strains of EGVM. The one found in Greece feeds on peaches and other fruit besides grape. The one in California is believed to be the strain from Spain and it only damages grapes.

While the current EGVM SJV finds are likely overwintering visitors, the first generation of the pest is expected to appear in late June or early July. Bentley does not believe there is a breeding population in the Valley despite the multiple finds. However, no one can be sure of that until the first-generation time frame has passed.

There is a mating disruption pheromone available, but regulators are not encouraging it since putting out the pheromone will mask any attempts to trap the pest and identify the area where it can be found.

Masking traps would help establish a permanent population of this pest.

When it’s found, growers go after it in a hurry with pesticide applications to head off any damage and spread of the pest that is spawning large quarantined areas.

If not controlled, Lobesia botrana can devastate an entire vineyard.

Depending on climate, EGVM may have as many as four generations a year. The first-generation larvae feed on the vine’s flowers, which may fail to develop, or grape bud clusters. Larvae of the second generation attack green berries, hollowing them out and leaving just the skins and seeds. The third generation inflicts the greatest damage, feeding on ripening grapes and leaving them open to fungal infections of grey mold (Botrytis) and ruination.

Growers are wasting no time in taking aggressive action to prevent EGVM from gaining a foothold in California. At ground zero, Napa County, Napa Valley Grape Growers and Napa Valley Vintners have been leading the charge. Growers in quarantined areas sprayed conventionally-grown vineyards with a pesticide. Organic growers are using Bt products.

Growers in quarantined areas are also cleaning equipment with high pressure water or air blasts before moving to other vineyards.

After multiple finds in Fresno County, the county’s Department of Agriculture and Information Technology Services Department have set up voice mail messaging system to keep growers informed on the latest information on EGVM. The number is (559) 600-EGVM.

Growers can call anytime. If growers have additional questions, they can leave a contact phone number and a time convenient for a return call.

Besides the meeting tomorrow, two more sessions are scheduled for May 22 at the California Tree Fruit Agreement, 975 I Street, Reedley, Calif., (10 a.m.-noon) and May 27 from 6 p.m-8 p.m. at the Fresno County Farm Bureau, 1274 W. Hedges, Fresno, Calif.

A second, afternoon EGVM information meeting has scheduled for tomorrow afternoon at Kearney Ag Center. It is planned for 1-3 p.m. Wednesday.


TAGS: Management
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