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Second-generation EGVM trapped in Sonoma County

Moths representing the second generation of the European grapevine moth this season were trapped in early June in Sonoma County, Calif.

University of California Cooperative Extension Viticulture Farm Advisor Rhonda Smith and UC IPM Specialist Lucia Varela are recommending growers in a state quarantine for Lobesia botrana or within 0.6 miles of it consider making an insecticide application to control EGVM larvae.

The first moths of the second generation were trapped on June 10 in vineyards in Oakville and Rutherford. Grapes were severely damaged by EGVM last year in this same area. At least two vineyards were not harvested in 2009 because of the damage to fruit.

Three generations are expected this season on the North Coast.

More than 900 square miles have been placed under quarantine after moths were trapped last fall and this spring on the North Coast.

EGVM is unlike other tortricid vineyard pests found in California, according to the two UC scientists.

Its unique biology causes significant damage to clusters and reduces yields. Eggs are laid singly and almost exclusively inside grapevine clusters and larvae feed on and inside developing flowers and berries. In the second generation, females lay their eggs individually on berries. Initially the larvae will form a silken tunnel by the cluster rachis, tie several berries together and feed on berry surfaces. Larvae penetrate mid-size berries where two berries touch.

The preferred timing to achieve optimal control of EGVM during the second generation is during the egg or young larval stages. At this time of the year EGVM females will take about four to six days to mate and begin egg laying. Peak flight/peak egg laying is predicted for June 30. Egg and larval development is completed in about six and 25 days, respectively. Larvae then pupate and adult moths (third flight) emerge six to 14 days after pupae form.

At this time, Smith and Varela are encouraging conventional growers to apply Intrepid 2F (methoxyfenozide) or Altacor (chlorantraniliprole) for the second generation. Both are ovicidal and larvicidal and have activity against eggs and larvae. For the second generation Altacor is best timed pre-oviposition (any time between June 16 and June 24) and Intrepid is best timed against eggs, or against first and second instar larvae (any time between June 16 and June 30 preferably, but not later than July 7). At the higher rates, they will have about a 21-day residual.

For organic growers, the available materials are larvicidal only and do not have as long residual.

These include Entrust (spinosad) and “Bt” (Bacillus thuringeinsis) products. The first application of either of these materials should be made at egg hatch which is estimated to be about June 24, according to the two UC experts.

Two or more weekly applications are required to control larvae.

Spray coverage is critical; aim at the clusters and use enough water to thoroughly wet. Although it is not expected, Smith and Varela indicate it is possible that EGVM larvae will be missed by a single application of a conventional material for a few reasons. First, the application may have gone on late and larger worms are difficult to kill; second, spray coverage on clusters was poor. If larvae are found in clusters two to three weeks after an application, and they are confirmed to be EGVM, growers will have to make a second application with a different material. The following products are options: Success, Avaunt, Delegate and Agri-Mek. It is assumed that growers who use a Bt or Entrust will have to make at least three applications in the second generation.

Pyrethroids, carbamates and organophosphates also control EGVM, but they are highly disruptive to natural enemies, according to Smith and Varela. Specifically, natural enemies of grape mealybug and spider mites will be killed and damage will be caused by these pests.

Lobesia botrana was verified in Napa County in September 2009. It was the first find of this Lepidopteran pest in North America.

EGVM is currently targeted for eradication in California by the California Department of Food and Agriculture (CDFA) and the United States Department of Agriculture – Animal Plant Health Inspection Service (USDA-APHIS).

Pheromone traps that attract male adult moths are deployed and monitored by the Sonoma County Agricultural Commissioner at a density of 16 traps per vineyard square mile. If two or more adult male moths are caught in traps placed no further than three miles apart, then a quarantine is established by CDFA. A quarantine is also triggered if more than one adult moth is caught in a single trap. The quarantine encompasses a five-mile radius from the trap(s) that caught moths. Trapping density increases to 25 traps per vineyard square mile inside a quarantine area. Traps are serviced every two weeks.

Sonoma County growers may place their own pheromone traps for EGVM. However, growers are asked not to place traps within 30 meters of any other EGVM trap in a vineyard.

TAGS: Management
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