Developing mating disruption for the integrated management of grape berry moth

Project Code PRR07-230

Project Lead

Robert Trimble - Agriculture and Agri-Food Canada

Objective

To determine whether reduced application rates of pheromone dispensers through peripheral treatments can be used to achieve effective and economic control of grape berry moth (GBM). Conduct a cost/benefit analysis of this reduced rate technology.

Summary of Results

Background

The grape berry moth, Paralobesia viteana (Clemens) is the most important insect pest of grapes in eastern North America with two-three generations appearing per year in Canada. Its management relies largely on the use of pesticides. In Niagara peninsula vineyards, one or two applications of organophosphate insecticide have been typically used to control this pest. However, registrations of these insecticides have been cancelled, or their use has been made more difficult because of the U.S.A. Food Quality Protection Act and a pest control product re-evaluation program in Canada. The efficacy of lower risk insecticides that could be used in place of organophosphate insecticides has been examined in the U.S.A. and in Canada. There was, however, a need for increased research and development effort on alternative approaches to minimize the use of insecticides for controlling P. viteana.

The use of synthetic sex pheromone to disrupt sexual orientation, otherwise known as "mating disruption", is an alternative control method that may lead to the transition from insecticides-based management to integrated pest management (IPM). Mating disruption has been successfully used to control P. viteana in Ontario vineyards, but there has been limited adoption of this technique by growers. The primary reason for the low adoption rate is the higher cost of using pheromone compared to insecticides. Isomate GBM® Plus pheromone dispensers is the only commercial mating disruption product currently available to Canadian grape growers. One method of reducing the cost of mating disruption technique would be the use of reduced rates of pheromone dispensers.

Approaches

The effect of peripheral treatments with pheromone dispensers in controlling P. viteana was investigated in three commercial vineyards in the Niagara peninsula, Ontario in 2007. Four 1 hectare plots were established within each of the three vineyards. The activity and mate-locating ability of male P. viteana was monitored in each plot using 25 synthetic sex pheromone-baited delta traps (Cooper Mill Ltd., Madoc, Ontario) that were positioned 1 m above the ground on a 20 m x 20 m grid prior to first moth flight in the spring. Each trap was baited with a 9 mm-diameter, natural-rubber sleeve stopper (Chromatographic Specialties, Brockville, Ontario) loaded with 0.8 mg of Z-9-dodecenyl acetate (Z9-12:OAc) and 0.2 mg of (Z)-11-tetradecenyl acetate (Z11-14:OAc) (Pherobank, Plant Research International, Wageningen, the Netherlands). Moths were counted and removed from the traps on Mondays and Thursdays from May 22 until September 10 in 2007. Stoppers were changed at the end of the 1st and 2nd of the three flights of P. viteana.

The Isomate® GBM Plus pheromone dispensers, each containing 221.5 mg of Z9-12:OAc (Pacific Biocontrol Corp., Vancouver, WA) were deployed after peak trap catch during the second flight (between July 6 and 11) of P. viteana moths. Each of the four plots in each vineyard received one of the following four treatments: 1) pheromone dispensers applied at equal spacing to the entire plot at the recommended rate of 500 units/hectare; 2) dispensers applied to the periphery of the plot at intervals of 5 m; 3) dispensers applied to the periphery of the plot at intervals of 2.5 m; and 4) no treatment with pheromone dispensers (i.e. untreated control). Dispensers were attached to the top trellis wire 110-120 cm above the ground within the grape vine canopy. Moth counts trapped in each plot before and after pheromone dispensers were applied and feeding injury to grape clusters by P. viteana larvae were assessed.

Results

The application of Isomate® GBM Plus dispensers at a rate of 500 units/hectare reduced the mean total number of moths trapped by 96% compared to the untreated control, indicating a high level of mating disruption. Trap catch was reduced by 87% when dispensers were applied at intervals of 2.5 or 5 m along the periphery of 1 hectare plots of vines, but the reduction was not significantly different from the untreated control. The economic injury threshold of 2% infested grape clusters was not exceeded in any of the inspected plots. Results of this study demonstrate some potential for using peripheral treatments with pheromone dispensers for controlling P. viteana by mating disruption. Additional experiments using greater replication should be undertaken to confirm the current results and increase the likelihood of detecting significant treatment effects when using peripheral treatments. It is recommended that any future experiments should also include the use of tethered, virgin-female moths to confirm that the pheromone treatments are affecting the ability of male P. viteana to locate and mate with sexually receptive females. The successful outcomes from peripheral treatments with pheromone dispensers would make the use of pheromone for P. viteana management considerably less expensive for grape growers. For example, in a 200 m-wide by 500 m-long, 10 hectare vineyard, enclosing each of the 1 hectare "plots" in the vineyard with dispensers spaced at 2.5 or 5 m intervals would result in a 78 and 89% reduction in the number of dispensers required, respectively, compared to the minimum recommended application rate of 500 dispensers/hectare.

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