Vine mealybugs or their honeydew found in grape clusters at harvest result in grapes that are not fit for consumption and do not meet the strict quality standards required for export. That is why vine mealybug is the most significant pest of table grapes in California. Adding to the complexity of managing this pest, the steps to successful management depend on location (vine mealybug can have two to three generation in coastal areas versus five to seven in the Central Valley); harvest dates, which vary widely depending on the cultivar; other pests present in the vineyard; and natural enemies present. Decisions for how to manage vine mealybug need to be made for each vineyard.
Mating disruption, flooding the vineyard with the pheromone females emit to attract males, has recently become available. Males can’t find females when there is pheromone everywhere in the vineyard, so the mealybugs don’t reproduce. University of California Cooperative Extension Advisor and UC IPM Affiliated Advisor David Haviland evaluated the use of microencapsulated pheromone as part of an IPM program for vine mealybug in table grapes. The microencapsulated pheromone is carried in a liquid that can be applied using a standard sprayer. Once applied, the pheromone is slowly released into the vineyard.
Haviland evaluated two application timings of the pheromone, a 30-day interval and a 45-day interval over the season. All experimental vineyards, with or without mating disruption, received standard insecticide applications. Mating disruption was evaluated by assessing the number of male mealybugs found in traps and looking for vine mealybugs in grape clusters at harvest.
Haviland found that pheromone applications at 30-day intervals continuously reduced the capture of male mealybugs in traps compared to the number of male mealybugs found in traps in the experimental vineyards without mating disruption. In the 45-day interval timing experimental vineyards, fewer male mealybugs were caught in traps for 30 days, but after 30 days, Haviland observed a resurgence of male mealybug numbers. In experimental vineyards where pheromone was applied every 45 days, the number of male mealybugs captured in traps was approximately 4 to 7 times higher than the number of mealybugs captured in vineyards where the pheromone was applied every 30 days.
Harvested grape clusters in the 30-day interval mating disruption vineyards had fewer mealybugs compared to the experimental vineyards where no pheromone was applied. Similar numbers of mealybugs were found in the grape clusters in vineyards where the pheromone was applied at 45-day intervals and no pheromone was applied.
Based on the reduction of infested grape clusters by mating disruption, Haviland calculated a savings of approximately $32 and $136 per acre for two experimental vineyards. The cost of pheromone application is approximately $60 per acre. He also points out a savings on the costs of labor by reducing the number of infested clusters. Infested grape clusters slow picking, processing, and packing clusters.
Haviland concludes that adding mating disruption enhances the management of vine mealybug and that more research is needed. His research is improving the integrated pest management program for vine mealybugs. Other potential outcomes: reduced insecticide applications, reduced numbers of mealybugs without increased insecticide use, improved crop quality, improved sustainability of grape production, and improved profitability of grape production.