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The same generic lure can attract three species of mealybugs, which would cut costs for growers by allowing them to deploy a single pheromone trap rather than three. The only scouting tool nurseries currently use for mealybugs is labor-intensive visual inspection of crops. Mealybugs are cryptic pests that conceal themselves in cracks and crevices of plant material. Without careful and regular sampling, mealybugs can reach economically damaging levels before growers realize plant-material infestation has occurred. During the past two years, University of California, Riverside, researchers, including graduate student Rebeccah Waterworth, who is studying with UC Riverside entomologist Jocelyn Millar, has worked in several nurseries in Riverside and San Diego counties, deploying pheromone-baited traps to detect and follow citrus, longtailed and obscure mealybug populations.

"Fortunately our experiments determined that there is no major interference among these pheromones so a combination lure containing the pheromones of all three mealybug species can be used," Waterworth said.

The synthetic pheromone lures are deployed in sticky traps, where male mealybugs are then captured and counted. Some of the practical questions involved in developing pheromones for trapping mealybugs include the dose and longevity of the pheromone lures and how to monitor the seasonality of field populations of the three species.

Waterworth's results show longtailed mealybugs have clearly seasonal trends in their activity with populations increasing October through early spring and falling to low levels during the hotter summer months.

"The major peak in activity during the cooler winter months was counterintuitive, because most other insect pests show declines in their activity through fall and winter," Millar said. "The seasonality of this species is also apparent in other crops at this production location."

In addition, researchers are assessing the reproductive biology of the three mealybug species to determine whether pheromone-based control measures, such as mating disruption, are likely to be successful. They examined whether females can reproduce asexually as well as sexually, the number of times both males and females can mate, and details of their reproductive behaviors that might have implications for the use of pheromones for monitoring or controlling these insects.

"With citrus mealybug, we found that males and females can mate multiple times, as long as matings occur rapidly," Millar said. "However, one day after mating the first time, females become unreceptive to further mating attempts, suggesting that materials transferred to the female during mating have triggered changes in the female's physiology. Similar studies are in progress with the other two mealybug species."

The UC Integrated Pest Management Competitive Grants Program funded this study.