2009 Annual Report

Gray rubber septum lure for mealybugs in a sticky trap surrounded by captured male mealybugs.
Photo by Steve McElfresh.

Combination lure for mealybugs cuts costs

UC researchers have found the same generic lure can attract three species of mealybugs, which would cut costs for growers by allowing them to use a single pheromone trap.

Without careful, regular sampling, mealybugs can reach economically damaging levels before growers realize infestation has occurred. However, the only scouting tool nurseries currently use for citrus, longtailed, and obscure mealybugs is a labor-intensive, visual inspection of crops. With the synthetic pheromone lures, which are deployed in sticky traps, it is easier to capture and count the males.

Researchers also are assessing the reproductive biology of the three species to determine if pheromone-based control measures such as mating disruption are likely to be successful.

During the past two years, 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 the three 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.

When developing the lures, researchers had to take into account the dose and longevity of the pheromone as well as how to monitor the seasonality of field populations.

Waterworth’s results show longtailed mealybugs have clear, 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.”

While studying mating disruption, researchers 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 using pheromones to monitor or control 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, he added.

The UC IPM Competitive Grants Program funded this study.

Contact

Jocelyn Millar, (951) 827-5821

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