Evaluation of mass trapping and mating disruption for managing Prionus californicus (Coleoptera: Cerambycidae) in hop production yards.

Larvae of Prionus californicus Motschulsky (Coleoptera: Cerambycidae) feed on the roots of many types of woody perennial crops and are serious pests of hop in the northwestern United States. The adult males are strongly attracted to a volatile sex pheromone, (3R,5S)-3,5-dimethyldodecanoic acid, that is produced by females. Here, we summarize the results of field experiments that evaluated the potential for using the synthetic pheromone (in a blend of all four possible stereoisomers) to manage infestations of P. californicus in commercial hop yards by mass trapping or mating disruption. Our research provides evidence that mass trapping may be effective in reducing mating success of the females: positioning surrogate females (sentinel traps baited with a low dose of pheromone) within a square of eight pheromone-baited traps resulted in an 88% reduction in the number of wild males that reached the sentinel traps compared with sentinel traps that were surrounded by traps baited with blank lures. Similarly, surrogate females that were surrounded by pheromone lures (without traps) were reached by 84% fewer wild males than surrogate females surrounded by blank lures, suggesting that mating disruption also may be effective. A mark-recapture experiment indicated that male P. californicus were attracted to traps baited with 1 mg of pheromone from as far away as 585 m. These studies indicate that 3,5-dimethyldodecanoic acid has very good potential for managing P. californicus in hop yards, and perhaps in other crops where it is a pest.