Professor of Entomology University of California Riverside, California
Yellowjackets are an important seasonal pest of recreational and outdoor areas in the western United States. The western yellowjacket, Vespula pensylvanica, and Vespula alascensis are especially problematic because of the predilection to forage on human foods. Traps have been popular in attempting to control foraging yellowjackets. Several different commercial traps and some improvised trap designs with heptyl butyrate are effective in trapping large numbers, but they typically fail to provide control. Traps are an essential tool in monitoring yellowjackets. The challenges facing the use of baits to control yellowjackets are determining effective active ingredients, finding attractive and palatable bait bases, and extending the longevity of baits when applied in the field. Fipronil (0.025%) combined with minced canned chicken breast is an effective bait. Two isoxazolines, fluralaner and sarolaner, also show promise as active ingredients in bait. Minced canned chicken breast and the juices extracted from the canned meat are highly attractive and palatable. To extend the longevity of the bait in the field, chicken juices are mixed with polyacrylamide gels (PAA) and toxicants provide a bait that is attractive for 72 hours. Molecular studies utilizing satellite markers indicate that numerous yellowjacket colonies visit each monitoring station. A minimum of 20 colonies were detected at one site alone. Baiting with 0.025% fluralaner in PAA crystals reduced the number of colonies detected to 6 after 30 days. More extensive baiting programs will be necessary to deal with the numerous yellowjacket colonies attracted to individual monitoring and bait stations.
