Traps and Protein Bait To Suppress Populations of Yellowjackets (Hymenoptera: Vespidae)
  Key Words  
  Vespula, wasp, baiting, trapping, attractant, lure
  Donald a. Reierson, Michael K. Rust, and Richard S. Vetter
  Seasonal and annual intensity of foraging pestiferous yellowjackets in California (USA) was determined with wet capture traps using heptyl butyrate (HB) lure. Although 3 species were sympatric at every test site, the most abundant at > 85 to 90% of total was V. pensylvanica (Saussure). There was a nearly 40-fold annual variation in the total number captured at some sites, the ultimate number of foragers apparently related to spring weather episodes. Independent of total number caught, traps indicated typical summer-fall seasonality, with the peak occurring in the warmest months. Queens and workers were attracted to HB. Early-season queen trapping and season-long trapping of foragers did not reduce the number of daily foragers nor reduce the number of reported sting episodes. In the short-term a ring of strategically placed interceptive traps reduced the number of yellowjackets foraging at a picnic food pavilion. Longer-term control was achieved one year with proprietary baits. Longer-term control one year was achieved with bait. Using minced chicken or one specific commercial fish-flavored pet food as the matrix, 0.05% chlorfenapyr or indoxacarb provided >90% non-resurgent control within 7 days. Results with bifenthrin, imidacloprid, and others were less spectacular, probably because of being repellent or having too rapid KD effects. Confirmation trials indicated that bait efficacy depends upon a minimum number of foragers/day. Trap catch is a good indicator of that minimum, there generally needing to be about 25 wasps/trap/day for baiting to be effective. Control may be achieved with toxicants such as fipronil or indoxacarb as they are transferred from the cuticle of foragers to other wasps in the colony. This transfer was substantiated by placing a wire-mesh cage soaked with 0.05% fipronil over a nest entrance for 15 min. The few caged exiting wasps were released and allowed to return to the colony, whereupon the colony was eliminated within 1 day.