Problem species in California include the western yellowjacket, Vespula pensylvanica, > V. atropilosa, V. sulfurea, V. vulgaris, and > V. germanica. Trapped wasps are dismembered in dry traps. Traps with collecting fluid were used to identify and quantify captured specimens. Preserving fluid used impacts catch, some alcohols being repellent. Propylene glycol was very effective. Trapping queens or foragers did not reduce resultant numbers but at one site trapping reduced the number of stings, perhaps by removing aggressive foragers.
Meat-based bait has the best potential for areawide control. Of 24 canned pet foods, foragers ignored 23. Trials of 0.05% chlorfenapyr and indoxacarb provided >90% control within 7 days. Rapid effects were obtained with dinotefuran. Results with bifenthrin, imidacloprid, spinosad, thiamethoxam, and others were less spectacular, perhaps because they were repellent at the rates tested.
Transfer was demonstrated whereby wasps lured with HB into fipronil-treated traps from which they were allowed to escape became donors. Fipronil was disseminated to recipient larvae via contact. Discovered nests were eliminated by occluding the entrance with a wire mesh cage soaked in 0.05% fipronil. Few foragers exited, but those received a sufficient dose to kill the colony.