Exploiting behavioral disparities among predators and prey to selectively remove pests: Maximizing the ratio of bark beetles to predators removed during semiochemically based trap-out

Mass-trapping using semiochemical lures is a potentially useful control mea sure against bark beetle pests. A serious problem, however, is the inadvert ent removal of predators that respond to these baits as kairomones. Ips pin i (Say) infests hard pines in the western, Great Lakes, and eastern forests of North America. In Wisconsin, I. pini responds primarily to 50(+) /50(-) and 75(+) /25(-) blends of ipsdienol, its principal pheromone component. I ts response is increased by a synergist, lanierone. Its most abundant preda tors in Wisconsin include Thanasimus dubius (F.), which responds to similar blends of ipsdienol, and Platysoma cylindrica (Paykull) and P. parallelum (Say), which respond to primarily (-) enantiomers of ipsdienol. These preda tors do not show increased response when lanierone is released in addition to ipsdienol. We conducted a no-choice assay using rotating blends of ipsdi enol and lanierone to simulate a trap-out treatment. Lures that contain ena ntiomers of ipsdienol most preferred by I. pini, in combination with lanier one, can selectively remove up to three to six times more pests than predat ors during the spring. Moreover, delaying deployment of the same lures unti l summer can result in removal of up to 39 rimes more pests than predators. In contrast, lures that contain enantiomers of ipsdienol most preferred by predators can inadvertently remove two or more predators per each bark bee tle trapped. Exploiting these behavioral differences between pests and pred ators can improve biological control by conserving predators during trap-ou t programs.