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

Mass-trapping using semiochemical lures is a potentially useful control measure against bark beetle pests. A serious problem, however, is the inadvertent removal of predators that respond to these baits as kairomones. Ips pini (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. Its response is increased by a synergist, lanierone. Its most abundant predators in Wisconsin include Thanasimus dubius (F.), which responds to similar blends of ipsdienol, and Platysoma cylindrica (PaykuII) and P. parallelum (Say), which respond to primarily (-) enantiomers of ipsdienol. These predators do not show increased response when lanierone is released in addition to ipsdienol. We conducted a no-choice assay using rotating blends of ipsdienol and lanierone to simulate a trap-out treatment. Lures that contain enantiomers of ipsdienol most preferred by I. pini, in combination with lanierone, can selectively remove up to three to six times more pests than predators during the spring. Moreover, delaying deployment of the same lures until summer can result in removal of up to 39 times 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 beetle trapped. Exploiting these behavioral differences between pests and predators can improve biological control by conserving predators during trap-out programs.