Visual and semiochemical disruption of host finding in pine bark beetles.

摘要

Pine bark beetles (Coleoptera: Scolytidae) affect ecological and anthropocentric processes in coniferous forests. Certain aggressive species, particularly among the Dendroctonus, cause widespread damage. As forests become increasingly valued for diverse commodities, protection strategies must be developed to meet a wide variety of landowner values. Disruption of the host selection process is one important strategy for managing pine bark beetles. The objectives of this work were: to describe the oleoresin flow and constituency of loblolly pines (Pinus taeda) whose parents escaped mass attack by the southern pine beetle, Dendroctonus frontalis (SPB); to ascertain the utility of altering visual silhouettes to disrupt host finding by the SPB; and to evaluate these effects on other scolytids, in particular the western pine beetle, Dendroctonus brevicomis (WPB). Pine defenses, particularly oleoresins, may disrupt bark beetle host selection and prevent colonization. Oleoresin characteristics of first-generation progeny of loblolly pines that escaped SPB-caused mortality were compared to trees from a general (unselected) population. Concentrations of 11 oleoresin constituents did not differ between the two populations. However, escape trees yielded 65% more oleoresin, supporting the hypothesis that increased flow may improve tree survival. The use of silhouette modification for disrupting host finding, with and without olfactory deterrents, was evaluated in SPB and WPB. White colored multiple-funnel traps and painted trees in the field caught 70--80% fewer SPB, and reduced catch of a common predator, Thanasimus dubius, by 56--85%. Visual (white color) and olfactory deterrents combined caused a reduced catch of SPB in traps by ∼90%. With WPB, white colored multiple-funnel traps reduced catch by 42% compared to black, while olfactory deterrents reduced catch by 78% compared to traps with attractants alone. Together, olfactory and visual deterrents reduced catch of WPB by 88%. White traps alone caught fewer Temnochila chlorodia , a common predator of WPB, than black traps. These results, overall, show that host selection by Dendroctonus species and their predators may be significantly affected by visual silhouettes, and that, when combined with olfactory deterrents and/or oleoresin flow, may be used in effective non-lethal disruption strategies.