Visual and olfactory disruption of orientation by the western pine beetle to attractant-baited traps

Olfactory deterrents have been proposed as tree protectants against attack by bark beetles, but their development has been hindered by a lack of knowledge of host selection behavior. Among the primary tree-killing (aggressive) Dendroctonus, vision appears to be an integral part of the host selection process. We evaluated the importance of vision in host finding by D. brevicomis LeConte, and our ability to affect it by modifying the visual stimulus provided by attractant-baited multiple-funnel traps. White-painted traps caught similar to 42% fewer D. brevicomis than black traps in California, USA (P < 0.05). Visual treatments were less effective (P < 0.0001) than olfactory disruptants (verbenone with ipsdienol), which reduced catch by about 78%. When combined, olfactory and visual disruptants resulted in similar to 89% fewer D. brevicomis being caught, but this combination was not more effective than olfactory disruptants alone (P > 0.05). Our results demonstrate that the visual component of D. brevicomis host finding behavior can be manipulated, but that D. brevicomis may be more affected by olfactory than visual disruptants. In contrast, visual disruption is more pronounced in the southern pine beetle, Dendroctonus frontalis Zimmermann, suggesting that non-insecticidal tree protection strategies for these related species should differ.