Effect of semiochemical exposure on flight propensity and flight capacity of Dendroctonus ponderosae in laboratory bioassays

Abstract

During flight,\xa0insect herbivores respond to volatile organic compounds (VOCs) released by host and non-host plants or conspecifics. Dendroctonus ponderosae uses chemical cues including host and non-host VOCs, as well as aggregation pheromones to navigate through the environment and find a suitable reproductive host. The dispersal flight distance of D. ponderosae from its natal host to its reproductive host varies widely, even within populations of beetles. Beetle energetics do not entirely explain this flight variation. In this study, we test the effect of beetle exposure to semiochemical cues before and during flight on subsequent flight propensity (the likelihood of flight initiation) and flight capacity (the distance and velocity of flight) using computer-linked flight mills. Exposure to host volatiles before flight interacts with beetle pre-flight weight to influence subsequent flight capacity of female but not male beetles. Female beetles flew further and faster following exposure to their aggregation pheromone, trans-verbenol. Flight of female beetles was reduced when they were exposed to volatiles from the non-host, Populus tremuloides, during flight. This study is the first to indicate that semiochemical cues not only influence beetle orientation during flight but also flight capacity of D. ponderosae. These results provide baseline information on the effect of environmental cues on dispersal by flight of D. ponderosae.