The effect of olfactory and visual cues on the host selection of the seed-feeding weevil, Mogulones borraginis

Current biological weed control testing procedures rely primarily on choice and no-choice feeding and developmental tests to assess the host range of potential agents.  Although investigating olfactory and visual cues can improve pre-release risk assessments in that an insect first locates a host plant based on the presence of olfactory and visual cues, there has been little focus on the role of these cues that underlie the host range of potential agents.  Using a portable volatile collection system and a double-stacked y-tube device, we found that female Mogulones borraginis, a seed-feeding weevil considered for the biological control of the rangeland weed houndstongue (Cynoglossum officinale), distinguished C. officinale from several native plant species when visual, olfactory, or combined cues were offered to weevils in dual-choice bioassays.  Here we also showed that the female weevils did not distinguish C. officinale from the native plant species in dual-choice bioassays when the two cues were reversed from C. officinale and other native plant species.  These results substantially advance our understanding of the pivotal role of olfactory and visual cues and may lead the way to new approaches for assessing the host range of prospective biological control agents.