Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/1998
Publication Date: N/A
Citation: N/A Interpretive Summary: Herbivorous insects use chemical and physical cues to locate suitable host plants. Specialist and generalist predators used as biocontrol agents for CPB must use cues to locate their herbivorous prey. Until now, little was known about chemicals used by CPB to locate its host plant or those used by its generalist and specialist predators. I have now discovered that CPB is sensitive to specific chemicals released by undamaged or artificially-damaged plants and those damaged by insect feeding. Both generalist and specialist predators were sensitive to chemicals emitted by insect-damaged plants. The specialist predator was more sensitive to these compounds than was the generalist. A blend of constitutive chemicals released at the wound site during CPB feeding and systemic chemicals released by the whole plant following periods of feeding attracted both CPB and its generalist predator. The discovery of chemicals detected by CPB and its predators will be used by entomologists to develop an attractant for field use, and chemical ecologists and evolutionary biologists to explain complex interactions among plants and insects.
Technical Abstract: Olfactory responses of the Colorado potato beetle (CPB) generalist predator, Podisus maculiventris (Say)(Pm) and a specialist predator, Perillus bioculatus (F.)(Pb) were investigated. Volatiles tested included 20 compounds emitted by undamaged potato plants, plants that had been artificially damaged, or plants damaged by feeding by CPB larvae. Coupled gas chromatograph/electroantennogram recordings revealed six compounds for which reliable responses were recorded from CPB antennae: (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (+/-)-linalool, nonanal, (Z)-3-hexenyl butyrate, methyl salicylate, and indole. Both Pm and Pb responded selectively to the same compounds as the CPB with the exception of (E)-2-hexen-1-ol and (Z)-3-hexen-1-ol. Dose response curves showed that CPB was at least 100 x more sensitive to (E)-2-hexen-1-ol than were the predators. Both predators were more sensitive to each of the other compounds than were CPB. These results show that the herbivore (CPB) has olfactory receptors which are more sensitive to constitutive host plant volatiles, e.g. green leaf volatiles, while both generalist (Pm) and specialist (Pb) predators are more sensitive to systemic volatiles produced in response to prey feeding.