Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2008
Publication Date: 6/26/2008
Citation: Williams III, L.H., Rodriguez-Saona, C., Castle, S.C., Zhu, S. 2008. Herbivore-Induced Plant Volatiles Influence Neurophysiological And Behavioral Responses Of And Host Attack By An Egg Parasitoid. Journal of Chemical Ecology. 34:1190-1201
Interpretive Summary: Plant bugs are serious pests of many crops, including cotton and soybean, in the United States. Beneficial insects are useful in killing plant bugs, and may use odors from damaged plants as ‘distress signals’ to find the plant bugs. Thus, understanding the interactions between plant bugs, plant distress signals, and attraction of beneficial insects has important implications for plant bug control. We conducted experiments to evaluate the perception of plant odors by a beneficial insect, and the degree of attraction the insect exhibits to the odors. An additional study was conducted in a cotton field to determine the effect of odors on attack of plant bug eggs by the beneficial insect. Our results indicate that the beneficial insect smelled some plant odors better than others, and that females usually had more acute odor perception than males. Females were also attracted by several of the odors, and this attraction could be heightened by training the insects with odors prior to the experiment. In the field experiment plant bug eggs treated with plant odors suffered higher attack by the beneficial insect than did eggs without plant odors. Our findings indicate that attraction to plant distress signals can be increased by learning, and suggest that the behavior of beneficial insects can be manipulated based on this training. Individual plant odors, many of which are commercially-produced, can be used to increase attack rates on plant bug eggs.
Technical Abstract: Volatiles emitted by plants in response to Lygus species feeding were tested in neurophysiological, behavioral, and parasitism trials with Anaphes iole, an egg parasitoid of Lygus. Electroantennogram (EAG) analyses indicated that A. iole antennae responded to most herbivore-induced plant volatiles (HIPVs) included in the test, and that females were usually more responsive than males. Antennal responses to (Z)-3-hexenyl acetate and methyl salicylate were among the strongest. Behavioral assays in a four-arm olfactometer demonstrated that attraction of female wasps to (Z)-3-hexenyl acetate varied greatly depending on preconditioning regime. Preconditioning stimuli to complex host-plant odors led to stronger attraction than did a single preconditioning stimulus, i.e. (Z)-3-hexenyl acetate. In a horizontal wind tunnel, we demonstrated that methyl salicylate and a-farnesene were attractive to female wasps. Parasitism of Lygus lineolaris eggs by A. iole in a cotton field was greater when the eggs were associated with (Z)-3-hexenyl acetate or a-farnesene than with controls. Overall, the results of this study showed that A. iole can perceive a variety of plant volatiles released after its host damages plants, that the degree of associative learning in A. iole can be manipulated based on preconditioning regime, and that single synthetic HIPVs are attractive to A. iole and can be used to increase attack rates on host eggs. Therefore, it appears that HIPVs have potential for use in suppression of Lygus species.