EAG-Active Herbivore-Induced Plant Volatiles Modify Behavioral Responses and Host Attack by An Egg Parasitoid

Abstract

Volatiles emitted by plants in response to feeding by Lygus species were tested in neurophysiological, behavioral, and parasitism trials with Anaphes iole, an egg parasitoid of Lygus. Electroantennogram analyses indicated that A. iole antennae responded to most herbivore-induced plant volatiles (HIPVs) tested 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 response of female wasps to (Z)-3-hexenyl acetate varied greatly depending on preconditioning regime. Preconditioning wasps to complex host-plant odors led to stronger preference than did a single preconditioning stimulus, i.e., (Z)-3-hexenyl acetate. In a horizontal wind tunnel, female wasps were attracted by methyl salicylate and α-farnesene. 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 α-farnesene than with controls. Overall, the results of this study show 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 population densities.

Chemical Ecology of Egg Parasitoids Associated with True Bugs

“…Induced plant volatiles are also exploited by mymarids [43,44] (Table 1). Feeding on cotton, and several other plants, by either sex of Lygus hesperus Knight (Miridae) results in the induction of volatiles that are behaviorally and physiologically active towards Anaphes iole Girault (Mymaridae).…”

“…Therefore, egg parasitoids have developed specialized strategies to overcome the reliability-detectability dilemma in order to efficiently parasitize host eggs. Successful parasitism is accomplished hexenyl acetate, methyl salicylate Attraction in olfactometer (effect of experience); response to EAG [43,44,67] Short range synomones…”

Manipulation of Natural Enemies in Agroecosystems: Habitat and Semiochemicals for Sustainable Insect Pest Control

“…Ample evidence exists in the literature from laboratory studies that natural enemies can respond to HIPVs (Mumm & Dicke, 2010). For example, Anaphes iole Girault, an egg parasitoid of Lygus spp., showed a strong antennal response (based on electroantennogram -EAG-analysis) to (Z)-3-hexenyl acetate and MeSA (Williams et al, 2008). Gas chromatographic-electroantennographic detection (GC-EAD) analysis showed that MeSA elicits a significant antennal response in C. septempunctata (Zhu & Park, 2005).…”

“…For example, four HIPVs: linalool, (E)--ocimene, (3E)-4,8-dimethyl-1,3,7-nonatriene, and MeSA attracted females of the predatory mite P. persimilis in Y-tube olfactometer assays (Dicke et al, 1990b;De Boer & Dicke, 2004a). In a wind tunnel, Williams et al (2008) showed attraction of A. iole females to MeSA and -farnesene. Thus, it is safe to infer that natural enemies are also being directly attracted to the synthetic lure in the field.…”

“…More recently, Williams et al (2008) reported greater parasitism of Lygus lineolaris (Palisot de Beauvois) eggs by A. iole in cotton fields when dispensers containing (Z)-3-hexenyl acetate and -farnesene were placed near the host eggs. In field cage studies in cotton, Yu et al (2010) found higher parasitism of Helicoverpa armigera (Hübner) larvae by Microplitis mediator Haliday in cages treated with 3-7-dimethyl-1,3,6-octatriene.…”