Orientation of polyphagous lepidoptera to hostplant kairomones
Although in some oligophagous lepidopterans oviposition kairomones from hostplants can also serve as larval feeding stimulants, the relationships in chemistry of attraction of larval and adult stages to hostplants have rarely been examined in polyphagous species. Volatile constituents are known to serve as attractants for ovipositing moths. These compounds differentially stimulate electrophysiological responses in antennae of male and female moths and can also serve as larval attractants. Similarly, ovipositing female adults and feeding larvae use contact cues for hostplant evaluation. In this study, I reviewed the literature to determine if any patterns of relationship between adult and larval host recognition cues in polyphagous Lepidoptera have been detected in previous studies (Chapter 1). I then conducted a series of behavioral assays with the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), a highly polyphagous species, to determine if larvae of the navel orangeworm respond behaviorally to the same secondary compounds that elicit behavioral or electrophysiological responses in adult moths. In Petri dish arenas, navel orangeworm larvae showed a preference for 1-octen-3-ol and 2-phenylethanol, and aversion to ethyl benzoate out of a total of 9 tested compounds that are electrophysiologically active in male or female adults. The same behavioral assay was also used to investigate the role of volatiles emitted by a potentially mutualistic Aspergillus fungus in larval orientation behavior. Larvae were strongly attracted to methanolic extracts of almond meal spiked with fungal volatiles. In one case, larvae even preferred almond extract spiked with fungal volatiles over pure almond extract. This information may prove useful in refining current control systems for navel orangeworm; for example, my findings suggest that replacing lures when they become moldy may be counterproductive, and that adding volatiles to pesticide formulations may be effective in attracting larvae to areas that have been treated, thereby increasing the likelihood of encountering the pesticide.
kairomone, Lepidoptera, hostplant, navel orangeworm
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign