Whether plants respond to cues produced by neighbors has been a topic of much debate. Recent evidence suggests that wild tobacco plants transplanted near experimentally clipped sagebrush neighbors suffer less leaf herbivory than tobacco controls with unclipped neighbors. Here we expand these results by showing evidence for induced resistance in naturally rooted tobacco when sagebrush neighbors are clipped either with scissors or damaged with actual herbivores. Tobacco plants with sagebrush neighbors clipped in both ways had enhanced activity levels of polyphenol oxidase (PPO), a chemical marker of induced resistance in many solanaceous plants. Eavesdropping was found for plants that were naturally rooted, although only when sagebrush and tobacco grew within 10 cm of each other. Although tobacco with clipped neighbors experienced reduced herbivory, tobacco that grew close to sagebrush had lower production of capsules than plants that grew far from sagebrush. When neighboring tobacco rather than sagebrush was clipped, neither levels of PPO nor levels of leaf damage to tobacco were affected. Eavesdropping on neighboring sagebrush, but not neighboring tobacco, may result from plants using a jasmonate signaling system. These results indicate that plants eavesdrop in nature and that this behavior can increase resistance to herbivory although it does not necessarily increase plant fitness.

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Rhopalosiphum padi L. (Homoptera: Aphididae) is sensitive to loline alkaloids present in tall fescue, Festuca arundinacea Shreb., infected with the endophytic fungus, Acremonium coenophialum Morgan‐Jones & Gams. Aphid survival was higher on endophyte‐free plants regardless of plant age after germination or age of regrowth tissue after clipping. Survival of aphids on endophyte‐infected grass was lower on young tissue but increased as plants aged, although it never reached the same level on endophyte‐free plants. Both N‐formyl and N‐acetyl loline increased as uncut or regrowth tissue aged; however, this was influenced by the age of the plant at the initial cut and the clipping frequency. Although even small amounts of loline cause high aphid mortality, the aphids are able to survive on endophyte‐infected plants if the tillers have senescing leaves which contain lower amounts of loline. Preference for senescing leaves may help R. padi avoid plant parts containing high amounts of toxic allelochemicals, thus contributing to higher numbers of aphids on older, endophyte‐infected plants.

A group of sensilla present on the maxillary galea of adult western corn rootworm,Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) beetles has been identified morphologically and physiologically to be involved in taste mediation. There are approximately 15 chemosensory hairs on each galea. Bilateral removal of these structures resulted in a significantly reduced consumption of a strongly phagostimulant triterpenoid, cucurbitacin B, and led to increased ingestion of a phagodeterrent alkaloid, strychnine. Electrophysiological responses obtained via tip-recording of galeal chemosensilla with submillimolar concentrations of host and nonhost plant compounds resulted in dose responses overlapping with the effective behavioral ranges. Cucurbitacin B was found to evoke chemosensory responses at levels as low as 0.1µM. Sinceγ-aminobutyric acid (GABA) is an agonist. (-)-β-hydrastine and strychnine are antagonists, and cucurbitacin B has been proposed to act at a separate modulatory site of classical synaptic GABA and glycine receptor-channel complexes, results reported here raise the possibility that there are peripheral chemosensory receptor sites that may resemble, functionally and structurally, synaptic receptor sites in the central nervous system.

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