A Challenge for a Male Noctuid Moth? Discerning the Female Sex Pheromone against the Background of Plant Volatiles

Abstract

Finding a partner is an essential task for members of all species. Like many insects, females of the noctuid moth Heliothis virescens release chemical cues consisting of a species-specific pheromone blend to attract conspecific males. While tracking these blends, male moths are also continuously confronted with a wide range of other odor molecules, many of which are plant volatiles. Therefore, we analyzed how background plant odors influence the degree of male moth attraction to pheromones. In order to mimic a natural situation, we tracked pheromone-guided behavior when males were presented with the headspaces of each of two host plants in addition to the female pheromone blend. Since volatile emissions are also dependent on the physiological state of the plant, we compared pheromone attraction in the background of both damaged and intact plants. Surprisingly, our results show that a natural odor bouquet does not influence flight behavior at all, although previous studies had shown a suppressive effect at the sensory level. We also chose different concentrations of single plant-emitted volatiles, which have previously been shown to be neurophysiologically relevant, and compared their influence on pheromone attraction. We observed that pheromone attraction in male moths was significantly impaired in a concentration-dependent manner when single plant volatiles were added. Finally, we quantified the amounts of volatile emission in our experiments using gas chromatography. Notably, when the natural emissions of host plants were compared with those of the tested single plant compounds, we found that host plants do not release volatiles at concentrations that impact pheromone-guided flight behavior of the moth. Hence, our results lead to the conclusion that pheromone-plant interactions in Heliothis virescens might be an effect of stimulation with supra-natural plant odor concentrations, whereas under more natural conditions the olfactory system of the male moth appears to be well adapted to follow the female pheromone plume without interference from plant-emitted odors.

Methyl salicylate and trans‐anethole affect the pheromonal activity of homofarnesal, the female sex pheromone of azuki bean beetle

“…), Heliothis virescens (Fabricious) (Badeke et al . ) and stink bugs Halyomorpha halys (Stal) (Zhang et al . ), among others, in which the effects in insects are modulated primarily by odorant receptors (Bohbot & Dickens ).…”

“…Previous reports have been published on the effects of plant components on the pheromone attractiveness of many field pests, including moth species Agrotis ipsilon (Hufnagel) (Deisig et al 2012;Renou et al 2015), Spodoptera spp. (Guerrero et al 2014), S. littoralis (Rouyar et al 2011;Hatano et al 2015;Renou et al 2015), Heliothis virescens (Fabricious) (Badeke et al 2016) and stink bugs Halyomorpha halys (Stal) (Zhang et al 2014), among others, in which the effects in insects are modulated primarily by odorant receptors (Bohbot & Dickens 2012). However, the effects on Ph-ORNs by the tested components are expected to be clarified by further studies.…”

Plant odor and sex pheromone are integral elements of specific mate recognition in an insect herbivore

“…; Badeke et al. ). A tentative explanation for this is that plant volatiles serve diverse behavioral roles, they signal plants for adult feeding, for mating or egglaying, or plants that that are not suitable as adult or larval food.…”

“…Curiously, the behavioral consequences of blending plant volatiles with sex pheromones differ among species and the plant chemicals investigated: plant volatiles can both synergize and antagonize the male response to sex pheromone (Dickens et al 1990;Light et al 1993;Yang et al 2004;Schmidt-Büsser et al 2009;Trona et al 2013;Badeke et al 2016). A tentative explanation for this is that plant volatiles serve diverse behavioral roles, they signal plants for adult feeding, for mating or egglaying, or plants that that are not suitable as adult or larval food.…”

“…Inadequate plant stimuli, signaling damaged plants or nonhost plants that are unsuitable for oviposition, antagonize the male response to pheromone (Hatano et al 2015;Badeke et al 2016;Wang et al 2016). This poses the question whether perception of host plant volatiles interacts with inadequate, heterospecific pheromone stimuli.…”