Behavioural and chemical mechanisms of plant‐mediated deterrence and attraction among frugivorous insects

Abstract

1. Herbivory often induces systemic plant responses that affect the host choice of subsequent herbivores, either deterring or attracting them, with implications for the performance of both herbivore and host plant. Combining measures of herbivore movement and consumption can efficiently provide insights into the induced plant responses that are most important for determining choice behaviour.2. The preferences of two frugivorous stink bug species, Nezara viridula and Euschistus servus between cotton plants left undamaged or damaged by Helicoverpa zea and Heliothis virescens larvae were investigated. A novel consumer movement model was used to investigate if attraction rates or leaving rates determined preferences. Stink bug consumption rates were measured using salivary sheath flanges. Finally, the systemic induction of selected phenolic‐based and terpenoid secondary metabolites were measured from heliothine herbivory on developing cotton bolls, to investigate if they explained stink bug feeding responses.3. Heliothine herbivory did not affect the N. viridula feeding preference. However, we found opposing effects of H. zea and H. virescens herbivory on the behaviour of E. servus. Avoidance of H. zea‐damaged plants is not obviously related to phenolic or terpenoid induction in cotton bolls; whereas a preference for H. virescens‐damaged plants may be related to reductions in chlorogenic acid in boll carpel walls.4. The present results highlight the inferential power of measuring both consumer movement and consumption in preference experiments and combining behavioural responses with phytochemical responses. Furthermore, while plant‐mediated interactions among herbivorous insects are well studied, interactions among frugivorous species specifically have been poorly documented.

Competitive release and outbreaks of non‐target pests associated with transgenic Bt cotton

“…Similarly, H. zea herbivory increased E. servus leaving rates from both damaged and nearby undamaged plants (Zeilinger et al. ). The prevailing evidence makes clear that under heavy to moderate H. zea infestations, non‐ Bt cotton fields constitute patches of poorer average host quality and greater host heterogeneity for E. servus relative to Bt cotton fields.…”

“…We calculated the effect size as Hedges's d from competition experiments described in Zeilinger et al. (, ). Each species combination consisted of n = 4 effect sizes, except the N. viridula and H. virescens combination in which n = 3.…”

“…To assess competitive effects from heliothine larvae (H. zea and H. virescens) on stink bug performance (E. servus and N. viridula), we compiled previously published results on their interactions into a meta-analysis. We calculated the effect size as Hedges's d from competition experiments described in Zeilinger et al (2011Zeilinger et al ( , 2015. Each species combination consisted of n = 4 effect sizes, except the N. viridula and H. virescens combination in which n = 3.…”

“…Moreover, the species‐specific and multi‐scale nature of these interactions indicate that they are mediated by induced resistance in the shared host plant (Zeilinger et al. ).…”

“…If so, competitive release may play an important role in stink bug outbreaks in Bt cotton. Herbivory by H. zea larvae on non-Bt cotton plants reduces nymphal growth rates of E. servus by 36% at within-plant scales and deters feeding by E. servus nymphs at the whole-plant scale (Zeilinger et al , 2015. Moreover, the speciesspecific and multi-scale nature of these interactions indicate that they are mediated by induced resistance in the shared host plant (Zeilinger et al 2015).…”