Exposure of Solidago altissima plants to volatile emissions of an insect antagonist ( Eurosta solidaginis ) deters subsequent herbivory

Abstract

Recent work indicates that plants respond to environmental odors. For example, some parasitic plants grow toward volatile cues from their host plants, and other plants have been shown to exhibit enhanced defense capability after exposure to volatile emissions from herbivore-damaged neighbors. Despite such intriguing discoveries, we currently know relatively little about the occurrence and significance of plant responses to olfactory cues in natural systems. Here we explore the possibility that some plants may respond to the odors of insect antagonists. We report that tall goldenrod (Solidago altissima) plants exposed to the putative sex attractant of a closely associated herbivore, the gall-inducing fly Eurosta solidaginis, exhibit enhanced defense responses and reduced susceptibility to insect feeding damage. In a field study, egg-laying E. solidaginis females discriminated against plants previously exposed to the sex-specific volatile emissions of males; furthermore, overall rates of herbivory were reduced on exposed plants. Consistent with these findings, laboratory assays documented reduced performance of the specialist herbivore Trirhabda virgata on plants exposed to male fly emissions (or crude extracts), as well as enhanced induction of the key defense hormone jasmonic acid in exposed plants after herbivory. These unexpected findings from a classic ecological study system provide evidence for a previously unexplored class of plant-insect interactions involving plant responses to insect-derived olfactory cues.plant defense | plant olfaction

Priming for Enhanced Defense

“…Recently, it was reported that a putative sex attractant of male goldenrod gall flies primed tall goldenrod for enhanced defense responses (e.g., JA production) and augmented resistance to feeding damage by goldenrod leaf beetle (35). This finding disclosed a novel type of plantinsect interaction in which the plant perceives olfactory cues from a coevolved herbivore.…”

Evidence For Plant-mediated Competition Between Defoliating and Gall-forming Specialists Attacking Solidago altissima

“…Dense outbreaks resulting in complete defoliation lead to mass exodus of adult beetles which then go on to oviposit in the soil of other patches (Morrow et al, 1989). Third, the preference of E. solidganis and the performance of Trirhabda on goldenrod clones differing in induced defenses both appear to respond in the same direction (Helms et al, 2013).…”

“…But insect herbivory can have a multitude of possible effects on host plant physiology (Karban and Baldwin, 1997), and Trirhabda folivory has previously been shown to affect Solidago leaf quality (Brown and Weis, 1995). A recent study by Helms et al (2013) also demonstrates a potentially strong role of induced defenses in S. altissima, with herbivore cues eliciting a strong up-regulation of jasmonic acid production. We hypothesize the effect of high levels of folivory by Trirhabda defoliation on the reactive tissue utilized by E. solidaginis may interfere with gall induction.…”

The raison d'être of chemical ecology

“…How rapidly a plant detects and responds to a pathogen can make the difference between resistance and susceptibility (Greenberg 1997), and rapid detection may also be important in defense against herbivores. For example, goldenrod plants can detect sex pheromones from herbivorous flies (Helms et al 2013), and Arabidopsis responds to chemicals in the slime of herbivorous slugs (Orrock 2013) as advance warning of future herbivory. These recent discoveries exemplify that diverse and currently under-studied index cues from attackers provide information in plant-herbivore-pathogen interactions.…”