Eavesdropping on Plant Volatiles by a Specialist Moth: Significance of Ratio and Concentration

Abstract

We investigated the role that the ratio and concentration of ubiquitous plant volatiles play in providing host specificity for the diet specialist grape berry moth Paralobesia viteana (Clemens) in the process of locating its primary host plant Vitis sp. In the first flight tunnel experiment, using a previously identified attractive blend with seven common but essential components (“optimized blend”), we found that doubling the amount of six compounds singly [(E)- & (Z)-linalool oxides, nonanal, decanal, β-caryophyllene, or germacrene-D], while keeping the concentration of other compounds constant, significantly reduced female attraction (average 76% full and 59% partial upwind flight reduction) to the synthetic blends. However, doubling (E)-4,8-dimethyl 1,3,7-nonatriene had no effect on female response. In the second experiment, we manipulated the volatile profile more naturally by exposing clonal grapevines to Japanese beetle feeding. In the flight tunnel, foliar damage significantly reduced female landing on grape shoots by 72% and full upwind flight by 24%. The reduction was associated with two changes: (1) more than a two-fold increase in total amount of the seven essential volatile compounds, and (2) changes in their relative ratios. Compared to the optimized blend, synthetic blends mimicking the volatile ratio emitted by damaged grapevines resulted in an average of 87% and 32% reduction in full and partial upwind orientation, respectively, and the level of reduction was similar at both high and low doses. Taken together, these results demonstrate that the specificity of a ubiquitous volatile blend is determined, in part, by the ratio of key volatile compounds for this diet specialist. However, P. viteana was also able to accommodate significant variation in the ratio of some compounds as well as the concentration of the overall mixture. Such plasticity may be critical for phytophagous insects to successfully eavesdrop on variable host plant volatile signals.

Plant Volatiles Enhance Behavioral Responses of Grapevine Moth Males, Lobesia botrana to Sex Pheromone

“…This fits well with release rates of compounds from grapevine inflorescences and berries (Tasin et al, 2006;Anfora et al, 2009). (E)-β-Caryophyllene increased attractiveness of pheromone over a wider range of release rates than the other compounds tested, indicating that grapevine moth males might be able to accommodate substantial variation in the amounts of some compounds, as shown for DMNT in the moth Paral-obesia viteana (Cha et al, 2011).…”

Monitoring Grape Berry Moth (Paralobesia viteana: Lepidoptera) in Commercial Vineyards using a Host Plant Based Synthetic Lure

“…For traps with synthetic host plant-based lures, a relatively low dose was used for the top three septa (13-C blend ϭ 168.5 g/septa, 7-C blend ϭ 112.5 g) and a relatively high dose (13-C blend ϭ 337.5 g, 7-C blend ϭ 225 g) was used for the bottom three. The two different doses are within the range of doses that female grape berry moth is attracted to in the ßight tunnel (Cha et al 2011). The high concentration lure was expected to stay attractive longer than the low concentration lure in the Þeld.…”

Season-Long Volatile Emissions from Peach and Pear Trees In Situ, Overlapping Profiles, and Olfactory Attraction of an Oligophagous Fruit Moth in the Laboratory

“…One way to deal with variations in plant volatile blends is to respond to a specific set of compounds common to all host plants (Rajapakse et al 2006;Leppik and Frérot 2012). Female insects are expected to tolerate a certain modulation of the ratios of these common compounds within distinct threshold values, as recently shown for two tortricid moth species (Cha et al 2010;Najar-Rodriguez et al 2010.…”

“…Herbivores with multiple generations per year that reproduce on different hosts are confronted with substantial variations in the volatile blends emitted by their different host plant species at particular periods in time, as well as by the same plant species across a growing season (Piñero and Dorn 2009;Tasin et al 2010). Thus, the insects' odorguided behavior must be adapted to respond to essential constituents of volatile blends and to the natural variations of these blends (Tasin et al 2007;Cha et al 2010;NajarRodriguez et al 2010NajarRodriguez et al , 2011. One way to deal with variations in plant volatile blends is to respond to a specific set of compounds common to all host plants (Rajapakse et al 2006;Leppik and Frérot 2012).…”