Over what distance are plant volatiles bioactive? Estimating the spatial dimensions of attraction in an arthropod assemblage

Abstract

As studies demonstrating attraction of natural enemies to synthetic herbivore‐induced plant volatiles (HIPVs) accumulate, it is becoming increasingly important to investigate how deployment of these compounds influences arthropod behavior and distribution in the field. There is currently an unexplained dichotomy in the literature regarding the distance over which HIPVs are thought to be effective. It is assumed that these compounds increase recruitment of natural enemies into fields, whereas experiments have found the effects of attraction to dissipate as little as 1.5 m from lures. Through the use of the common HIPV phenylethyl alcohol in soybean [Glycine max (L.) Merr (Fabaceae)] fields, we used replicated mini plots to test the spatial scale and consequences of attraction by analyzing the response of a complex arthropod community to HIPVs along a distance gradient from the HIPV source. Although repellent effects were more common than attractive ones, we found that insect responses to HIPVs are generally consistent out to a range of 8 m, corroborating the idea that volatiles can influence a wide area and are capable of increasing arthropod recruitment at a field scale. Evidence of redistribution (i.e., depletion of patches surrounding HIPV‐augmented plots) was found for a single taxon, braconid wasps, for which augmentation occurred around the lure, but with a reciprocal decline in abundance at greater distances from the emission site. These results are both encouraging and cautionary. Although broad‐scale diffusion of HIPVs appears to be common, redistribution of key predators and/or parasitoids may complicate natural enemy management on a landscape scale by aggravating pest outbreaks in areas robbed of their normal carnivore assemblage.

Potential for Using Acetic Acid Plus Pear Ester Combination Lures to Monitor Codling Moth in an SIT Program

“…Plant volatile kairomones are generally thought to have sampling ranges of perhaps 5–10 m [28,29,30]. Given this fact, and the argument that short-range lures have a higher probability of estimating S:W ratios near the site a wild insect is caught, AA-PE lures should offer greater chances than pheromone lures of measuring localised S:W ratios and correlating codling moth trap catches with damage in localised areas.…”

Spatial analysis of mass trapping: how close is close enough?

“…Communication distances, like atmospheric pheromone concentration studied in mating disruption, will vary as a function of wind speed, vertical leaf area density, canopy form and other factors, but recent evidence suggests that plant volatiles can operate over attraction distances as great as 8 m, as in the case of a range of arthropod taxa in soybeans . Several authors have considered adequate separation to avoid interference between such plant volatile treatments to be between 10 and 35 m .…”

Herbivore-induced plant volatiles in natural and agricultural ecosystems: open questions and future prospects

“…However, we currently have only limited understanding of how such factors influence HIPV signaling in specific settings, although somewhat more work has explored the implications of local atmospheric conditions and habitat structure on the transmission of insect pheromones [37,39]. Furthermore, we also know relatively little about the concentrations of HIPV emissions to which receiving plants and insects are exposed in nature [26 ] or the typical and maximal distances over which HIPV mediated signaling interactions occur under field conditions [40]. We can, however, certainly infer that receivers of HIPV cues that are highly mobile, including many insect species, will benefit from the perception of such cues over greater distances than more sedentary receivers such as plants (particularly where HIPV function mainly as within-plant signals).…”