Pest Control Compounds Targeting Insect Chemoreceptors: Another Silent Spring?

Abstract

An emerging concept in the ongoing battle against insect pests is that compounds that influence the behavior of insects by modulating their ability to smell could be developed by targeting their chemoreceptors. This idea was identified by the annual horizon scan of global conservation issues as a topic of concern for their 2015 report. Unfortunately, the publication could only afford a short discussion of the pros and cons of the approach. Here we review the concept and discuss how it might be best implemented to avoid potential off-target effects and environmental harm. We describe the first of this class of compounds, VUAA1, outlining that its highly broad range of potential insect targets would lead to many of the issues associated with broad-spectrum insecticides. We also review compounds and approaches targeting the relatively less conserved carbon dioxide receptor complex and finally highly tuned receptors to conclude that focusing on species-specific pheromone receptors would result in fewer potential off-target effects.

Putative ligand binding sites of two functionally characterized bark beetle odorant receptors

“…In light of the intensifying outbreaks, more efficient control and detection of bark beetles are needed. One avenue forward is to exploit their odorant receptors (ORs) 4 , which detect olfactory information crucial for successful mate and host finding and used to coordinate attacks on trees.…”

“…Current knowledge of the molecular and functional evolution of the ORs as well as the ligand-OR interaction is however limited, yet crucial for understanding insect chemical ecology and species-specific sensory adaptations. From an applied perspective, functional characterization of ORs and determination of their binding sites are pertinent in pest insects, because receptors that are key to survival and reproduction represent potential targets for improved pest control using OR antagonists and agonists 4 . Also, with the advancement of biosensor technology towards using ORs to detect insect semiochemicals [15][16][17] , employing receptors tuned to the characteristic odors of a pest, such as bark beetle aggregation pheromones, could be useful for early detection of infestations.…”

Molecular characterization and evolution of a chemosensory receptor gene family in three notorious rice planthoppers, Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus, based on genome and transcriptome analyses

“…Insects rely on sensitive chemosensory systems to accomplish many crucial behaviors, such as locating and selecting hosts, mating, and avoiding predators . In many insects there are three types of chemosensory receptors: odorant receptors (ORs), ionotropic receptors (IRs) and gustatory receptor (GRs).…”

“…In many insects there are three types of chemosensory receptors: odorant receptors (ORs), ionotropic receptors (IRs) and gustatory receptor (GRs). The cells housing these receptor genes are mainly found in antennae, maxillary and labial palps that are covered by hair‐like structures termed sensilla …”

Inhibition of insect olfactory behavior by an airborne antagonist of the insect odorant receptor co-receptor subunit

“…However, widespread and indiscriminant use of such Orco directed compounds would be a cause for concern [58, 59]. Broadly active Orco antagonists would be unsuitable for agricultural use, as both pests and pollinators would be affected.…”