One of the challenges in insect chemical ecology is to understand how insect pheromones are synthesised, detected and degraded. Genome wide survey by comparative sequencing and gene specific expression profiling provide rich resources for this challenge. A. ipsilon is a destructive pest of many crops and further characterization of the genes involved in pheromone biosynthesis and transport could offer potential targets for disruption of their chemical communication and for crop protection.

Odorant binding proteins (OBPs) and chemosensory proteins (CSPs) play essential roles in insect chemosensory recognition. Here, we identified nine OBPs and nine CSPs from the Myzus persicae transcriptome and genome. Genomic structure analysis showed that the number and length of the introns are much higher, and this appears to be a unique feature of aphid OBP genes. Three M. persicae OBP genes ( OBP3 / 7 / 8 ) as well as CSP1 / 4 / 6 , CSP2 / 9 and CSP5 / 8 are tandem arrayed in the genome. Phylogenetic analyses of five different aphid species suggest that aphid OBPs and CSPs are conserved in single copy across all aphids (with occasional losses), indicating that each OBP and CSP class evolved from a single gene in the common ancestor of aphids without subsequent duplication. Motif pattern analysis revealed that aphid OBP and CSP motifs are highly conserved, and this could suggest the conserved functions of aphid OBPs and CSPs. Three OBPs ( MperOBP6 / 7 / 10 ) are expressed antennae specifically, and five OBPs ( MperOBP2 / 4 / 5 / 8 / 9 ) are expressed antennae enriched, consistent with their putative olfactory roles. M. persicae CSPs showed much broader expression profiles in nonsensory organs than OBPs . None of the nine MperCSPs were found to be antennae specific, but five of them ( MperCSP1 / 2 / 4 / 5 / 6 ) showed higher expression levels in the legs than in other tissues. MperCSP10 mainly expressed in the antennae and legs. The broad and diverse expression patterns of M. persicae CSPs suggest their multifunctions in olfactory perception, development and other processes.

Recent studies have indicated that the plant volatile methyl benzoate (MB) exhibits significant insecticidal bioactivity against several common insects. However, the potential environmental hazards of MB and its safety to non-target organisms is poorly understood. In the present study, these characteristics were investigated through laboratory experiments and field investigations. The results revealed that MB was highly toxic to the agricultural pest, fall armyworm Spodoptera frugiperda. Compared with the commercial pesticide lambda-cyhalothrin, the toxicities of MB against S. frugiperda larvae and adults were comparable and 3.41 times higher, respectively. Behavioral bioassays showed that the percentage repellency of MB to S. frugiperda larvae was 56.72 %, and MB induced 69.40 % oviposition deterrence rate in S. frugiperda female adults. Furthermore, in terms of median lethal concentration (LC₅₀) and median lethal doses (LD₅₀), MB exhibited non-toxic effects on non-target animals with 3-d LC₅₀ of > 1 % to natural predators (Coccinella septempunctata and Harmonia axyridis), 3-d LD₅₀ of 467.86 µg/bee to the bumblebee Bombus terrestris, 14-d LC₅₀ of 971.09 mg/kg to the earthworm Eisenia fetida, and 4-d LC₅₀ of 47.30 mg/L to the zebrafish Brachydanio rerio. The accumulation of MB in the soil and earthworms was found to be extremely limited. Our comparative study clearly demonstrated that MB is effective as a selective botanical pesticide against S. frugiperda and it is safe to use in the tested environment, with no toxic effects on non-target animals and natural predators.