1st Place: Using herbivore-Induced plant volatiles to improve sugarcane aphid management in sorghum

Planting resistant crop cultivars is a useful tactic for reducing pest damage in the field. Recent research, however, has demonstrated that some crop cultivars can attract natural enemies when infested with pests, thereby leading to indirect pest suppression. Herbivore-induced plant volatiles (HIPVs) are emitted by plants and act as odor cues in the environment for natural enemies. Despite their potential to facilitate biological control and reduce insecticide use, HIPVs have yet to be applied in many IPM programs. The sugarcane aphid (Melanaphis sacchari Zehntner) is an invasive pest that greatly affects sorghum production and current pest management heavily relies on insecticide applications. Our study aimed to quantify HIPV production in multiple cultivars, quantify natural enemy attraction to HIPVs in the laboratory, and determine how differences in HIPV production affect natural enemy attraction. In olfactometer bioassays, we found that parasitoid wasps (Aphelinus nigritus) were attracted to HIPVs produced by a resistant aphid-infested cultivar of sorghum (ATx3409/RTx436), whereas other aphid-infested sorghum cultivars were not preferred by natural enemies (DKS38-16). Collections of HIPVs showed that ATx3409/RTx436 produced significantly higher concentrations of methyl salicylate (a highly attractive HIPV) when infested with aphids, whereas DKS38-16 produced little methyl salicylate. Field studies found that ATx3409/RTx436 had a higher natural enemy to aphid ratio and maintained pests below the action threshold for a longer period of time when compared to DKS38-16. This work indicates that sorghum varieties that produce HIPVs to attract natural enemies should be incorporated into sugarcane aphid IPM programs.