UC Riverside

Aphids are small phloem sap-feeding pests, which transmit economically damaging plant viruses. Natural enemies are used as an environmentally sustainable method of aphid control, and can have either (1) consumptive effects: the consumption of the prey or (2) non-consumptive effects: the change in behavior, reproduction, or morphology in response to predation risk. Non-consumptive effects can be induced when a prey species perceives a predator. Prey often rely on chemical cues to detect predation risk. Lady beetles, generalist predators of aphids, deposit hydrocarbons while walking. Insects can respond to the chemical cues of predators by altering either their movement or feeding behavior, however, the latter has not yet been explored in aphids. Aphids may alter dispersal and feeding behaviors in response to detection of a predator cue. This non-consumptive effect could enhance or suppress virus transmission. Non-consumptive effects are vastly understudied, and have the potential to be equally important in shaping predator-prey dynamics compared to consumptive effects. In this thesis, I investigate the hypothesis that an important aphid pest (Myzus persicae) changes its movement and feeding behavior in response to hydrocarbons deposited by a key natural enemy, the convergent lady beetle, Hippodamia convergens. Using gas-chromatography and mass-spectrometry, I identified the chemical components in the H. convergens footprints, which include several straight-chained hydrocarbons: tricosane, pentacosene, pentacosane, heptacosene, heptacosane, and nonacosene. Using dispersal assays, I found that M. persicae disperse from areas exposed to H. convergens cues similarly to aphids dispersing from areas treated with mineral oil, a plant surface treatment that deters feeding by piercing-sucking insects. However, M. persicae did not change its in-leaf feeding behavior when forced to feed on leaves treated with lady beetle “footprints”. Based on the results of this thesis, we found that aphids exposed to predation risk will increase their dispersal which has implications for pathogen spread.