Predicting When, Why and Where Asian citrus psylllids move to increase effectiveness of insecticide sprays

Predicting When, Why and Where Asian citrus psylllids move to increase effectiveness of insecticide sprays

Report Date: 10/03/2016
Project: 15-024   Year: 2016
Category: ACP Vector
Author: Lukasz Stelinski
Sponsor: Citrus Research and Development Foundation

We have continued to investigate movement of Asian citrus psyllid (ACP) as it relates to biotic and abiotic factors. Climate change increases the duration and intensity of heat waves, causes earlier spring arrival, and more frequent drought stress events. We investigated the response of ACP and its parasitoid to pathogen and herbivore-induced plant volatiles released from plants with and without drought stress. ACP vectors were attracted to headspace volatiles of CLas-infected citrus plants at 95% of their water holding capacity (WHC); such attraction to infected plants was much lower under drought stress. Attraction of the vector to infected and non-stressed plants was correlated with greater release of methyl salicylate (MeSA) as compared with uninfected and non-stressed control citrus plants. Drought stress abolished MeSA release from CLas-infected plants as compared with non-stressed and infected plants. Similarly, the parasitoid wasp, Tamarixia radiata, was attracted to headspace volatiles released from ACP-infested citrus plants at 95% of their water holding capacity (WHC). However, wasps did not show preference between headspace volatiles of psyllid-infested and uninfested plants, when they were at 35% WHC, suggesting that herbivore-induced defenses did not activate to recruit this natural enemy under drought stress. We also investigated learning in ACP as it relates to movement. In ACP, which mate throughout their lives, learning in the context of sexual behaviors may increase the likelihood of successful mating. In females, two aspects of behavior were investigated: 1) the influence of natal host species on adult settling and oviposition host preference, and 2) the effect of the initial mating experience on future mate selection. In males, we investigated whether female odor is learned after mating experience. Our results indicate that females prefer to oviposit onto host plants similar to their own natal environment. However, this only occurs when the natal host plant may be associated with fewer plant defence compounds than the alternative host species. Females also demonstrate the ability to discriminate between males based on abdominal color and later avoid males bearing certain traits, perhaps associated with reproductive immaturity. Additionally, male psyllids appear to learn odors associated with receptive females. We conclude that in ACP, learning may modulate oviposition preference and mate choice in females, and male recognition of female conspecifics. These data suggest an adaptive significance of learning in the context of reproduction and that learning may increase the likelihood of successful reproduction in ACP.


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