Kay, Sasha (2013-12). The Effects of 'Candidatus Liberibacter solanacearum' on Coccinellid Predation of the Potato Psyllid and Intraguild Interactions between Psyllids and Aphids on Tomato. Master's Thesis.
'Candidatus Liberibacter solanacearum' (Lso), a pathogen of many solanaceous crops, and its insect vector, Bactericera cockerelli, are increasing their geographic range in North America, Central America, and abroad. Understanding the mechanisms by which their range is expanding will be key to both pest and disease management. This study aimed to determine if Lso could protect its insect vector from predation by Hippodamia convergens by examining beetle preference for infected tomato and/or insect volatile combinations in a 2-choice olfactometer, and the consumption of uninfected and Lso-infected psyllids in a no-choice feeding bioassay. Additionally, a previously unreported aphid facilitation interaction between the psyllid and Myzus persicae on tomato was examined to determine if either plant infection by Lso or the presence of the psyllid could promote aphid facilitation. Beetles significantly preferred the odors of uninfected tomato to those of infected tomato, but their preference was insignificant when both plants were infested with psyllids. Beetle consumption of psyllids did not vary significantly according to their infection status. Lso may confer slight indirect protection to its insect vector through modification of their shared host plant. The presence of the psyllid, rather than plant infection by Lso, was determined to be responsible for aphid facilitation on tomato. Aphid populations persisted for 30 days or longer on plants with psyllids. Aphid populations increased on psyllid-infested plants upon which the majority of psyllids were young nymphs, and that had previously been infested with aphids.