Aphids are one of the worlds most important agricultural pests. They are both direct pests and vectors of viral plant pathogens. We work on aphids both in the contect of vector biology and pest managment.
Psyllids or "jumping plant lice" are small insects related to aphids and leafhoppers. They are also known to be vectors of bacterial pathogens. We study two species of psyllid in our lab.
Cottony Ash Psyllids are a poorly studied species that is invasive to Canada and the Norther Great Plains of America. These insects are associated with massive losses of black and manchiruan ash trees. Since these trees are common to urban forests in prarie Canada, these are in important pest.
The second species we study is the tomato/potato psyllid, Bactericera cockerelli. Potato psyllids vector the endosymbiotic bacteria Candidatus Liberibacter solanacearum (Lso), which causes diseases in various solanaceous plants. Recent work has revealed multiple haplotypes/biotypes for both the psyllid and the bacteria. The psyllid haplotypes are strongly associated with specific geographic regions, and various biological traits vary along with haplotype. The potato psyllid is also unusual in having a wide host range that encompasses over 40 plant species, while most psyllids have only one or a few potential hosts. I am currently examining aspects of host plant choice in the context of these different haplotypes and when psyllids are, or are not, infected with Lso. This will lead to a greater understanding of patterns of host use, local adaptation, and how endosymbionts affect host use. A second focus of my current psyllid work is how pathogens influence the psyllid’s host choice decisions, either directly or as mediated through plants. In this context, I am using the psyllid system to answer questions about trophic and community level implications of pathogens. This is a mostly unstudied aspect of ecology and has implications for disease ecology and epidemiology. It is especially important in the context of climate change, which has made it possible for vectors and pathogens to extend their ranges.
A final aspect of this work is the management of potato psyllids. Currently, psyllids are managed using multiple pesticide applications. However, in many regions, potatoes require little pesticide input, because natural enemies sufficiently control pests. Unfortunately, the threat of infection with Lso results in aggressive management on the part of growers. I have been examining ways to reduce or limit pesticide use, to manage insecticide resistance, and to make treatment decisions that preserve beneficial insects and natural enemies. Additionally, potato psyllids are related to the Asian Citrus Psyllid (ACP), which also carries a pathogenic Liberibactor, and thus is a major threat to the citrus industry worldwide. Because the potato psyllid is easier to rear an work with, we often use it as a proxy for answering question about ACP management and general psyllid biology.
Our lab is interested in numerous topics surrounding bees and pollination. We are particularly curious about pollination in agricultural contexts, especially in poorly studied cropping systems. While a second line of research examines pollinator communities in different landscape contexts. We are broadly intersted in develping methods to help growers balance pest control, disease managenemt, and pollinator health.
More fundamental projects in our lab are focussed on multitrophic interactions among plants, insects, and micorbes.
In the past, our research on bees was focused on aspects of behavioural ecology, in particular social interactions. This is no longer one of our research focuses.
We are generally interested in how insects choose hosts and prey. Theory suggests that animals should be careful about selecting where to lay their eggs and what prey items they pursue. Females are expected to optimize their fitness by choosing those hosts that are best for their offspring. This principal applies to herbivores and also to parasitoids. We are interested in how changes in physiological state, such as starvation or age influences host choices. Dr. Prager and his colleagues demonstrated that in a species of parasitoid with a narrow host-range, host species preference does not change despite the parasitoid’s condition, but host choice is influenced by egg load. This goes somewhat counter to theory, which predicts that a female insect that anticipates dying will be less choosy. This finding has interesting implications for the evolution of host preference, for invasive species management, for the use of parasitoids in biological control, and for community structure.
None of our current projets at the U of S involve mosquitoes. However, in the past lab members have studied population biology and ecology of treehole mosquitoes in the genus Aedes, effetcs of pollution on vectors of West Nile Virus, and novel control methods of multiple species of medical importance. One recent project, conducted with collaborators at UC Riverside examines the effects of Pharmaceutical and Personal Care Products (PCPPs) on insects, and across trophic levels. PCPPs are common materials used by humans that are not removed in typical waste processing. Consequently, when wastewater is reused for irrigation, or escapes into the environment, various organisms can be exposed. This includes mosquitoes that breed in the pools of standing water. We are examining the effects of these PCPPs on the development and microbial communities of mosquitoes that develop in these pools.
Spider mites are a large family that includes over 1000 species. These athrropods are pests on numerous crops including: many fruit trees, vines, berries, vegetables, corn, cotton and ornamental plants. Further, they have rather complex interactions with plants such that abiotic factors such as drought stress can influence them with the plant serving as a mediator. One way of managing spider mites, espeically in greenhouses, is through predactory mites in the genus Phytoseiulus. We are intersted in how biologcai control agents, abiotic factors, and spider mites interact and the implications of these interactions on management.