My lab studies the ecology and evolution of plant-pathogen interactions within natural and agricultural ecosystems. There are four active projects in the lab at this time. My graduate students, Jessica Cook and Erin Mason, are investigating the long-term effects of epidemics by a systemic rust pathogen (Uromyces ari-triphylli) on its host, Arisaema triphyllum (Jack-in-the-pulpit). This work aims to investigate the effects of infection on the fitness of individuals, and also evaluates how epidemics affect population size and persistence. Work on individuals has found that infection has multiple negative effects; infected plants grow more slowly, have lower reproductive rates and lower survivorship. Preliminary analyses for population effects indicate that population growth rates are negatively correlated with disease incidence (i.e., The proportion of the individuals infected within a population).

We are also investigating the three trophic level interaction between the American chestnut, its blight pathogen and an intracellular hyperparasite that alters virulence when infecting the pathogen. A major aspect of this work has been to evaluate how the host population responds when a pathogen changes virulence. My lab has published on the theoretical and empirical aspects of hyperparsite invasion on host population size and structure. We are also interested in the use of hyperparasites as biological control agents. Collaborative work with researchers at Michigan state University, West Virginia University, the University of Texas-Pan American, and the Wisconsin Department of Natural Resources is aimed at developing methods to enhance and protect chestnut populations using the hyperparasite.

A new interest is the evolution of fungicide resistance. We are using the apple scab pathogen, Venturia inaequalis, as a model system. This relatively new work will evaluate spray programs for their effectiveness in delaying or inhibiting the evolution of fungicide resistance. One important aspect of this work may be the apparent synergy between resistance mechanisms, whereby evolution of resistance to one class of fungicides may enhance the probability that a pathogen will evolve resistance to other fungicides.

The fourth project is investigating the population structure of the wheat scab pathogen, Gibberella zeae, in Nepal and the United States. The population in Nepal was found to be highly variable. Samples from a 25 Km2 area contained more genetic variability than the G. zeae population in all of North America. Thus, the Nepalase population may act as a source population for new genetic variants that may differ in both toxin production and virulence. The work on populations in the United States is aimed at investigating the scale of population diversity and identification of inoculum sources.