Ken Raffa

Education:
PhD Entomology – Washington State University-Pullman, 1980
M.S. Entomology – University of Delaware, 1976
B.S. Biology – Saint Joseph’s College, 1972

Research Interests:
Our program addresses mechanisms that drive the population dynamics of forest insects, with special emphasis on plant-insect interactions, predator-prey relationships, and insect-microbial-symbioses. We investigate each within the context of host plant properties that affected herbivore behavior, reproduction, and susceptibility to natural enemies, as well as herbivore counter-adaptations against multiple ecological constraints. We analyze biological thresholds and cross-scale interactions in insect outbreaks. Our study systems involve insects that pose challenges to natural resource management, so this information can improve our ability to address invasive species, sustainable production systems, biodiversity, and global change.

Our recent research highlights include: 1) How host selection behavior of individual bark beetles varies with beetle population density and thereby generates positive feedback during transitions  from  non-outbreak to outbreak conditions. These behaviors involve genetic, environmental responses to host compounds; 2) How attraction by predators to chemical signaling among herbivores can drive biochemical counter-adaptations that allow partial escape while allowing intraspecific functionality; 3) The critical role of thresholds in linking patterns with processes of insect outbreaks, specifically that tree defense is a crucial determinant of whether outbreaks occur, yet  inconsequential after they do. 4) Beetles egest bacteria in oral secretions that inhibit opportunist fungi from exploiting host trees after their defenses are exhausted by beetle mass attacks; 5) Enteric gut bacteria are crucial to susceptibility of gypsy moth to the microbial pathogen Bt. Future research will expand our results on how microscale processes such as insect-symbiont-plant interactions can have landscape-scale outcomes.

All are collaborative projects, with interdisciplinary colleagues from UW depts. Forest & Wildlife Ecol, Plant Path, Microbio, and Zool, the US Forest Service, and various universities.

Research Category: Suborganismal, Organismal and Applied