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Harvard Forest REU Symposium Abstract 2019

  • Title: The very hungry, lonely, and sick caterpillar: exploring pathogen occurrence within low-density populations of gypsy moth
  • Author: Savanna Brown (Bowling Green State University - Main Campus)
  • Abstract:

    Gypsy moth (Limantria dispar) has successfully invaded a large portion of North America in a matter of decades, damaging a variety of temperate forest tree species and costing billions of dollars annually in preventative and remediation costs. In 1989 a fungal pathogen native to Japan, Entomophaga maimaiga, was accidentally established in North America and may have fundamentally changed the population dynamics of gypsy moth. Although some data exists on pathogen dynamics in high-density outbreak systems, few studies have been done since the introduction of E. maimaiga to determine its role in preventing outbreaks and maintaining populations of gypsy moth at low densities. I performed a mortality analysis of gypsy moth larvae in 7 sites at the Quabbin Reservoir in Central Massachusetts in 2019, where after 2-3 years of outbreak populations, larval densities have declined considerably. In spring before neonates hatched, egg mass density was recorded as a proxy of population density at each site. Recording larval mortality and cause of death allowed us to observe if E. maimaiga played a unique role among several contemporaneous pathogens and parasitoids in maintaining equilibrium in low density populations. Analysis of larval mortality using marginal attack rates indicated that larval mortality from E. maimaiga was proportionally higher in populations with lower egg mass densities. Additionally, of the mortality agents tested, rate of infection by E. maimaiga was most strongly correlated with beginning egg mass density of each population.

  • Research Category: Group Projects; Invasive Plants, Pests & Pathogens