Life Cycle of the Entomophaga maimaiga

An example of an insect pathogen that has been successfully controlling its host is the fungus Entomophaga maimaiga, a pathogen of the gypsy moth. This fungus was introduced about 1911, but was not recovered in forests until 1989, when it was widespread and abundant in New England. It has continued to control New England gypsy moth populations for several years. It overwinters in leaf litter as resting spores, which germinate when gypsy moth larvae are present. Newly hatched caterpillars are dispersed by wind, and those that fall to the forest floor are probably infected while crawling to a tree. While these larvae are feeding in the tree canopy, if there is enough rainfall, the fungus in their bodies produces spores that spread to other caterpillars. If conditions are right, this infection cycle occurs again during the larval stage. Large caterpillars rest during the day in forest litter, where they are also susceptible to infection. In late June, as infected caterpillars die in large numbers, new resting spores are produced to survive the next winter. This biological control process depends on well-timed rainfall to be successful.