Zygomycota

The Order Entomophthorales in the Zygomycota contains many species of fungi that are important regulators of insect populations. The life cycle of species in this order is more complex than that of the asexual cycle of the Ascomycota. A typical entomophthoralean species includes thick-walled environmentally resistant resting spores and short-lived infectious primary conidia. Because the primary conidia are forcefully discharged, the dead infected host is often surrounded by a ring of the discharged conidia. A halo of these conidia around flies that died from Entomophthora muscae infections can often be seen, especially on glass windows. Hence this fungus is often called the “window pane fungus.”

Many insect species are infected by entomophthoralean fungi and they may act as important natural control agents, producing epizootics. Insects killed by entomophthoralean fungi usually climb to the tops of plants to die, a behavior called “summit disease.” When producing resting spores the dead hosts usually appear to be lighter or some color not typical of healthy hosts and are often slightly bloated; when producing conidia, they appear lighter in color and are covered with an obvious coating of fungal structures often localized in bands over intersegmental membranes. Grasshoppers infected with Entomophaga grylli and clover leaf weevils infected with a Zoophthora species are often encountered in the field. Entomophthoraleans are important natural enemies for both these insect species. A particularly virulent and host specific species, Entomophaga maimaiga, infects gypsy moths and is, in some areas of the Northeast, suppressing populations of this oak pest.

The majority of biological control efforts using Entomophthorales species have been focused on introductions of the pathogens into naïve host populations or augmentation and of conservation through management practices.