Entomophaga maimaiga is a Japanese fungus which has shown striking success in managing spongy moth populations in North America.

By 1912, they summarized their work, stating that extensive releases had never established this fungal pathogen, which they referred to as "gypsy fungus".

The fungus was determined to belong to the genus Entomophaga in the fungal order Entomophthorales and was given the name maimaiga based on geographical distribution.

In 1989, cadavers of spongy moths found hanging on tree trunks revealed large resting spores characteristic of entomophthoralean fungi.

The fungus spreads through aerial dispersion of actively ejected asexual spores from cadavers of spongy moth larvae it has killed.