Nosema fumiferanae may be transmitted perorally, transovarially, or by injection into its hostChoristoneura fumiferana. Infected females, but not infected males, readily transmit the parasite to their offspring. Ingestion of diet, surface treated with 105N. fumiferanae spores per 7.0 cm2, resulted in sublethal infection in adults, and reduced the number of hatchable eggs by 19%.