Several species of entomophthoraceous fungi have been reported infecting potato-infesting aphids in Maine (Patch 1907, Shands et al. 1962, 1963, 1972), but their impact on the populations has been variable (Shands et al. 1958). Because these fungi have been recorded as causing dramatic reductions in aphid populations, they are potential biological control agents in an integrated pest management system. Their utilization must take into consideration their compatibility with pesticides; on potatoes in Maine, for instance, it would be unreasonable to abandon the use of fungicides against early and late blight (c.a. Alternaria solani [Ellis and Martin] Jones and Grant andPhytophthora infestans[Mont.]dBy). It would be especially important to select a fungicide that would control blights without inhibiting the spread of insect-attacking fungi.