The potential usefulness of Nosema locustae Canning as a microbial agent for grasshopper control was first demonstrated by Henry (1971) and Henry et al. (1973). These authors found that a 50–60% reduction in grasshopper density (as compared with untreated populations) could be achieved, and they speculated that 35–50% of the survivors would be sufficiently infected so that their fecundity would be reduced. The value of incorporating such an agent into a grasshopper pest-management system is obvious: By suppressing high insect densities to manageable levels, the need for conventional chemical insecticides could be reduced and perhaps even restricted only to “hot spot” areas. The objectives of the study we report here were to: (1) Determine if N. locustae was infective to the predominant species of grasshoppers in Saskatchewan; (2) if so, monitor the development of the disease within the populations; and (3) determine if the pathogen could survive over the winter and infect next year's populations. Because this was a preliminary experiment, we did not attempt to determine any effect the pathogen might have on population reduction.