Observations by other workers concerning the effects of sunlight, temperature, water-humidity, substrate, and chemicals or the persistence of microsporidian spores are briefly reviewed. The results of studies on the influence of the factors listed above on the survival of Nosema necatrix spores are also presented. Dry N. necatrix spores cannot withstand direct sunlight or temperatures greater than 40°C for more than a few hours. Drying is detrimental to spore longevity. Exposure to 0.26% sodium hypochlorite or 50% ethyl alcohol completely destroys spore viability.