Platydema waterhousei is a beetle that infests the economically important Rishi mushroom. The toxic effects of four controlled atmospheres to each of the life stages of Platydema waterhousei were investigated. The atmospheres used were 100, 80, 60, and 0% CO 2 with N 2 making up the remainder. The atmosphere containing 80% CO 2 was more toxic to eggs than pure CO 2 and N 2 . Pure CO 2 was the most lethal to larvae, pupae, and adults. Pupae were the most resistant life stage to all treated gases. Adults were more sensitive than eggs and larvae in pure CO 2 and N 2 atmospheres. Adults as well as eggs were more susceptible than larvae when they were exposed to 60% CO 2 . Eggs were more sensitive than adults and larvae when they were held under 80% CO 2 . The best control of all life stages could be achieved by exposing to 80% CO 2 for 3 days or to 100% CO 2 for 4 days.