The Comstoek mealybug (Pseudococcus comstocki) has been, since 1934, a serious pest of apples in Virginia. In some instances the injury has been pronounced for 1 or more yrs. followed by a period in which the injury was extremely light. During the seasons of 1940, 1941, and 1942 a fungous disease destroyed a large % of mealybugs in infested apple orchards. In the fall of 1942 the mealybug population was extremely low and it is believed that the reduction in the infestation was mainly due to the attack of the fungous disease. Environmental conditions, favorable for the development of the fungous disease of the mealybug in apple orchards, are a warm, humid atmosphere lasting for several days and a heavy infestation of the insect. The fungus seems to be similar to the Isaria stage of Cordyceps clavulata but little information is available on the identity of the fungus and apparently the name of the pathogen has not been definitely determined.