Type A (Bacillus popilliae) and Type B (B. lentimorbus) vars. of milky disease can be individually induced in Japanese beetle larvae by injn. into the body cavity of the respective bacterial spores. If a mixt. of the 2 spores is injd. into a host larva,only Type A or Type B develops[long dash]not both. The relative spore dosage determines which type is successful. Time is also a factor. In direct competition B. popilliae seems more potent than B. lentimorbus.