Milky Spore

Milky Spore is a naturally occurring microscopic bacteria (Bacillus popilliae) that kills Japanese beetle grubs before they can grow into ravenous adults. It's a long-term solution because it survives winter temperatures. The Milky Spore population increases each year, reaching peak effectiveness about three years after application, and lasts ten years or more. Apply in the summer and early fall when the soil is above 65 degrees F. This is when the grubs are actively feeding, and thus the best time to attack them.