With the active ingredient Bacillus popilliae, Milky Spore Powder is a
natural treatment that kills Japanese Beetles in the larval (grub)
stage. Once grubs ingest Milky Spore, they die within 7 to 21 days and
the Bacillus popilliae spores continue to reproduce and spread
naturally to control larvae in the area for up to 20 years. A 40-ounce
canister treats 10,000 square feet and can be used any time the ground
is not frozen.