Milky spore is a naturally occurring soil bacterium that specifically targets Japanese beetle grubs. Once established, it persists in the soil for 15-20 years, providing long-term grub suppression without repeated application. It's the ultimate set-it-and-forget-it biological control.
Japanese beetle grubs (Popillia japonica) ONLY. Does NOT control other grub species (June bugs, chafers, masked chafers). This is extremely species-specific. If your grub problem is not Japanese beetles, use beneficial nematodes instead.
St. Gabriel Organics Milky Spore Powder, Milky Spore Granular (Gabriel), Gabriel Milky Spore Lawn Spreader Mix. Limited product selection because only one company has scaled production.
Completely non-toxic to humans, pets, wildlife, earthworms, beneficial insects, and all plants. Cannot affect anything except Japanese beetle grubs. USDA/EPA exempt from registration requirements. OMRI organic approved.
Application: Apply in fall when grubs are actively feeding (September-October in most areas). Place 1 teaspoon of powder every 4 feet in a grid pattern. Water in lightly. Takes 2-3 years to fully establish throughout the lawn.
Patience required: Unlike chemical grub treatments, milky spore takes 1-3 years to build up enough in the soil to provide effective control. But once established, it lasts decades. Plan accordingly.
Temperature requirement: Soil temperature must be above 65°F for spores to activate. This is why fall application works well — grubs are feeding and soil is still warm.
Combine with nematodes: For immediate grub relief while milky spore establishes, apply beneficial nematodes (Heterorhabditis) in the same season. Nematodes provide fast knockdown; milky spore provides long-term control.