Milky Spore uses the naturally occurring bacterium, Paenibacillus popilliae. This bacillus primarily targets Japanese Beetle grubs, the soil-dwelling larval stage, before they become the destructive adults. These grubs target lawn and garden soil, causing unsightly damage to turf and crop loss where they are active. Once applied, Milky Spore must be ingested by the grubs as they feed. The more spores that are in the area, the greater the chance of infection. Once ingested, Milky Spore kills grubs within approximately 3 weeks and continues to propagate while Japanese Beetle grubs are active.