St. Gabriel Organics Milky Spore Granular Grub ControlMilky Spore is a bacterium that infects and kills grubs. You apply milky spore to your lawn and water it in so grubs become infected by swallowing a spore when feeding on grass roots. The grub is killed 7 to 21 days later. As the grub decomposes billions of new spores will be introduced into the soil from one grub. As the spores multiply in your soil, they spread to cover the entire lawn. As time passes, the spores will spread to neighboring lawns.