Developed by the USDA, Milky Spore is a natural all season grub control. Use spring, summer and fall for two seasons. Once established in your lawn, Milky Spore will remain viable for 15 to 20 years. It begins working immediately as soon as it is applied when grubs are feeding. Once all of the grubs are destroyed, the spore will remain dormant but viable in the soil until new grubs come along even years later. Will not harm beneficial insects, animals, pets or man. Safe for use around wells, ponds, and streams. Harmless to birds, bees and fish.