Joey from Johnston, Ri writes
Milky Spore Powder can be applied any time the ground is not frozen since it will need to be watered in, but you generally get the best results applying April through November. You may get faster control with Milky Spore when applying in the Spring and late Summer, when grubs are actively feeding. Keep in mind that complete grub control may take 3-4 years.
Answer last updated on: 03/29/2016