The only eco-friendly grub control is Milky Spore Disease. Milky Spore is a disease that only affects white grubs. It won’t hurt earthworms or even a bird that eats a grub that has the disease. Milky spore needs to be applied two or three times a year for three years to reach “epidemic” proportions in the soil. Milky Spore is best applied in spring and fall and must get watered in heavily right after application just like the other grub controls. After that the grubs that hatch into your lawn will contract the disease then die reproducing the disease and spreading it throughout the soil. Milky Spore is more expensive up front but will last at least 20 years once it takes hold. Not a bad investment really. Over the years it will actually save you money to say nothing about the time you won’t need to spend spreading chemicals and running sprinklers.