First we strongly recommend following the techniques in the section here on Control Grubs Using No Insecticides. We also strongly recommen you NOT use Japanese beetle traps. They ultimately increase your beetle population rather than lower it.
Since we no longer recommend any fast acting synthetic grub control products your natural and organic options need to be viewed in the long term - 3 to 4 years for complete grub control. We recommend a two step program. In the first year, in September, we suggest you apply beneficial nematodes to your lawn. In September the grubs have hatched from the eggs and are close to the surface of the soil. A week later we suggest you apply Milky Spore disease powder as directed by the label. If you do this two years in a row, in the third year you should see little or no sign of any grub damage to your turf and that situation will last for up to 20 years because the Milky Spore lasts that long.
In September Control With Predatory Nematodes
Achieve effective control of grubs by spraying an insecticide product containing predatory nematodes. These microscopic worms are packaged as a powder or in a gel and are activated by adding water. Spray the liquid slurry on infested turf or soil in the late afternoon or early evening as directed on the product label. The beneficial nematodes travel on a thin film of water through the soil and find their way to the grubs. When they burrow inside them to lay their eggs, they also transmit bacteria, which kill the grubs. This will, reduce a population of grubs by up to 80 percent within about 4 weeks. However, conditions in the soil, the age of the nematodes, and the effectiveness of the application may delay this result somewhat. Read label instructions. It costs roughly $10 to treat 1000 square feet of lawn with predatory nematodes. Because they are relatively expensive, they are most suitable for small areas.
In September Start Milky Spore Disease Program
Optional In September Control Grubs By Spiking
White grubs feed nearest the surface of the soil in late spring and again in August and September. That is the time when you can kill many of them with some form of spiking tool that has sharp tines at least 2 inches long. Golf shoes do not do the job, but special shoes with spikes attached to the bottom are now available. You can also purchase a hand spiking tool that does a good job. The more spike holes in the turf the more grubs killed and the better your soil. Research shows that turf that is spiked frequently contains about half as many live grubs, and grows stronger plant root systems because the spiking aerates the soil. In planting beds, prior to planting dig into the soil a few inches and turn over shovelsful to surface grubs for birds to eat.