Hi Erica-

Thank you for sending your question to Ask Extension.

I have attached a couple articles that talk about grubs, and how to control them in your lawn. Each one begins with you making sure that the number of grubs affecting your lawn is a significant enough to create a, “Wow! I need to treat this problem” moment. Healthy lawns can sustain a population of 5 or fewer white grubs per square foot. To determine the number per square foot, dig up a square 2+ inches deep near an area that appears to be affected. Roll the sod back, and count the number of grubs that you see in the square foot.

If your number per square foot is greater that 5, you may consider one of the following non-toxic treatments.

• Milky spore disease—the spores are applied to the lawn, after eating the spores
• the grubs die and release the spores into your lawn. This may take a season or two to notice the benefits
• Beneficial nematodes
• Neem oil

It is best to treat in late summer or early fall to kill young, feeding grubs while they are close to the surface. Follow the package directions for successful treatment. All three treatments can be found from online distributors.

You may be seeing damage from the fall and winter feeding of the grubs that have over wintered in your lawn. In June and July, the beetles will emerge looking for food and mate. In July they will lay eggs, and the first eggs will hatch in 2 weeks. In August through October, they will continue eating the roots of your grass and you may find brown patches. In spots where you see the damage, replant, water well and take steps to create a healthy turf.

A soil test, which you should perform every two or three years, is also a good place to start when thinking about creating a healthy turf (homesoiltest.msu.edu). It will tell you the pH of your soil, organic material present, and any fertilization needs. I have also attached a tip sheet on good practices for a healthy lawn—mow your lawn to a height of 3-4”, fertilize appropriately (according to the soil test), and water properly. These are all good steps to follow in deterring grubs from finding your lawn an attractive place to stay.

https://www.psu.edu/news/fayette/story/take-control-grubs-your-lawn

https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

https://www.canr.msu.edu/resources/go_green_lawncare_tip_sheet