Hi Pam- Thank you for sending your question to AskExtension!

Even though you have experienced grub damage for years, I would want to make sure that they are currently the problem in your lawn. Identifying the grub, and formulating a plan that may take time to be effective, is crucial.

In mid-May, the grubs begin feeding after they hatch, causing damage to roots in September and October. They are fully grown in late October, and over winter as large grubs. They resume eating in spring, so damage can appear in your lawn from March to May (from the previous season feeding), and then again from September to November (from spring feeding). This is why you may need to anticipate a multi-year plan as a cure.

In determining if grubs are a problem, dig up a few square foot patches of turf around a damaged area. Dig 2” deep, and roll up the sod. The grubs should be just below the turf. A significant number per square foot would be 12 or more. If this is the number that you find, you will want to treat with a preventative. Look for the active ingredient on the product packaging. Preventatives containing imidacloprid, thiamethoxam, clothianidin or chlorantraniloprole, as the active ingredient, will not kill grubs in the spring, but when applied in late June/July it will protect against next years grubs. You will want to treat 1-2 years in a row, continuing to check soil patches each year for declining grub numbers. If you choose to use a product with imidacloprid, thiamethoxam, or clothianidin, mow your lawn to remove the flowering parts before applying. These chemicals are toxic to bees.

Always read and follow label directions! The label is the law!! It will give you application amounts, directions on usage and safety instructions.

Plan on watering immediately after applying, to a depth of 0.5 inches, for these chemicals to be most effective.

Healthy lawns can sustain a grub population of 5 or fewer per square foot of turf. So, along with determining if you currently have grubs, which grub is at work and how to rid your lawn of them--working to make your lawn healthier at the same time should be part of the mission. Best practices for healthy lawns include:

• Mowing at a height of 3-4”
• Proper fertilization, following the advice of a soil test(homesoiltest.msu.edu)
• Proper irrigation

I have attached a few articles on grub control, lawncare and lawn repair.

Hope this helps.

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

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