There are two types of chemical control products i.e., insecticides for grubs with different application times: Preventative and Curative

"Preventive" products are used to prevent future grub problems, not to control the grubs present in the lawn in the spring. They will not work on grubs found in the lawn from the middle of October through the middle of May. However, when applied in June or July they provide excellent protection against the next generation of grubs. "Preventive" products containing imidacloprid, thiamethoxam, clothianidin should be applied and irrigated into the soil in June or July.

There are two chemicals, carbaryl and trichlorfon, that are considered "curative" treatments. They are short-lived compounds that kill all life stages of grubs. These two insecticides are the only options if high numbers of grubs are found in the fall and in spring before early May. They should be applied in September-October.

It is important to read the label to determine which chemical is used in the product. The label will also tell you the best time to apply.

Following is a link to Michigan State University Extension site with more information about products to use for grub control and timing: https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

Following is a link to Penn State Extension with grub control information: https://extension.psu.edu/white-grubs-in-home-lawns

Timing for grub control application listed for Michigan and Pennsylvania are similar to Ohio. The product label will also recommend an application time.