If you plan on using a grub preventative on your lawn, the first half of July is a good target date. Preventatives are normally used on areas that have had a history of grub problems. Traditional grub insecticides such as Dylox are normally applied in late July after grubs are present or as a rescue treatment once damage is seen. Products that contain Merit (imidacloprid) or Mach 2 (halofenozide) are considered grub preventers.
Actually, neither product prevents grubs, but rather they kill grubs when they are quite small, and long before they cause damage.
Merit and Mach 2 are safer to use around pets and humans than traditional grub killers. Merit can be found in Bayer's Season-Long Grub Control and Grub-Ex. Mach 2 is the active ingredient in Kill-a-Grub.
Remember all grub products must be watered in before they are activated.
— Scott Eckert is a Kansas State Research and Extension Agent for Harvey County. Horticulture is his specialty.