If you are after a grub preventative, don't just grab the first thing you see that says “grub killer” on it. There are grub preventatives and grub control products, and they are very different. At box stores they are typically all mixed together in the same section, which can really cause some confusion.
First, when looking for a grub preventative, always check for the right active ingredients. The two most common ingredients that prevent grubs are chlorantraniliprole and imidacloprid. These are the products that target grub larvae in the earliest stage of their life cycle before they damage your lawn.
Secondly, avoid grub products that say “contact killer”. The vast majority of “grub killer” products on the market actually are contact killers, or what we call grub control. These products target adult, active grubs in your lawn. These will NOT help you prevent grubs.
Lastly, the label can help you determine whether you have a preventative or a control. Look specifically for the application timeframe instructions. If the instructions say to apply late summer/early fall, then it is NOT a preventative. Preventatives will ALWAYS tell you to apply the product late spring to early summer.
Knowing the difference is crucial, and it is VERY easy to pick up the wrong product. Pay close attention!