Apply grub killer before and during the time new grubs hatch, in most areas, between June and August. Grubs are the larval form of beetles. Look for beetle activity. Grub killers are effective only before grubs are large enough to damage your lawn. It is too late after you notice their damage.
About this Author
Lee Roberts has written professionally in different capacities throughout her career. She has written for not-for-profit and commercial entities since she received her B.A in sociology from the University of Michigan in 1986. She has been published on eHow.com. She is currently writing an extensive work of fiction.