Between everything else you have to get done, you don’t want to hear the kids run in yelling about icky bugs. Busy moms want healthy, happy lawns their children can play on, and white grubs do not contribute to that ideal. Because white grubs, the larval stage of several types of adult scarab beetle, eat grass roots and cause sod to become spongy and roll back, they destroy turf and can cause considerable damage. If you need to resort to pesticides, do so in summer when it will be most effective.
Grub Life Cycle
In New England, white grubs are most likely the offspring of four types of beetle. The adult females lay eggs between late June and late July; the eggs hatch and larva eat plant roots from July through fall. They also emerge again in springtime, when they again feed on roots. Grubs pupate between May and July before emerging in the adult stage, at which time they start a new generation.
White grubs respond best to preventative treatment. When you apply grub killer depends on the type you decide to use. Neonicotinoids, for instance, must be applied when females are laying eggs, usually between mid-June and early August, although you should update the timing, depending on your own observations. Low-toxicity chlorantraniliprole, on the other hand, needs 60 to 90 days to become effective, so must be applied between April and June. Although preventative measures are more effective, in some cases you might need to use curative pesticides, which are usually applied in late summer.
Exact application amount and timing depends on the instructions of the particular grub killer you decide to use. For a .33G granule formulation of a preventative neonicotinoid such as thiamethoxam, for example, you would apply between 1.4 and 1.8 pounds per 1,000 square feet. When applying curative pesticides like trichlorfon, refer to the package directions for specific instructions. Usually, however, you won’t use more than about .15 pounds of trichlorfon per 1,000 square feet.
Pesticide Application Safety
Always read the label before applying a pesticide. If a pesticide is available in granular form, you’ll need a rotary spreader, or you can apply by hand, using gloves if the area is small enough. For wettable agents, you usually must dilute either a powder or a solution in water and then spray on the area. Do not store leftover pesticides or dump them down the drain or in waterways; instead take them to a hazardous waste disposal site. Wash everything you were wearing after you’re done applying. Read the label to see if you should water in the pesticide after applying, and do not apply when it is windy or extremely hot or cold. Keep children and pets away from the area while applying and until the label indicates it is safe.