The Best Time to Spread Grub Killer in Massachusetts

Beetle Life Cycle

• According to the University of Massachusetts-Amherst Agricultural Landscape Program, four species of grubs are particularly problematic in Massachusetts and other New England states: the European chafer, Japanese beetle, oriental beetle and Asiatic garden beetle. Adult females lay eggs in the soil in midsummer, and the grubs actively feed on grass roots during spring and from early July through the middle of autumn. Grub-killing insecticides must be used while the grubs are actively feeding to work properly and help control damaging populations.

Neonicotinoid Insecticides

• Neonicotinoid insecticides, as their name implies, are chemically related to nicotine. These pesticides are particularly effective against insects that feed on plants, especially sapsuckers. They're most often used as systemic insecticides, meaning that you treat the soil and the plants' roots absorb the chemical and transport it through the rest of the plant. Neonicotinoids include clothianidin, imidacloprid and thiamethoxam. For most of these, application is when the female beetles are laying eggs. However, egg laying can change year to year and these products don't remain active long enough to control all grub populations due to the variance in egg-laying time. The UMass Turf Program recommends applying imidacloprid-containing pesticides in mid-June and the other two active ingredients only slightly earlier based on residual activity. The Asiatic garden beetle grub is resistant to imidacloprid and has a strong tolerance for other neonicotinoids. Spread imidacloprid granules at a rate of 1.4 pounds per acre using a drop or rotary spreader. Always read the detailed application instructions on your chosen pesticide.

Chlorantraniliprole Insecticides

• Chlorantraniliprole is a different kind of insecticide and is newer than many of the classic grub-controlling insecticides. Nearly all insecticides have a signal word that relates to the product's toxicity level. These words include, from most dangerous to least: Danger, Warning and Caution. Chlorantraniliprole is so low in toxicity that it doesn't even require the word "caution" on its label. This product is highly effective against grubs and certain caterpillars, but it takes a long time -- two to three months -- for this product to break down in the soil and become effective. The UMass Turf Program recommends applying this product during spring, mid-April through early June. To use, apply this product with a spreader to dry soil and water -- approximately 1 inch of water -- to activate the granules.)

Grub Pesticide Considerations

• Neonicotinoids have come under scrutiny as research is finding they may be potentially toxic to bees due to nectar and pollen poisoning. Nearly all pesticides can have an adverse effect on nontarget organisms including bees, mammals, aquatic organisms and birds. However, applying insecticides at the correct time and using as little as possible can help protect against adverse effects.