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How to Control Grubs in the Lawn
by Paul Dohrman
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Overview
Grubs live in soil and eat lawn roots. The resulting browning of the lawn occurs in late summer to early fall. This varies with the part of the country you reside, as does the best time to spray. The brown patches peel away from the soil easily, like carpet. Five or more grubs per six-inch by six-inch plot warrants treatment.
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Step 1
Apply Merit or Mach-2 insecticides broadly in the spring and early summer before eggs are laid in mid-summer, as a preventative measure. This broad treatment is in contrast to fall treatment, which is restricted to affected areas.
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Step 2
Water the lawn after application of the insecticide, about ¼ to ½ inch deep, to send the insecticide to the roots where the grubs eat. Do this both in the spring and fall.
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Step 3
Take a few samples of the lawn in August or early September. A dozen samples may be needed, since white grubs generally do not affect whole lawns. Any areas with more than three grubs in the plot should be treated. Examine a plot using a spade to cut out a six-inch by six-inch area and lifting it out to examine its roots.
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Step 4
Identify the grub species for specificity of insecticide to use. Agricultural extension personnel can do it for you, or you can do it using the Ohio State link in the Resources section below. See the University of Rhode Island link below for a match-up between species and insecticide.
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Step 5
Emphasize treatment in late summer and early fall when the grubs are still small and close to the surface. (In the spring, they are no longer feeding, and do not ingest the insecticide.) Dylox insecticide is useful for fall treatment.
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Step 6
Consider a natural approach, using neem oil. Mix it with water (as directed on the label) and spray it on affected areas in the late summer and fall.
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Step 7
Consider a biological control, using nematodes or milky spore. Both are environmentally safe. Nematodes are sprayed on, preferably when the temperature is around 70 degrees Fahrenheit. Density of spraying depends on the species of nematode. Milky spore is not effective when population concentrations are high. Research on the effectiveness of both of these give erratic results.
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Step 8
Promote shade by planting trees and growing the lawn higher, since grubs do not do well in the shade.
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- Merit or Mach-2 insecticides
Dylox insecticide
Water
neem oil
nematodes or milky spore
- Merit or Mach-2 insecticides
- Dylox insecticide
- Water
- neem oil
- nematodes or milky spore
