If you’ve noticed brown, dying patches in a sunny area of your lawn, or patches of lawn that appear to have been torn up, it’s possible you have a grub infestation. Grubs are insect larvae that feed on the roots of sunny, well-watered lawns during the spring and fall months. They do considerable damage to the root system of grass, causing large, brown areas of dead grass. Untreated lawns can be killed outright from a severe grub infestation.
Grubs are the C-shaped larvae of various beetles. Fully-grown larvae are one-half to three-quarters of an inch long. Early indications of grub infestation are irregular patches of dry grass, flocking birds, or entire areas of turf being torn up by raccoons, possums and skunks looking for a tasty treat. Damage can be witnessed by tugging on the grass surface. If grubs have been eating the root system, patches of turf will pull up easily like a rug, and the soil will show grubs.
Grubs eventually turn into beetles that eventually lay eggs which turn into grubs, and the cycle repeats. If you treat for grubs when they’re smaller, while they are feeding on grass roots during late summer to early fall, they’re easier to eradicate. Annual white grub life cycles are simple, as they only have one egg-laying period per year, while Japanese Beetles have several life cycles per year. During summer, adult beetles fly around. Other species like Japanese beetles buzz about during the day, while others (like chafers) fly around at night. After these adult beetles mate, they head down into the soil to lay their eggs. Once the eggs hatch, the tiny grubs start to feed on your lawn. This is when they’re so small you often don’t see them or their damage. During September and October, grubs continue to feed and grow. In November, grubs stop feeding and burrow down 3 to 12 inches and make winter homes.
Once spring comes around, the grubs work their way up to your fresh springtime grass to feed on your turf’s tender roots. By this time the grubs have matured, so they can really do a lot of damage.
What should be done to stop these insects? We recommend a grub-specific insecticide applied as soon as damage is noticed, usually in June. We recommend following up with a second application at the appropriate time, around September. An organic approach would be to apply beneficial nematodes prior to any infestation. This is not a curative option, but can be used preventively.