Do Lawn Grubs Die in the Winter?
Japanese beetles start the life cycle of white grub larva, which will emerge as Japanese beetles. During the summer, winter and spring, the grubs feed and survive in the soil, damaging crops and lawns.
Japanese beetles lay as many as 60 eggs in the lawn in May or early July. Within 50 days, the eggs hatch into larva, which are called white grubs. The white grub burrows underneath the soil and starts to feed on the grass roots.
As the temperatures start to drop, the white grub burrows farther underground. During the winter, the grubs are below the frost line and protected from the cold.
As the air temperatures start to rise and the soil temperatures warm, the grubs migrate back to the surface, where they once again start to feed on the root systems of lawns and crops.
This summer, winter and spring cycle will continue for two to three years before the white grubs emerge from the soil as Japanese beetles and start a new cycle by laying eggs on the ground.
Effects Of Grubs In A Lawn
A heavy infestation of scarab beetle grubs, also called white grubs, causes irregular patches of dead grass in the lawn. Walking on a lawn damaged by white grubs, feels spongy. Root damage also differs; billbug grubs feed on the upper parts of grass roots. Armyworms and cutworms are not technically grubs, but they are larvae that live in the soil of lawns and cause damage that resembles that of grubs. A low number of grubs in a healthy lawn is harmless. Treatment is warranted when there is visible damage and the grub concentration reaches a critical limit. One billbug grub per square foot of lawn is considered sufficient for starting treatment. Fight grub infestations with cultural methods, biological controls or chemical insecticides.
- North Dakota State University: White Grub Management for North Dakota
- University of Nebraska-Lincoln: Turfgrass Entomology
- Utah State University Extension: White Grubs
- UC Davis IPM Online: Masked Chafer (White Grubs) - Cyclocephala spp.
- UC Davis IPM Online: Black Turfgrass Ataenius
- UC Davis IPM Online: Billbugs
- Utah State University Extension: Armyworms and Cutworms in Turfgrass