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.