Controlling Grubs in Lawns in California

Treatment Threshold

• With strong mouthparts, grubs congregate at the grass root level as they eat the nutritious plant material. Most lawns sustain some grub damage, but more than five grubs within a square foot area often causes significant damage. Turf may be pulled off of the soil, much like rolling a rug off of the floor, if roots are fully decimated from grub feeding. Summer into autumn is the prime time for grub infestations as the larvae grow large enough to hibernate and pupate until next spring. Brown dead spots across your lawn are a calling card of high grub populations.

Proper Watering

• In general, water your lawn infrequently and deeply to an 8-inch depth. Deep watering encourages vertical root growth for a healthy and strong lawn that a small grub infestation will not significantly damage. This irrigation strategy also contributes to healthy thatch, or decomposing stem and foliage, above the roots. If you lightly sprinkle the grass, roots remain shallow and vulnerable to grub feeding habits. Adjust your sprinklers periodically to encourage uniform coverage across the lawn. Turf interspersed with waterlogged areas and drought conditions also causes continual stress, allowing grubs to take advantage of struggling roots.

Thatch and Aeration

• Allowing moisture and air to move easily into the soil provides another barrier to grub infestation and reproduction. Healthy lawns regrow quickly to replace grub-damaged areas. Thatch often becomes thick over time with improper watering and maintenance; oxygen and water supplies within the soil disappear as particles compact and hinder root growth. Aerate your California lawn with a hollow-tine aerator. These machines pull 1- to 2-inch-long soil cores from the ground. These new soil spaces allow water and oxygen to permeate the ground along with encouraging microorganisms, like earthworms, to populate the area for natural aeration and soil turnover.

Nematodes

• If you want to eradicate yearly grub infestations without harmful pesticides, you can apply nematodes, which actually infect adult beetles before they can lay eggs. These tiny worms are applied to the lawn with water, much like fertilizing, during the late spring. As adult beetles become active in the warm weather, nematodes effectively kill them off. Nematodes, however, rely on ample soil moisture for movement and vitality. Choose Heterorhabditis bacteriophora or Steinernema glaseri nematode species to control your grubs. Other nematode species are not as effective to remove beetle larvae.