I Have Soft Spots in My Lawn

All turfgrass species are prone to disorders resulting from pathogenic infections, pest infestations or poor cultural management. Correct identification of the problem is the key to effective management. A common lawn pest creates soft areas in grass.

Identification

Lawns are susceptible to infestation by white grubs, the larva of scarab beetles. The problem is more common in sandy, light soils. White grubs are distinctly C-shape worms with white bodies and a brown head. The pests have three pairs of legs.

Damage

White grubs are root eaters and feed on grass roots. Affected grass areas start to yellow, thin and die. This creates spongy, soft patches on lawns. The resulting dead, brown, irregular areas gradually increase in size as grass is unable to utilize water and nutrients. Heavy infestation often causes grass to roll up like a rug.

Management

Introduce natural predators like ground beetles and parasitoids in infested turf. Insect parasitic nematodes are also helpful in white grub control. You can also use curative insecticides like trichlorfon. Apply insecticide when grub presence is established.

References

• North Dakota State University Extension: Lawn Diseases
• North Dakota State University Extension: White Grub Management for North Dakota
• University of Florida Extension: White Grub Management in Turf