Insects That Eat Shrubs & Grass Roots

Root-feeding insects are typically most abundant in the top 5 inches of the soil.

Identifying and controlling root- and shrub-feeding insects involves narrowing down possibilities by identifying feeding sites like roots, leaves and stems. Once identified, prewatering, applying insecticide treatment, mowing and delaying watering after treatment are key to long-term control. Typically, spray insecticides are more effective than products that come in granular form. Insecticide should also be applied to plants when they're dry.

Two-Spotted Spider Mite

The two-spotted spider mite (Tetranychus urticae) lives in dead leaves or under bark of shrubs and trees during the winter. The mite thrives on herbaceous plants like azalea and rhododendrons. The mites may be mistaken for other types of beneficial mites that appear around the same time. The spider mite, however, is green-yellow or green with two dark spots on its back. It also moves slowly and leaves a green mark if crushed. Mites beneficial to your shrubs move quickly and leave a reddish mark. Shrubs should be treated only if beneficial mites aren't present.

White Grubs

Grubs are Japanese beetle (Junebug) larvae. They live and feed on grass roots during the summer months. Their bodies are typically c-shaped and cream or white. Turf affected by white grubs tends to turn brown and lift up easily or even roll up if the infestation has completely destroyed grass roots. Once mature, the bugs come up from the soil and eat fruit, leaves and flowers. Eggs are laid beneath turf soil and hatched in late fall. Grubs burrow deep into the soil for winter months and resume feeding when weather warms. Lawns can be treated with neem oil or insecticides.

Ground Pearl Scales

Pearl scale larvae, or Homoptera, have hard shells that look like small pearls, hence their name. The insects are harder to see than grubs, since they are 1/8 inch long, no larger than a pin head. They live under grass soil. Ground pearl scales deplete grasses of fluids, especially species like Bermuda grass. Infested grass turns yellow or brown in the summer then will die a patch at a time. Sod should be carefully inspected before laying it in your lawn, as pearl scales are difficult to get rid of. Garden and lawn equipment should also be cleaned between uses to minimize the chance of infestation.

Phoenix Billbug

Like white grubs, billbug larvae live below the ground and feed on grass roots. Unlike white grubs, however, billbug larvae do not lay eggs. Larvae have a distinct humped-back shape. Adults -- referred to as weevils -- can be identified by their bill-shaped snout. You may also notice small holes in your grass. The area around the hole sometimes turns yellow so that grass is specked. Introducing nematodes, rotatone or milky spore disease can prove effective control methods, as can insecticide labeled for billbugs.

References

• Arizona Cooperative Extension: Entomology: Insect Pests
• University of Illinois Extension: Diseases and Insects of Shrubs and Small Trees
• New Mexico State University Cooperative Extension: Billbugs

Resources

• North Carolina State University: Lawn/Turf Pests
• University of Illinois: Shrub Pests