Solutions for the Organic Control of Grub Worms in Gardens

Several natural insect control methods are used to control root-eating grubs in the garden soil.

Grubs are the larvae of various types of beetles. Most grubs are white, yellow or brown, fat and C-shaped. They feed on the roots of several types of plants, including vegetables and lawn grass. Adult beetles lay eggs in the soil. Once they hatch, the grubs begin feeding on decaying garden debris. They overwinter in the soil and begin eating the roots. They remain in the soil for up to four years before emerging to feed on aerial plant parts and lay eggs.

Native Predators

Apply parasitic nematodes in the soil to control grub infestations. Parasitic nematodes like Steinernema carpocapsae and Heterorhabditis heliothidis enter the grubs' bodies where they release an intestinal bacterium that paralyzes and kills the grubs within 48 hours. Parasitic wasps like ichneumon, trichogramma and braconid wasps kill grubs by stinging the pests and feed on their bodily fluids. Females lay eggs inside the grubs, which hatch and kill the grubs. Place birdhouses, bird feeders and bird baths near the plants to attract birds, which feed on grubs.

Maintenance

Clean up garden debris to prevent overwintering adult beetles and grubs. Throw the debris in the garbage instead of the compost so the garden pests don't continue to survive by feeding on the organic matter. Till the soil once a year to expose the pests to their natural predators.

Beauveria Bassiana

Beauveria bassiana is a biological insect control for many soil-dwelling pests, such as grubs. The fungal agent is safe to use on a wide range of plants, including vegetables, fruit trees, vines, ornamentals and lawn grass. Beauveria bassiana works as a direct contact spray. Apply the spray according to the label directions. It works best in cool, moist conditions, so keep the soil watered well. The spray also kills beneficial organisms, so use it cautiously.

Spinosad

Spinosad is an insect toxin that is derived from a type of bacterium called Saccaropolyspora spinosad. Spray the soil according to the label's directions either in the morning or afternoon. When the grubs eat the roots, they ingest the toxin and die.

Neem Oil

Neem tree seeds produce a substance called azadirachtin, which is poisonous to grubs and many other insects. Neem oil has systemic properties that cause the plant to absorb the chemicals into the tissues through its roots and leaves. The roots become unpalatable to the grubs, and if they continue to feed, they are unable to molt and lay eggs. Apply neem oil every four to seven days, depending on the infestation's severity. Reapply after heavy rains.

References

• "The Organic Gardener's Handbook of Natural Pest and Disease Control"; Fern Marshall Bradley, et al.; 2009
• "Southern Living Garden Problem Solver"; Steve Bender; 1999
• "Orthos's Home Gardener's Problem Solver"; James D. Blume; 2001