How to Kill Soil Pests

Release nematodes into the soil to kill grubs, the larvae of beetles that chew plant roots. Nematodes are generally mixed with water and sprayed on the soil, but read label directions for specific instructions. The microscopic roundworms seek out soil-damaging pests, enter their bodies and kill large populations within 48 hours. Ideally, 3 to 6 gallons of nematode spray is effective for 1,000 square feet of soil.

Inspect the soil at night for cutworms -- tiny brown caterpillars that feed on the stems of seedlings at soil level. Cutworms usually damage plants at night, so use a flashlight and a trowel to loosen the top 4 to 6 inches of soil until you spot the 1/2- to 1-inch-long worms covered with bristles. Depending on personal preference, spray bacillus thuringiensis according to label directions, or drown the pests in a bowl of soapy water using tweezers.

Locate soil mounds in your garden or yard from where fire ants emerge and chew germinating seeds. Pour boiling water from a long, spouted kettle over the mounds to kill the damaging soil pests. Douse the mound completely with water and let it soak below to kill the pests.

Drench the soil with Bacillus thuringiensis var. israelensis to kill the larvae of gnats in soil. Alternatively, spread granules over the soil and douse with water to release the chemicals.

Bury a medium to large carrot every 30 to 36 inches in the soil to attract and catch wireworm larvae. Pull the carrot out of the soil every two to three days and dispose it in a garbage bag, along with the larvae attached to it.

Apply a chemical insecticide to control severe soil pest infestations. For effective control, use the formulation at the time of year when the particular soil pests are closest to the soil level and therefore most susceptible to the treatment. Follow label directions for applying the insecticide and water the soil thoroughly afterward to release chemicals. Avoid overwatering the area, but add enough water to ensure the soil is moist, not soggy.

Solarize the soil in the summer to kill soil pests and weeds. Mow the vegetation as close to the ground as possible and water the soil to a depth of 6 inches. Spread a plastic sheet over the ground and place bricks along its edges to keep it in place. The sheet traps the heat of the sun, killing soil pests. Remove the sheet after eight to 10 weeks.