Lawn Chemicals to Kill Roundworms

Chemicals for Control

• The chemicals that are used for controlling nematodes or roundworms are referred to as nematicides. The chemicals are further identified as pre-plant, or those that are used before grass establishment; and post-plant, or those that are used when roundworm problems emerge in established lawns. The majority of the chemicals for killing roundworms are restricted-use pesticides, which require a licensed applicator and are not available to homeowners.

Pre-Planting Nematicides

• The pre-planting nematicides come in the form of soil fumigants and all are restricted-use chemicals. Recommended products include combinations of methyl bromide and chloropicrin in various concentrations, metam-sodium, dichloropropene and dazomet. The use of pre-plant nematicides suppresses nematodes population for an entire season.

Application Suggestions

• Pre-planting fumigants work best when soil temperature are between 50 and 80 degrees F in the upper 6 inches of soil. Make sure the soil is clod free and does not contain undecomposed organic material. Fumigation success is low in very wet or dry soil. Cover the treated areas with a plastic tarp for several days following chemical application for best effect.

Post-Plant Nematicides

• All post-plant nematicides except chitin come in the form of liquid or granules. Chitin is also the least toxic among all recommended post-plant roundworm control chemicals and may be used in landscapes, and commercial and recreational grass areas. Recommended chemicals include phenamiphos, ethoprop and chitin, and other organic nitrogen materials.

Application Suggestions

• Irrigate all treated areas well after application of post-plant nematicides. Apply at least ½ inch of water to prevent possible grass burn. Avoid using chemicals near water sources or where runoff is likely in order to minimize risk of contamination. Do not use the grass until the grass is completely dry. The best time to use the chemicals is during spring. In case of heavy infestation, treat grass again during late fall or early spring.