Nematodes are major pests of lawns throughout the Southeastern United States. They are microscopic roundworms that live in the soil and on plant roots. Nematodes are particularly a problem in areas with warm temperatures and sandy soils.
Nematodes injure lawns by feeding on plant root cells with their needle-like mouthparts (stylets). As a result, the root system becomes damaged to where the lawn cannot properly absorb water and nutrients. Then the lawn becomes thin and weak, making it much more susceptible to other stresses, such as drought.
Nematode damage to lawns may appear very similar to symptoms caused by other stresses, so a close examination of the site and a soil test is important. An accurate diagnosis of nematode damage can be made when the following types of evidence are considered:
Above-Ground Symptoms: The lawn may appear yellow, weak, and slow to grow. Areas of the lawn may begin to thin, allowing weeds to invade easily. During periods of drought or mild stress, the lawn may wilt. Affected areas may appear irregular in size and shape since the numbers of nematodes can vary greatly within a few feet.
Below-Ground Symptoms: Grass roots that are short, stunted, or have knots and swollen areas on them may indicate a nematode problem. The root system may also appear shallow with areas that are dead or branched excessively.
Laboratory Test Results of a Soil Sample: Nematode sampling guidelines are available from any local county Extension office. There is a nominal charge for each sample to help defray the costs of operating this service. For nematode sampling and diagnosis, see Nematode Assay Lab. Samples will be analyzed to determine the types of nematodes present and their quantities so appropriate recommendations for control can be made.
Lawns Commonly Affected
All types of lawns grown in South Carolina can be affected by nematodes. However, the most damage occurs to lawns grown in the sandy, coarse-textured soils of our state. The Sandhills region of the Carolinas and the sandy portions of our coastal areas are commonly infested with the most destructive nematode, the sting nematode. Sting nematodes are generally limited to coarse-textured soils that are high in sand content. Therefore, they can cause serious damage to any type of lawn that is grown in the region.
Other parasitic nematodes include: lance, ring, root-knot, spiral, and stubby root nematodes. Individual grass species have different sensitivities to nematode pressure. For example, centipedegrass is very susceptible to damage from ring nematodes. Infested lawns typically have poor growth, become thin, and are easily invaded by weeds.
Prevention & Treatment: Once nematodes are identified as a serious problem in the lawn, several things can be done. Chemical control in the home lawn is available, but must be done by certified pesticide applicators and can become pricey due to the potential for nematodes to move vertically within a soil profile depending on season, as well as some species of nematodes existing within a plant root system, known as endoparasitic. Other methods that can reduce the effects of a nematode problem are:
- Improving the Overall Health of the Lawn: Maintaining a healthy lawn is the best way to manage nematode damage in home lawns. Irrigate the lawn weekly during periods of drought and keep fertility levels adequate. Use deep and infrequent, early morning irrigation to encourage deep root growth. Determine fertilizer and lime requirements through soil testing. Core aerate the lawn every one to two years to increase root health and rooting depth. Dethatch the lawn as needed. Finally, manage any turfgrass insect and disease problems. A healthy lawn with a root system slightly damaged by nematodes may survive if other stresses are kept to a minimum. For more information about these topics, please see:
HGIC 2360, Controlling Thatch in Lawns
- Planting a Different Kind of Grass: Selection of different turfgrass species may provide a solution to certain nematode infestations. For instance, substituting St. Augustinegrass for centipedegrass in areas heavily infested with ring nematodes has been successful in some cases. Choose a substitute grass only after careful consideration of the site and maintenance requirements of the turfgrass in question. For more information, please see: HGIC 1214, Selecting a Lawn Grass.
Excerpted from Diseases of Turfgrasses in the Southeast, EB 146.
Originally published 05/99