Turfgrass Disease Information Note 2 (TGIN-002)
Henry C. Wetzel III, Extension Plant Pathologist
Nematode damage can be severe in some lawns in southeastern and southcentral North Carolina where soils are very sandy. Turf affected by nematodes usually appears weak and thin. It may have symptoms of nutrient deficiencies or wilts rapidly during dry weather. Similar symptoms may be caused by other problems such as poor fertility, lack of moisture and some diseases. Root stunting, excessive branching and even death of roots may occur with some nematodes. These symptoms are not usually adequate to identify nematodes as the major problem, therefore, soil samples must be assayed for nematodes. Also, a soil fertility test is recommended to eliminate nutritional problems as a major factor.
Nematodes are small eel-like worms that are too small to be seen without a microscope. Nematodes that attack plants have small needle-like stylets which are used to puncture plant cells to obtain nutrients. Different nematode species that attack turfgrasses cause root stunting, death of roots, knots on roots and some cause no apparent harm even at high numbers. Nematodes usually do not kill the host plants, but they do increase damage from other stresses, such as drought. Ground pearls (soil insects) cause serious damage in sandy soils on centipedegrass that can resemble nematode injury. If this insect is present, some of the suggestions for reducing nematode damage may be useful.
Nematodes that are found most frequently in soil from turfgrasses are ring, stunt, spiral, lance, stubby-root and sting. Only the sting and the stubby-root nematodes have been shown to cause severe damage on turfgrasses in research projects at North Carolina State University. The sting nematode is known to be the most damaging nematode and frequently occurs in the sandy soils of eastern and southcentral North Carolina. It is difficult to grow good quality turfgrasses where this nematode is present.
Nematicides are not currently labelled for the control of nematodes on turfgrasses in home lawns. Good turf management practices must be used in place of nematicides in home lawns to grow healthy turfgrasses that can tolerate some nematode damage. Some organic soil amendments, such as shrimp and crab shells, may encourage fungi that kill nematodes. Incorporation of organic matter in the soil before planting will help the soil increase antagonistic microorganisms and help grow healthier turfgrasses. High rates of organic matter should be used carefully on centipedegrass because too much nitrogen may be released and cause excessive growth that would result in decreased drought and cold tolerance.
Some management practices can be used to help minimize the damage from nematodes. The use of good fertilization programs to insure proper levels of nutrients, irrigation to supply adequate soil moisture, and recommended cutting heights will help turfgrasses tolerate certain levels of damaging nematodes. In some cases an alternative turfgrass may be considered. For example, centipedegrass is more susceptible to the sting nematode than bermudagrass or bahiagrass . Therefore, bermudagrass would be the best choice for use in residential lawns where high quality turf is desired if irrigation is available. Zoysiagrass has been observed to be very sensitive to damage from sting nematodes and would not be a good replacement for centipedegrass in sting nematode infested soil. Bahiagrass may be the best choice for lower quality lawns and in large commercial lawns in eastern North Carolina. Very little damage from nematodes has been observed on this course textured grass.
Nematode management practices must be incorporated into lawn management systems where nematode damage occurs. This approach will offer new challenges to turf managers and homeowners since chemicals are no longer available to control nematodes in residential lawns.
Published by North Carolina Cooperative Extension Service Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Reformatted Feb. '00 by Plant Disease and Insect Clinic