NEMATODES ON TURF GRASS Various nematode species   F A C T S H E E T

Introduction

Living in the cold Northeastern United States, we are fortunate to have fewer plant parasitic nematode problems than those living farther south. There are approximately twelve different species of plant parasitic nematodes that cause problems on various turfgrass species. Plant parasitic nematodes cause major problems on warm season grasses, but cool season grasses can also have substanial decline and damage symptoms. Nematode feeding can open sites for other pathogens which can cause more severe damage.

Symptoms

Above ground symptoms of nematode damage include chlorosis, wilting, and reduced growth. Symptoms are often found in a random patchy pattern. These become more apparent when the turf is stressed by high temperatures, a lack of moisture or poor soil fertility.

Figure 1: Root knot nematodes symptoms of galling (provided by Dr. Eric B. Nelson, Cornell University) Figure 2: Vermiform plant parasitic nematodes within root tissue (provided by Dr. Eric B. Nelson, Cornell University)

Below ground, symptoms may include galled roots, the presence of cyst bodies, and/or a poor, declining, discolored root system. Root symptoms vary widely. Some species of nematodes cause tissues on which they feed to grow strangely, some stop the growth of the roots, and others kill the cells on which they feed leaving patches of dead tissue as they move on.

Feeding sites are ideal locations for entry of fungal plant pathogens and diseases caused by these organisms are often found in conjunction with high nematode populations. Fungi and bacteria which cause root rots, wilt, and other plant diseases often infect nematode-damaged roots earlier and more severely than uninjured roots. Some viruses can also be transmitted by nematodes. Laboratory analysis on soil samples is the only way to detect the kinds of nematodes associated with a problem. These analyses may be necessary to identify the most effective control measures.

Disease Cycle

Nematodes are microscopic, worm-like, animals with life cycles that include one egg stage, four juvenile stages and one adult stage. Nematodes overwinter using a number of strategies in egg phase, within the dead female body, or in plant material. As the weather warms in the spring, the nematodes become active and begin feeding. Females of some species become enlarged when mature. They either produce and then deposit a mass of eggs outside of their bodies--as do female Root Knot nematodes, or they house the eggs within their bodies--as do female Cyst nematodes.

Management Strategies

The best control method is keeping the plants as healthy as possible through proper fertilization and reduction of stress. In some situations, nematicides may be useful, but most are highly toxic, so careful consideration should be made prior to making a decision to use any of these products. The nematicide Nemacur 10% Turf fungicide is still registered for use on golf course fairways in New York State, but it is restricted use and may only be used on mature plantings of labelled grass species. Products such as Basamid Granular will kill nematodes and plants and can only be used prior to golf course construction or when renovating turf. Use of these toxic materials can be harmful to other beneficial organisms present in the turf ecosystem. There are no known resistant varieties of turfgrass.

Updated, SLJ, 1/05