Purpose of Nematode Management: To keep nematode population densities at a low level during the early growing season to allow cotton plants to establish healthy root systems. The goal is NOT the complete elimination of nematodes, because they are a normal part of the soil microbial population.
Steps for Developing a Nematode Management Program:
- Sample field(s) to determine if nematodes are present; if so, establish population density levels. If NO species are detected, the strategy is to make sure none are introduced.
- If nematodes are present, the strategy is to keep them from spreading to non-infested fields and to reduce population densities.
- Effective management practices require knowing which field(s) is/are infested, genera present, and population densities.
- Lance nematodes should be identified by specific species.
- Develop a Nematode Management Program well in advance of planting.
(For more information, see Nematode Soil Sampling). - Review analysis of soil samples taken last fall to identify nematode species, their locations, and their densities.
- Review nematode control options -- cultural and chemical practices -- that are available/practical in your situation.
- Design and follow a strategy that suits your special situation. Consider factors such as history of cropping patterns, soil types, single/multiple nematode species present, and weather anticipated.
Types of Nematode Management Practices:
- Use of tolerant varieties of cotton. Many early resistant cotton varieties were developed primarily to control the root-knot nematode/Fusarium wilt complex. The Acala variety has shown good resistance in western areas. Today most commercial varieties have some tolerance to this complex. Very few varieties of cotton show significant tolerance to other major cotton nematodes.
- Cultural practices:
- Tillage. If practical at the end of the growing season, root systems of plants should be turned up and exposed. This helps reduce populations of certain nematodes by exposing them to drying and temperature extremes. Subsoiling can be used in some areas to aid deeper plant root penetration.
- Water Management. Irrigation reduces crop moisture stress in fields with high nematode populations. Water should not be allowed to move from nematode infested fields to non-infested fields.
- Clean Equipment. Implements, tools, and equipment should be cleaned of soil and root debris before moving from infested to non-infested fields.
- Rotation. Rotation of a non-host crop with cotton for one or more years reduces nematode populations. Reniform nematode populations can be reduced with one-year rotations from cotton to grain sorghum, wheat-fallow, or certain soybean varieties. In North Carolina and South Carolina, sting nematodes can be reduced by rotating to watermelons or tobacco. This rotation works well in Georgia where peanut rotations can be used also. In California, crop rotation is useful for reducing root-knot nematodes to levels which do not cause damage. These crops include: cowpea, alfalfa, and processing tomato varieties with the Meloidogyne incognita gene.
- Chemical Controls:
- Fumigants. These are non-selective materials that vaporize when applied in the soil. As gases, they move up through air spaces in the soil, killing nematodes and other microorganisms. After applying most fumigants, a waiting period is required before planting.
- Non-fumigants. These are available in liquid or granular forms. They are applied either in a band or in the seed furrow at planting. These materials move down through the soil killing nematodes directly, or by interfering with feeding and reproduction.
Non-fumigants protect plants early in the growing season allowing them to produce deep, healthy root systems. Control is temporary. The availability and conditions for using these materials vary from state to state. Specific recommendations and guidelines are available from local extension agents and state specialists.
