How seed-applied nematicides work

Updated in 2026, this version replaces the 2020 How seed-applied nematicides work.

Nematicides are an important part of an integrated pest management system to control plant-parasitic nematodes. Over the past 15 years, seed-applied nematicides have increased in popularity, becoming one of the most used nematicide-application methods in row-crop agriculture, in part because they are easy to apply and fit well with existing planting practices. Seed-applied nematicides can be divided into two groups: chemicals and biopesticides (see Biopesticides for Crop Disease Management web book for more information). Some examples of chemical nematicides include Avicta (abamectin), ILEVO (fluopyram), and Victrato (cyclobutrifluram). In contrast, examples of biopesticides are Aveo EZ Nematicide (Bacillus amyloliquefaciens), BioST Nematicide 100 (Burkholderia rinojensis), and Atroforce (Trichoderma atroviride).  Most of the chemical nematicides are synthetic formulations, whereas most biopesticides consist of living spores from bacteria or fungi that multiply in the soil as seedlings develop. This article will focus on chemical seed-applied nematicides and explain how they protect the expanding root system, and factors that can contribute to their field efficacy.

How they work

Seed-applied nematicides are convenient to use for farmers and work in a way that creates a “zone of protection” around the developing root system. Nematicides move from the seed coat to the surrounding soil and water to create this “zone”, which will vary in size based on several factors, these factors are described below.  It is important to note that seed-applied nematicides will not provide complete or season-long protection of the expanded root system.

Factors that influence root protection by nematicides

Movement in root: Though the concentration of nematicide applied to the seed coat is sufficient to kill nematodes, the amount that comes off the seed coat shortly after planting is only a portion of that applied to the seed coat. Seed-applied nematicides do not move through the vascular system toward the growing point of the root system, so the amount that comes off the individual seed must come directly into contact with plant-parasitic nematodes in the soil to cause paralysis, which impedes root infection. While paralysis caused by some nematicides is irreversible, the effects are reversible with others, allowing nematodes to recover in motility and infect a nearby root once the chemical wears off or is washed away. Nematicides that bind to the seed coat are less likely to move into the soil water phase, thus limiting the “zone of protection” surrounding the roots. 

Movement in soil: There are three main factors that affect nematicide movement in the soil: solubility in water (maximum amount of a nematicide that dissolves in water), soil mobility (i.e., binding to soil particles), and water infiltration (downward movement of water). Nematicides that have low water solubility (e.g., abamectin) are less likely to be distributed in the soil water phase than those with a moderate solubility (e.g., fluopyram). Nematicides that have limited movement in the soil water phase, due to low water-solubility, have a smaller “zone of protection” with less protection further away from the seed. 

Once in the soil water phase, nematicides come into contact with soil particles. Nematicides bound to soil particles are ineffective at inhibiting nematode infection. In general, chemical nematicides move more readily in coarse-textured soils than fine-textured soils, assuming adequate water infiltration. As a result, chemical nematicides often have a larger zone of root protection in coarse-textured soils than in fine-textured soils such as silts and clays. Moreover, the zone of protection is more vertical like a “chimney” to protect the developing taproot rather than horizontal to protect lateral roots.  Therefore, seed-applied nematicides typically work better in strongly tap-rooted crops such as cotton and soybean compared to fibrous root systems like corn.   

Water infiltration is key to moving water in the soil water phase and downward throughout the expanding root system. Because water is quickly displaced in coarse-textured soils compared to fine-textured soils, the downward distribution of nematicides is often reduced in fine-textured soils, which limits the zone of protection. When using a seed-applied nematicide, water as irrigation or rainfall is needed shortly after planting to distribute the nematicide that washes off the seed coat and into the soil. This will result in a timely establishment of the “zone of protection”. 

Nematode population density: Another factor that affects root protection from seed-applied nematicides is nematode population density. Seed-applied nematicides are marketed for use when nematode population densities are low to moderate. When nematode densities are high, this usually means that there are more nematodes outside the zone of root protection, but still within the zone of root expansion. Under these conditions, the risk of nematode infection will remain high, as roots will expand beyond the nematicide “zone of protection”. 

Other variables: Other factors, such as microbial degradation and chemical half-life, play a role in the longevity of nematicides present in agricultural soils, but have little impact shortly after planting on seedling root protection. Though nematicides vary in toxicity to specific species of plant-parasitic nematodes, variability in field efficacy is more often associated with factors that limit nematicide movement from seed and within soils. 

Applying these concepts

Seed-applied nematicides can be effective in protecting seedling root development when nematode population densities are low, particularly in coarse-textured soils where irrigation or rainfall promotes nematicide movement. Soil sampling helps determine nematode population densities and track changes over time. Because seed-applied nematicides do not provide season-long protection, an integrated pest management approach may include combining a seed treatment with at least a moderately resistant variety. 

Acknowledgements

Authors

Travis Faske, University of Arkansas, John Mueller, Clemson University, Horacio Lopez-Nicora, The Ohio State University.

Reviewers

Martin Chilvers, Michigan State University, Daren Mueller, Iowa State University, Damon Smith, University of Wisconsin-Madison.

Sponsors

The authors thank The United Soybean Board, Cotton Incorporated, and United States Department of Agriculture - National Institute of Food and Agriculture for their support.

How to cite: Faske, T., Mueller, J., Lopez-Nicora, H. 2026. How seed-applied nematicides work. Crop Protection Network. CPN-4006 (Revision). doi.org/10.31274/cpn-20200519-1.