Cover crops are frequently used for various purposes, including preventing soil erosion, maintaining soil health, and suppressing weeds, pests, and other pathogens. In addition to these uses, cover crops can also play important roles in controlling soybean cyst nematodes (SCN) by reducing their populations in the soil using various mechanisms.

In this article, I highlight 5 nonhost cover crops that can be used to control SCN and identify their modes of action.

1. Alfalfa

Alfalfa (Medicago sativa) is a non-host for SCN, and planting it as a cover crop can reduce the nematode populations in the soil. The allelochemicals produced by alfalfa can suppress SCN larvae in the soil.

Alfalfa can be an effective tool in managing SCN populations. When alfalfa is grown in rotation with soybean crops, it can help to reduce SCN populations in the soil. Alfalfa is a non-host crop for SCN, which means that it does not support the nematode’s reproduction.

In addition, alfalfa roots exude compounds that can inhibit SCN reproduction and development. For example, alfalfa root exudates can contain saponins and other secondary metabolites that can reduce SCN egg hatching and limit nematode mobility.

Furthermore, when alfalfa is used as a cover crop or hay crop, it can help to improve soil health and fertility. Alfalfa is known for its deep root system, which can help to break up soil compaction and improve soil structure. Additionally, alfalfa can fix atmospheric nitrogen and add organic matter to the soil, which can improve nutrient availability and support the growth of subsequent soybean crops.

In summary, alfalfa can be a useful component of an integrated pest management (IPM) strategy for managing SCN. Alfalfa can reduce the nematode population in the soil by acting as a non-host crop and producing nematode-inhibiting root exudates. It can also improve soil health and fertility, which can benefit subsequent soybean crops.

2. Cereal rye

Cereal rye (Secale cereale) is a non-host for SCN and its deep root system can help reduce SCN populations in the soil by improving soil structure and reducing soil compaction.

Cereal rye can be an effective cover crop for managing SCN populations. When cereal rye is planted in rotation with soybean crops, it can help to reduce SCN populations in the soil. Cereal rye is a non-host crop for SCN, which means that it does not support the nematode’s reproduction.

In addition, cereal rye has allelopathic properties that can inhibit SCN reproduction and development. Cereal rye roots exude compounds such as benzoxazinones, which can suppress nematode egg hatching and inhibit nematode mobility.

Furthermore, cereal rye can improve soil health and fertility when used as a cover crop. Cereal rye has a deep root system that can help to break up soil compaction and improve soil structure, and it can add organic matter to the soil and improve nutrient availability.

Overall, cereal rye can be a useful component of an IPM strategy for managing SCN. Cereal rye can reduce the nematode population in the soil by acting as a non-host crop and producing allelopathic root exudates. It can also improve soil health and fertility, which can benefit subsequent soybean crops.

3. Clover

Clover is a non-host for SCN, and its root exudates can suppress SCN populations in the soil.

Clover, such as red clover (Trifolium pratense), can be an effective cover crop for managing SCN populations. When clover is grown in rotation with soybean crops, it can help to reduce SCN populations in the soil.

Clover is a non-host crop for SCN, which means that it does not support the nematode’s reproduction. Additionally, clover can add nitrogen to the soil through biological nitrogen fixation, which can improve soil fertility and benefit subsequent soybean crops.

Furthermore, clover can exude phytochemicals and other substances that can inhibit SCN reproduction and development. For example, clover root exudates can contain flavonoids and other compounds that can limit nematode mobility and reduce nematode feeding.

Overall, clover can be a useful component of an IPM strategy for managing SCN. Clover can reduce the nematode population in the soil by acting as a non-host crop and producing nematode-inhibiting root exudates. Additionally, clover can improve soil fertility and provide other benefits as a cover crop in a crop rotation system.

4. Mustard

Mustard (Brassica spp.) is a non-host for SCN and its allelochemicals can suppress SCN populations in the soil. Mustard can be an effective cover crop for managing soybean cyst nematode (SCN) populations. When mustard is grown in rotation with soybean crops, it can help to reduce SCN populations in the soil.

Mustard has several mechanisms by which it can suppress SCN reproduction and development. For example, mustard roots exude compounds such as glucosinolates that can suppress nematode activity and reduce nematode populations in the soil. Glucosinolates break down into compounds such as isothiocyanates and nitriles, which can have nematicidal properties. In addition, mustard can stimulate the growth of beneficial soil microbes that can suppress nematodes.

Furthermore, mustard can improve soil health and fertility. Mustard has a deep root system that can help to break up soil compaction and improve soil structure, and it can add organic matter to the soil and improve nutrient availability.

Overall, mustard can be a useful component of an IPM strategy for managing SCN. Mustard can reduce the nematode population in the soil by producing nematode-inhibiting root exudates and stimulating the growth of beneficial soil microbes. It can also improve soil health and fertility, which can benefit subsequent soybean crops.

5. Wheat

Wheat (Triticum aestivum) is a non-host for SCN and its deep root system can improve soil health and reduce soil compaction, making it less favorable for SCN growth.

Wheat can be an effective cover crop for managing SCN populations. Wheat is a non-host crop for SCN, which means that it does not support the nematode’s reproduction.

In addition, wheat can produce allelochemicals (such as benzoxazinoids, coumarins, and phenolic acids) which are chemicals that are toxic to nematodes. These allelochemicals can help to suppress SCN populations in the soil.

Furthermore, wheat can add organic matter to the soil and improve nutrient availability. Wheat has a fibrous root system that can help to break up soil compaction and improve soil structure. This can create an environment that is less favorable for SCN development and reproduction.

Overall, wheat can be a useful component of an IPM strategy for managing SCN. Wheat can reduce the nematode population in the soil by acting as a non-host crop and producing allelochemicals that are toxic to nematodes. It can also improve soil structure and fertility, which can benefit subsequent soybean crops.

Conclusion

Overall these cover crops can engage various modes of action to control the SCN population in the soil. The most common mode of action involved the production of toxic or suppressive root exudates or allelochemicals against SCN. But, also many cover crops exhibiting fibrous or well-developed root systems can improve soil structure by increasing soil organic matter, reducing soil compaction, and acting as a physical barrier to SCN movement in the soil. Also, some cover crops increase soil fertility through biological nitrogen fixation to support soybean health and immunity to nematodes. These cover crops exhibit a unique potential to control SCN in fields and can be incorporated into an IPM program for nematode control.

Sources for additional information

• Chen, S., Wyse, D. L., Johnson, G. A., Porter, P. M., Stetina, S. R., Miller, D. R., … & Haar, M. J. (2006). Effect of cover crops alfalfa, red clover, and perennial ryegrass on soybean cyst nematode population and soybean and corn yields in Minnesota. Crop science, 46(5), 1890-1897.
• Miller, D. R., Chen, S. Y., Porter, P. M., Johnson, G. A., Wyse, D. L., Stetina, S. R., … & Nelson, G. A. (2006). Rotation crop evaluation for management of the soybean cyst nematode in Minnesota. Agronomy Journal, 98(3), 569-578.
• Neupane, K., Yan, G., & Plaisance, A. (2022). Evaluation of cover crops for reducing Heterodera glycines populations in microplot experiments. Nematology, 1(aop), 1-13.
• Rocha, L. F., Pimentel, M. F., Bailey, J., Wyciskalla, T., Davidson, D., Fakhoury, A. M., & Bond, J. P. (2021). Impact of wheat on soybean cyst nematode population density in double-cropping soybean production. Frontiers in Plant Science, 12, 640714.
• Wen, L., Lee-Marzano, S., Ortiz-Ribbing, L. M., Gruver, J., Hartman, G. L., & Eastburn, D. M. (2017). Suppression of soilborne diseases of soybean with cover crops. Plant disease, 101(11), 1918-1928.