Soybean cyst nematodes (SCN) and root knot nematodes are both major pests in soybeans and reduce field yield potential. Genetic resistance is imperfect and the best solution is to rotate away from soybeans for at least a year or maybe longer if egg counts are in the thousands. Fortunately, a couple of seed treatments have come along that provide some additional control as part of a set of best management practices that includes crop rotation and genetic resistance. Those two products, VOTiVO® from Bayer and Clariva® from Syngenta, are applied to seed in combination with fungicides and insecticides.

There is an additional commercial seed treatment product available that has some efficacy against these roundworms. Plant Health Care’s N-Hibit®, a commercial seed treatment product that contains the harpin protein, shows some efficacy for control of SCN in soybeans, but results are inconsistent.

The harpin protein stimulates the plant’s internal self-defense mechanisms and helps the roots resist roundworms.

Harpin proteins, isolated from the bacterium Erwinia amylovora, were discovered in 1992 at Cornell University. The discovery was reported in the journal Science in 1992 (Vol 257, Issue 5066, p. 85-88). Use of the harpin protein in this regard was patented by the Cornell University scientists in 1998. Harpin proteins activate a naturally occurring process in the plant, boosting the plant’s immune systems in order to fight off diseases. They do this by tricking the plant into thinking it is under attack by plant pathogens—except there are no harmful pathogens present.

Plant Health Care markets N-Hibit seed treatment containing the harpin protein. Iowa State University conducted nine experiments in 2007 to determine the effects of N-Hibit on SCN reproduction and soybean yield. A total of six of the nine experiments had greater yields than the untreated plots. In two of the nine, SCN-susceptible soybeans treated with N-Hibit had significantly greater yields than untreated SCN-susceptible soybeans. In 2008 N-Hibit did not significantly impact yield at any of the nine locations. And in both years N-Hibit did not reduce SCN population densities at the end of the season. You can read the results by clicking here and here.

While applications of the harpin protein may elicit a plant response and prevent infection and infestation, it may not be as reliable as the other commercial seed treatments on the market when it comes to getting additional control of SCN.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at

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About the Author: Dan Davidson

Soybean agronomist Daniel Davidson, Ph.D., posts blogs on topics related to soybean agronomy. Feel free to contact him at or ring him at 402-649-5919.