Warm Temperatures Roll Out Welcome Mat for SCN

Soybean cyst nematode (SCN), the No. 1 yield-robbing pest in soybeans, made an early appearance this summer. As a result, the pest has the potential to show up in full force and cause greater crop damage.

“It typically takes five to six weeks or more after planting for the first SCN females of the growing season to develop and appear on roots,” said Greg Tylka, Iowa State University professor in the Department of Plant Pathology and Microbiology and a leader of the SCN Coalition, in a recent report. “The appearance of SCN females on soybean roots just 26 days after planting is as early as I have seen.”

SCN females most likely developed this early due to the warm temperatures across Iowa in May, he noted. The soybean plants he observed were planted May 10.

Finding the pest this early could mean trouble for the rest of the season.

“The appearance of the white adult SCN females on the roots indicates the first generation of the nematode is being completed,” Tylka said. “The nematode will continue to reproduce in successive generations though the season and into the fall. If above-average temperatures persist, there may be more generations of SCN produced in the 2018 growing season than in a season with cooler temperatures.”

Each female produces 250 or more eggs each generation, and new generations can spawn as quickly as every 24 days. With resistance to the most common soybean genetics, PI 88788, on the rise, higher populations could be troubling for farmers.

Fields with PI 88788 are yielding about 14 bu. per acre less than when SCN was controlled. According to the SCN Coalition, less than one in 10 SCNs should be able to reproduce to warrant adequate control. Today, more than 50% of the SCN population is successfully reproducing in fields with PI 88788 genetic resistance—which represents approximately 95% of all resistance.

Take note of where you’re seeing nematodes this year and keep that in mind when buying inputs for next season. It might be valuable to use a SCN-resistant variety as well as a seed treatment.

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