SCN Egg Counts Surpisingly High

Published on 31 Oct 2017, 08:00 AM • by: Dan Davidson, Illinois Soybean Association • 270 Views

SCN egg counts were surprisingly high in a Southern Illinois survey.

The Illinois Soybean checkoff is funding an SCN (Soybean Cyst Nematode) study to look at the impact of wheat straw on SCN populations and an initial screening survey reported higher than anticipated eggs counts. Data from a University of Kentucky study in the early 1990s indicated that no-tilling soybeans into wheat stubble where straw remained intact on the surface reduced egg count and suppressed egg production in the next double cropped soybean crop. If these findings are true and repeatable adding wheat to the rotation before planting soybeans can provide another tool for controlling SCN.

In this study, the research team screened 22 potential fields in Southern Illinois. The goal was to identify ten fields that fell into one of three categories of low, moderate and high egg counts for the study. We reached out to farmers who volunteered to collaborate; pulled composite soil samples from fields going into the winter wheat double crop soybean rotation; and Jason Bond, pathologist at Southern Illinois University ran egg counts on the soil samples. Dr. Bond developed criteria for selecting fields for inclusion in the study (below).

The results, shown on the left below, had egg counts ranging from a low of 0 to a high of 37,600. And in most cases, counts higher than 2,000 are a concern and show that are management practices don’t seem to be working as anticipated. Fourteen of 22 samples had eggs counts greater than 2,000.

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Controlling SCN is challenging today. Rotations with corn and planting resistant varieties aren’t a total cure-all so today seed treatments can be added to the list of control methods and perhaps adding wheat into the rotation will be an additional control tool.

SCN pest levels may be higher than you think and particularly if you aren’t monitoring populations in the soil. Don’t be caught with higher than expected egg counts or your yield expectations won’t be realized. In fields going to soybeans in 2018, pull soil samples and check egg counts to see if you are controlling populations and your management strategies are working.

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

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