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Agronomy Day 2007

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Investing In The Future: SCN Management Today

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Eric Adee Eric Adee, Principle Research Specialist,
Department of Crop Sciences
Northwestern Illinois Agricultural Research
and Demonstration Center, Monmouth,

Spread of soybean cyst nematode Heterodera glycines (SCN) to much of the soybean (Glycine max) growing region in the Midwest has created a persistent and significant annual yield loss for soybean. Variety selection has been the primary tool to reduce yield loss to SCN. It is not known how moderately resistant varieties fit into the management of SCN. Moderately resistant varieties can have high yield potential, but nematode reproduction is greater than on resistant varieties. Additionally, it is not known how soybean varieties with some form of SCN resistance can affect the SCN population and future soybean crops. Two varieties each of resistant, moderately resistant and susceptible to SCN were planted in the same plots for two soybean crops in annual rotation with corn. SCN populations and yields were quantified. The SCN population was reduced 80 and 54%, respectively, by resistant and moderately resistant, and increased 189% by the susceptible. Yields of the resistant and moderately resistant were 8.2 and ll.8 bu/ac better, respectively, than with the susceptible. A bioassay of the plots with a susceptible variety showed there was a carry-over effect from the variety selection for the previous two soybean crops. The bioassay yields following resistant and moderately resistant were 6.6 and 4.3 bu/ac better than following susceptible varieties.

This study shows the benefit of incorporating varieties with some degree of resistance to SCN for SCN management, which includes those classified as moderately resistant. Utilizing results from university variety trials in combination with information on the SCN resistance of a variety will not only improve the profitability of the current soybean crop, but the carry over benefit to subsequent soybean crops will be the reduction of SCN population. The improvements in genetics and information sources have given growers the tools necessary to make good decisions to limit yield losses to SCN.

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Effect of level of SCN resistance on SCN population in a corn/soybean rotation. Data points are averages of 2 varieties, 4 replications and two fields. Corn was planted between the first fall and the second spring, and the second fall and the third spring.

Effect of prior planting of SCN resistant varieties for two crops on yield and height of a susceptible soybean in corn/soybean rotation.
Level of SCN Resistance in 2 Varieties SCN Population at Planting (eggs/100cc) Soybean Bioassay Averages
of 2005 and 2006
Height (in.) Yield (bu.)
Resistant 625 33.6 44.3
Moderately Res. 1598 32.0 42.0
Susceptible 6093 29.4 37.7
LSD 0.05 2060 1.4 4.1