Soybean cyst nematode (SCN) is one of the most destructive pathogens. Research has shown the presence of SCN increases the risk of sudden death syndrome (SDS), which continues to spread across the Midwest. For three years, the Farm Journal Test Plots team has been studying new genetics and seed treatments to manage SCN and SDS on the front end since there are no in-season treatment options.
Can yield & economics improve with SCN-resistant varieties & seed treatments?
In southern Michigan, two varieties were planted in sandy loam soils in three locations in 2017 and 2018, and two in 2019. One variety contained PI88788 genetics with resistance to SCN races 14 and 3, and the second featured Peking genetics with resistance to races 14, 5, 3 and 1. Each variety was evaluated three ways: Ilevo (1.18 fl. oz. per 140,000 seeds) with a fungicide/insecticide (F/I); F/I only; and no seed treatment.
Using seed treatments improved yields across all plot locations each year. The PI88788 with Ilevo and F/I combo resulted in the biggest yield benefit at 4.99 bu. and net gain at $25.63 per acre versus the check.
The PI88788 genetics and F/I only treatment increased yield 2.30 bu. and ROI $10.33 per acre compared with the check. Therefore the Ilevo portion yielded 2.7 bu. and $15.30 more per acre.
In the Peking genetics, the response to the F/I only treatment was similar to PI88788, also increasing yields 2.30 bu. per acre versus the check. However, the Ilevo portion only increased yields 1.70 bu. with a net gain of $5.73 per acre compared with the F/I only treatment.
In comparing genetics only, across all locations and years, the Peking and PI88788 genetics yielded similar.
”Since SCN pressure was low, the added race resistance in the Peking genetics might not have had an advantage,” says Farm Journal Field Agronomist Missy Bauer.
The yield increase from the Ilevo seed treatment was likely due to the stay-green effect later in the season. The strips with the Ilevo stayed greener later versus the F/I only and non-treated check.
”This late-season stay-green effect can extend the grain fill period,” Bauer says. ”Keeping plants greener longer can help improve seed size and increase yields.”
In 2018, the highest response year, seed size in one location differed 188 seeds per pound, which is equivalent to 4 bu. per acre. The conditions in August and September 2018 provided adequate moisture to take advantage of plant greenness by improving seed size, Bauer explains. In 2019, the seed size improvement with Ilevo was equivalent to 1.3 bu per acre.
”The yield increase from the F/I seed treatment could have been due to an overall healthier plant and a slight difference in population,” she adds. ”Population stand counts did improve with the F/I seed treatment compared with no treatment.”
Is it possible to reduce SCN in-season with genetics & seed treatments?
Because SCN pressure was low, it was difficult to determine if the Ilevo seed treatment or the Peking genetics reduced pressure. However, in locations that had more SCN pressure, the Peking variety had lower SCN levels at harvest all three years, Bauer says.
In 2017, the locations with more pressure did have fewer SCN later in the season with the Ilevo. However, in 2019, the Ilevo seed treatment didn’t seem to change the SCN count, but there was a lot of variability in pressure.
Bauer recommends sampling soil for SCN to determine the extent of the pressure.
Is there visually fewer SDS symptoms when using Ilevo seed treatment?
In the three years and eight test plots, only one location had visual SDS pressure, which occurred in 2018. The SDS incidence counts (the percent of plants with visual symptoms late in the season) were the highest in the non-treated seed at 29%. The F/I treatments averaged 12.5% SDS, and the Ilevo seed treatments averaged 3%.
”Based on test plot data, the Ilevo seed treatment was able to reduce SDS incidence counts,” Bauer says.
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Thank You to Our Test Plot Partners
BASF, Bayer Crop Science, Pioneer, Can-Am, Case IH, Clarks Ag Supply, Great Plains, Kinze, New Holland, Unverferth, AeroVironment, AirScout, Trimble, Bob and Mary Kochendorfer, Finegan Farms, North Concord Farms, Bracy Ag Services and Michigan Soybean Promotion Committee