With the prevalence of Soybean Sudden Death (SDS) in the Kansas River Valley, multiple studies involving SDS have been conducted at Kansas River Valley Experiment Field the past several years. The following is a summary of several of the studies that provide some clues on how to reduce the severity of SDS and improve the profitability of soybeans.
Soil fertility
The first step to help reduce the severity of SDS is proper fertility. Results from a long-term macronutrient fertility study at the Kansas River Valley Experiment Field with a corn/soybean rotation have shown that soil phosphorus (P) levels can have a significant influence on the severity of SDS (Table 1). During the soybean rotation phase of the study in 2014 and 2016, SDS symptoms increased significantly as P fertility decreased.
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Table 1. Effects of P applied to corn on sudden death syndrome (SDS) and yield of soybean, Kansas River Valley Experiment Field, average of 2014 and 2016. |
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P rate on corn |
Soil Test P |
2014 Leaf phosphorus |
SDS severity |
NDVI1 |
Height |
Yield |
|
(lb/acre) |
lb/acre |
(ppm) |
(% foliage affected) |
|
(in.) |
(bu/a) |
|
0 |
13 |
0.15 |
40.3 |
0.768 |
32.2 |
40.3 |
|
30 |
30 |
0.18 |
27.7 |
0.795 |
37.8 |
52.5 |
|
60 |
92 |
0.26 |
16.2 |
0.809 |
39.3 |
61.2 |
|
LSD (0.05) |
8.8 |
0.01 |
10 |
0.013 |
1.5 |
4.3 |
1 Normalized difference vegetation index.
After more than 30 years with no P added prior to the corn crop, the P level in the top foot of soil was 13 lbs per acre, compared to 92 lbs per acre where 60 lb of P2O5 had been added every other year. Where no P had been applied, the percent defoliation by SDS at R6 averaged 39% in 2014 and 2016 compared to 16% with the 60-lb rate, resulting in a yield increase of 21 bu/acre or more than 50%.Nitrogen and potassium rates applied to the corn had little or no effect on SDS symptoms in soybeans. Paying attention to P levels in the soil is an important step to reduce the severity and yield loss to SDS.
Variety selection
The next step in management of SDS is the selection of soybean varieties that have tolerance or resistance to SDS, with good yield potential. Yields of soybean varieties can differ greatly when SDS is present. Entries in the Kansas Soybean Performance Variety Trials have been rated for severity of SDS at the Kansas River Valley Experiment Field over the last several years (Figure 1). Significant differences in the severity of SDS and seed yield have been observed between varieties (Figures 2 and 3). Each year over the past 3 years SDS severity and seed yield have been negatively correlated, with a yield range of more than 20 bu/acre. Proper variety selection can result in significant yield increases in the presence of SDS.
Figure 1. Sudden Death Syndrome: tolerant vs. susceptible soybean varieties at the Kansas River Valley Experiment Field, Rossville. Photo by Eric Adee, K-State Research and Extension.
Figure 2. Average area under disease progress curve (AUDPC) for SDS for top 5 most resistant and bottom 5 most susceptible (to SDS) varieties in the irrigated soybean performance trial at the Kansas River Valley Experiment Field.
Figure 3. Average yield of top 5 most resistant and bottom 5 most susceptible (to SDS) varieties in irrigated soybean performance trial at the Kansas River Valley Experiment Field.
Seed treatment
A number of compounds have been tested at the Kansas River Valley Experiment Field for their effectiveness in reducing the severity and yield loss to SDS, including seed treatments, and in-furrow and foliar-applied products. Some of the more promising products have been seed treatment and in-furrow products. However, currently only one product, ILeVO (Bayer), has successfully made it to market. Over several years of data at the Kansas River Valley Experiment Field, the seed treatment, ILeVO (fluopyram), has increased soybean yields by more than 30%, or 12 bu/acre, in soybeans with high levels of SDS (Tables 2 and 3), and more than 2.6%, or 2 bu/acre, when the severity of SDS was low (Table 4).
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Table 2. Influence of variety and seed treatment for Sudden Death Syndrome on yield of soybean, Kansas River Valley Experiment Field-Rossville, 2013 |
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Soybean varieties |
Most resistant |
Moderately resistant |
Susceptible |
Most resistant |
Moderately resistant |
Susceptible |
|
Seed treatments |
Yield (bu/acre) |
% leaf area with SDS at R6 |
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|
Check |
28.6 |
29.2 |
21.3 |
18 |
44 |
63 |
|
ILeVO1 at higher rate |
41.6 |
39.7 |
37.4 |
4 |
28 |
45 |
|
ILeVO at lower rate |
42.9 |
41.0 |
26.2 |
5 |
28 |
72 |
|
LSD 0.05 |
8.3 bu/A |
17.4% |
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1 Bayer CropScience (Research Triangle Park, NC).
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Table 3. Influence of seed treatment for Sudden Death Syndrome on yield of soybean (Stine 43RE02), Kansas River Valley Experiment Field-Rossville, 2014 |
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Seed treatments |
Yield (bu/acre) |
SDS Severity (% leaf area at R6) |
SDS Severity (AUDPC) |
NDVI |
|
Check |
47.4 g |
52 a |
696 ab |
0.834 bc |
|
ILeVO1 (0.15 mg) |
59.6 a |
16 bc |
146 c |
0.846 ab |
|
ILeVO (0.075 mg) |
57.0 d |
31 ab |
443 bc |
0.835 bc |
|
LSD 0.05 |
0.06 |
22.9 |
354 |
0.021 |
1 Bayer CropScience (Research Triangle Park, NC).
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Table 4. Influence of seed treatment for Sudden Death Syndrome on yield of 5 soybean varieties with ranges of tolerance to SDS, Kansas River Valley Exp. Field, 2015 |
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Variety (in order of resistance) |
Yield (bu/acre) |
SDS Severity (% leaf area @R6) |
SDS Severity (AUDPC) |
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|
|
Without ILeVO1 |
With ILeVO |
Without ILeVO |
With ILeVO |
Without ILeVO |
With ILeVO |
|
A (most resistant) |
67.7 |
69.5 |
1.2 |
1.2 |
17 |
13 |
|
B |
58.0 |
58.6 |
2.3 |
2.3 |
56 |
34 |
|
C |
57.1 |
59.2 |
4.7 |
1.2 |
45 |
16 |
|
D |
60.7 |
64.5 |
20.0 |
11.2 |
518 |
102 |
|
E (least resistant) |
55.4 |
61.1 |
21.1 |
4.7 |
345 |
94 |
|
LSD 0.10 |
4.2 |
8.1 |
94 |
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1 Bayer CropScience (Research Triangle Park, NC).
Planting date
Traditionally, soybean planting dates in the Kansas River Valley have been delayed until after mid-May to help avoid the development of SDS. For the last two years in planting date studies at the Kansas River Valley Experiment Field, SDS symptoms have been more severe in earlier plantings (first of May). As the planting dates progressed later the severity of SDS decreased. However, the highest yields in these studies occurred with the earlier planting dates, in spite of the increase in SDS. Yields decreased by an average of almost 0.5 bu per day for more tolerant varieties when planting was delayed after the end of April/first of May, and 0.3 bu per day for the more susceptible varieties. In both years of these studies, the severity of SDS was not as high as previously observed at the Kansas River Valley Experiment Field.
Summary
Based on research over several years at the Kansas River Valley Experiment Field there are several management practices that can help reduce the yield loss to SDS. Those measures include proper soil P levels and planting the best variety with fluopyram seed treatment applied as early as agronomically practical.
These practices have significantly increased soybean yields in fields in the Kansas River Valley that regularly have SDS. Research continues to help fine-tune and improve the management of growing soybeans with the risk of SDS.
Eric Adee, Agronomist-in-Charge, Kansas River Valley and East Central Kansas Experiment Fields
eadee@ksu.edu
Bill Schapaugh, Soybean Breeder
wts@ksu.edu
Dorivar Ruiz-Diaz, Nutrient Management Specialist
ruizdiaz@ksu.edu
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
ciampitti@ksu.edu
Chris Little, Plant Pathologist
crlittle@ksu.edu
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