With the 2022 planting season just around the corner, now is a great time to fine-tune plans for your upcoming crops. Farmers in corn-soybean rotations or rotating from continuous corn to soybean, because of high input costs or heavy corn rootworm pressure, should take time to consider the various factors that may negatively impact soybean yield potential.
Planning ahead to determine if and how to manage the factors you have some control over, may contribute to the difference between a good or a poor performance year. Sudden death syndrome (SDS) is an example of a disease where developing a management game plan well in advance of planting may help to increase dividends.
SDS is caused by the fungus Fusarium virguliforme, and it is one of the leading yield robbing diseases of soybean in the United States annually. The SDS pathogen causes root rot, which often does not have any obvious above ground symptoms. It also produces a toxin that is responsible for causing the foliar symptoms associated with this disease, which include interveinal chlorosis and necrosis (Figure 1), leaf loss where the petioles remain attached to the stems (Figure 2), pod and seed abortion, reduced seed size, and premature death of the soybean plant. Heavy rainfall, moist conditions, or excessive irrigation during the mid- to late soybean reproductive stages help the toxin move up the stem to the leaves. Foliar symptoms of SDS may be easily confused with other common soybean diseases such as brown stem rot and stem canker.
Crop rotation fails to reduce the levels of SDS inoculum in fields. Corn serves as an asymptomatic host for SDS during the growing season, and the fungus can overwinter in the soil, on corn residue, dropped ears, and dropped kernels.1,2 The SDS pathogen can also infect several other legume crops, including alfalfa and red clover, and weeds such as pigweed and lambsquarter may serve as asymptomatic hosts.2
Management tactics to help reduce the negative impact of SDS include product selection and soybean seed treatments. SDS severity may be greater in fields infested with Soybean Cyst Nematode (SCN). Fields should be monitored for SCN pressure and soybean products selected that possess resistance to SCN such as the PI88788 source of resistance. PI88788 is the most common source of SCN resistance used in soybean seed production today. The Peking source of SCN resistance is also available in a few soybean products.
Additionally, select soybean products with good genetic tolerance to SDS; however, keep genetic yield potential in mind because some products with good genetic tolerance to SDS may have reduced yield potential. Currently, there are no soybean products on the market that are completely resistant to SDS. However, there are soybean seed treatments, such as ILeVO® seed treatment and Saltro® fungicide seed treatment that may help protect soybean plants from SDS. These products are also labeled to help manage SCN, based on the application rate. It is important to note that these seed treatments are labeled to help protect soybean plants from SDS and SCN but not to eliminate infections from occurring. The portfolio of soybean products to choose from may be increased when deciding to use seed treatments because of the protection they offer to soybean products that have less SDS tolerance but have other desired characteristics, such as increased yield potential. That decision depends on the amount and type of risk each individual farmer is willing to assume.
SDS infections usually occur early in the spring when soils are cool and wet. Therefore, ensuring fields have adequate drainage is important. Experience has shown SDS infections commonly occur in areas of soil compaction because water is prevented from percolating through the soil profile. This causes compacted areas to stay wetter longer and exposes soybean plants in those areas to greater risk for infection if the Fusarium virguliforme pathogen is present. It is also recommended to consider planting fields with a history of SDS a little later when soils are potentially drier and warmer; however, do not plant so late that yield potential is negatively impacted.
For more information about SDS, please contact your local Channel Seedsman and read “Soybean Sudden Death Syndrome”.
1Mueller, D., Leandro, L., and Robertson, A. 2020. Soybean sudden death syndrome and the 2020 derecho. Integrated Crop Management. Iowa State University, Ames. https://crops.extension.iastate.edu/.
2Kolander, T.M., Bienapfl, J.C., Kurle, J.E., and Malvick, D. K. 2012. Symptomatic and asymptomatic host range of Fusarium virguliforme, the causal agent of soybean sudden death syndrome. Plant Disease 96:1148-1153. https://doi.org/10.1094/PDIS-08-11-0685-RE
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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