Early season considerations for managing SDS
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
The heavy rains we have had created favorable conditions for the fungus that causes SDS, Fusarium virguliforme. With the clock ticking and unfavorable conditions for planting in many fields, it’s unlikely that any plantings you’re doing now would be considered early, but there are still some important considerations.
Choose resistant varieties to limit yield loss. Research shows that there is a definite relationship between SDS and the soybean cyst nematode. Although soybean cyst nematodes are not required for the development of SDS, it increases its severity. It’s important to look at both soybean cyst nematode-resistance and SDS-resistance levels when deciding which varieties to plant in a field with a history of SDS. Even when soybean cyst nematode-resistant soybeans are used, SDS may be more severe in fields with a history of high levels of soybean cyst nematodes. Because soybean cyst nematodes are usually present in fields with SDS, it’s advisable to choose and soybean cyst nematode-resistant soybean that has at least moderate resistance to SDS. Growers requiring group II and shorter maturity soybeans have fewer choices for SDS resistant varieties than longer maturity groups, but there are some varieties available.
Avoid early planting, especially if fields have a history of SDS. Yield reductions due to SDS are dependent on when infections begin. Early infections result in pod abortion, reduced seed number and size. Avoid early planting, especially in soils that are cold and wet. SDS is often less severe in delayed plantings and in early maturing cultivars, as the onset of the disease doesn’t occur until later reproductive stages.
Evaluate your tillage practices. Severity of SDS tends to be greater under no-till or reduced tillage systems than conventional tillage. Reasons for this may include higher soil moisture, cooler soil temperatures and higher loads of the pathogen remaining as inoculum for subsequent soybean crops.
Improve drainage. SDS is often found in wet areas or poorly drained soils.
Minimize soil compaction. Wetter, less porous soils resulting from compaction favor the development of SDS. The excess amounts of rain we have had put growers behind on planting schedules and make it more tempting to go out and work in fields that are still too wet. Don’t be tempted; the drawbacks will far outweigh the benefits.
Avoid moving infested soil from field to field on equipment or vehicles. Work clean fields before working fields that have a known history of soybean cyst nematodes or SDS. Wash off soil from equipment after working in a field with soybean cyst nematode or SDS. The fungus responsible for SDS can survive for extended periods in soil, and has been found in soybean cyst nematode cysts.
Crop rotation is not a primary management tool for SDS, because the fungus produces resting spores in the soil, and can survive for extended periods in the soil, but rotating out of soybeans for at least two years does help to reduce soybean cyst populations and may indirectly help reduce SDS.