SDS and brown stem rot in soybean
Sudden death syndrome, or SDS, has been observed in soybean fields in Indiana over the last week. The fungus that causes SDS, Fusarium virguliforme, infects soybean early, and symptoms are typically expressed later in the growing season. Many soybeans throughout Indiana emerged from wet soils this spring, and growers should be watching for symptoms of SDS in fields over the next few weeks.
Symptoms of SDS are expressed as interveinal yellowing and necrosis. Veins of symptomatic leaves will remain green. Leaflets will curl or shrivel and drop off with only the petiole remaining. The disease brown stem rot (BSR) has also been identified in a few fields in Indiana. Foliar symptoms of this disease can resemble foliar symptoms of SDS and it is important to split the lower stem of symptomatic plants to determine which fungal disease is present. BSR can cause internal stem browning, resulting in a dark brown discoloration of the pith at the lower nodes of the plant. The pith of plants affected by SDS will remain white, while the tissue below the epidermis will have brown to gray discoloration present.
SDS and BSR are diseases best managed through preventative methods. Producers are encouraged to plant varieties that are less susceptible to SDS and BSR in fields with a history of the disease. However, varieties that are resistant to SDS may not be resistant to BSR, so it is important to properly diagnose plants in each field. SDS is typically more problematic in early-planted soybeans, although if soil and weather conditions are favorable for infection, later planted soybeans are also at risk for disease development. Other factors such as soil compaction and high soybean cyst nematode populations may increase severity and impact of these diseases. Foliar fungicide applications are not recommended for management of SDS or BSR.
Purdue is involved in a multi-state project funded by USDA-NIFA to improve our understanding of the fungus that causes SDS and develop new management practices for the disease. This year, we are looking to sample SDS from soybean fields across Indiana. If you know of a field that has SDS, please contact Kiersten Wise at firstname.lastname@example.org, or 765-496-2170.