SDS in soybeans

Assessing SDS and SCN

By Grant Collier, MS, Regional Sales Agronomist, Ohio, Stine Seed Company

It’s another growing season in the great state of Ohio, and with that came another exceptionally wet spring. Among the many pathogens present, sudden death syndrome (SDS), is once again reminding us why it is in the top two most destructive soybean diseases in the U.S. The moisture, in combination with the cooler periods of weather, created prime periods for fungal infection. When environmental conditions are favorable, infection can occur early in the growing season. When exposed to these conditions, early planted soybeans are most susceptible to infection due to an extended infection period. Unfortunately, soybean cyst nematode (SCN) is the most destructive soybean disease and is often found in conjunction with SDS. Though a quick cure does not currently exist, growers do not need to hit the panic button. Here are a few tips to help control SDS. 

Grant Collier, MS, Regional Sales Agronomist, Ohio, Stine Seed Company

Growers will want to target soybean varieties with some partial resistance to SDS. Pay attention to the varieties you are planting to ensure that you are choosing soybean lines that have — at minimum — partial resistance to SDS. Be sure to place these varieties on the infected fields in the coming season. 

Resistance to SCN can also be an effective form of control to help slow the progression and severity of SDS. Companies, such as Stine Seed Company, are offering more soybean varieties with the Peking gene for SCN resistance to be packaged along with the more commonly known PI88788 trait. Peking is an older trait that many companies maneuvered away from, when the PI88788 resistance trait was discovered. However, despite being an older trait when rotated into your lineup, these varieties are proving to provide an effective alternative control against SCN. 

In addition, minimizing tillage is essential to limiting the spread of SDS throughout your field, as well as SCN. Tillage equipment will drag the fungi spores from problem areas in the field to areas that were otherwise unaffected. Cyst eggs often occur in pockets throughout an infected field. Tillage equipment will also drag SCN eggs through the field, causing cyst symptoms to generally occur in circular or ovular patterns. You can visualize where the cysts pockets are located, and dragged through the soil by equipment. 

Another cultural method of control, albeit one of the most important methods, is crop rotation. Diversify away from soybeans and corn in your problem fields as much as possible. The more crops in the rotation, the better. Many believe that rotating to corn for a year is an effective method against SDS; however, studies have shown that both corn and soybeans can provide a safe haven for the disease to persist in the soil. 

Plant your infected fields last, when the soil conditions are warmer and drier. Also, be sure to identify your problem areas to see if there is SCN present. 

Growers will want to collect soil samples from the problem areas throughout the field. Sample the top 8 inches to 10 inches of the soil using a soil probe. Cysts are most likely to be found in the lighter, sandier soils such as sand knobs or lake beds. I recommend taking multiple samples from an infected field, and mixing them together in order to collect a composite sample for testing. Send the samples in to a soil testing lab and have them check for cyst egg count. 

Lastly, there are several seed treatments available for SDS and SCN on the market today. These treatments can be costly and irrelevant if the field does not have SCN/SDS. It is also important that these treatments, if applied, be used in conjunction with all of the other control methods available. After samples are analyzed, and eggs are counted per cc of soil, it can be determined if SDS/SCN seed treatments may be worth trying in 2022.

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