Spread of soybean sudden death syndrome evident across southwest Michigan fall 2014
Soybean sudden death syndrome can be found at low levels in many southwest Michigan fields this fall. Growers should evaluate fields and think about selecting partially resistant varieties where SDS has been on the rise.
Farming is risky business these days. Prices are falling as world grain stocks are recovering to near normal levels after several years of production challenges from poor weather conditions. As prices fall, managing crops to protect profitability is more important than ever. Soybean producers in southwest Michigan are facing a growing threat to soybean profitability. That threat is being caused by the spread of soybean sudden death syndrome (SDS).
Soybean sudden death syndrome is caused by a root infection of the fungal pathogen Fusarium virguliforme. Cool and wet conditions this spring and late summer rainfall helped to spur on symptoms of the disease this year, especially in portions of the fields that had compaction issues. The disease is often, but not always, associated with high levels of soybean cyst nematode infestation. While the infection takes place in the roots, foliar leaf symptoms occur when toxins from the root infection impact leaf growth in the plant canopy. Premature defoliation causes the most significant yield losses.
Don’t think you have SDS in your fields yet? We think that you might want to take a little closer look at your fields. The disease can be very subtle in appearance, escaping detection without a close inspection. Some late SDS symptom development may not significantly impact soybean yields, but the challenge with this disease is that it tends to slowly and subtly accumulate in the soil. Under the right conditions, SDS can cause significant yield losses.
The disease is spreading across the region. Field observation transects conducted in western Van Buren and northern Berrien counties in late August revealed that 32 out of 47 fields walked, or 68 percent, had at least some levels of SDS that could be seen in the leaf canopy. We didn’t have to walk too far in each field to find evidence of the disease. Field transects in previous years showed infection rates of around 20-25 percent incidence of SDS in other areas of southwest Michigan in 2013, up from around 10-15 percent in previous samplings conducted in 2011.
We are not suggesting that all of the fields that have minor leaf symptoms are likely to have significant yield losses from SDS this season. A few of the more infected fields will have low to moderate yield losses in 2014. However, it is important for growers to recognize that the disease, once identified in the field, is likely to continue to accumulate. SDS is somewhat unique in that it can survive on corn residues and be ready to infect soybean plants when the rotation returns to beans. If you happen to plant a highly susceptible SDS variety into a field that has significant SDS pressure, you might be in for an expensive surprise.
SDS resistance screening conducted at Michigan State University’s soybean disease research site, located near Decatur, Michigan has shown the value of planting varieties that have partial resistance or tolerance to SDS. There can be differences in yield potential of 30 bushels per acre or more between soybean varieties in highly infected fields. Michigan State University Extension encourages growers that have SDS in fields to consider planting varieties that the companies have rated as their most resistant in fields that show significant SDS pressure. However, the most important step in that process is identifying the disease and knowing if it is present in the field. The best time to evaluate the incidence of SDS is by looking at the fields one to two weeks prior to senescence (leaf drop). Then, growers should concentrate on minimizing soil movement out of these infected fields and selecting the right varieties.
Research being conducted in Decatur, Michigan by MSU field crop pathologist Martin Chilvers is evaluating the effectiveness of incorporating various seed treatments in combination with partially resistant varieties in reducing the yield reduction of SDS. Results of this work are anticipated being presented at MSU Extension winter crop management programs.
SDS is becoming more prevalent in southwest Michigan soybean fields. Early identification of the disease, selecting partially resistant varieties and minimizing soil movement out of these fields can help growers to manage risk of yield losses from this growing threat to profitability.
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