Soybean sudden death syndrome increasing in southwest Michigan fields
Recent MSU pest management meeting survey shows soybean sudden death syndrome is on the rise in southwestern Michigan fields.
Soybean sudden death syndrome (SDS) has quietly, but steadily, been on the increase in southern Michigan soybean fields over the past few years. Its progression may be going somewhat unnoticed due to a lack of significant yield decreases because the disease symptoms have occurred later in the season. The usual impact of “late season onset SDS” is somewhat smaller soybean size rather than a reduction in pod count or beans per pod. However, SDS is a fungal pathogen that is somewhat of an accumulator disease, and the fact that it continues to be found in more areas warrants watching. Forty-three percent of the participants in a Michigan State University Extension southwest regional meeting indicated that they had seen an increase of SDS in their own or neighboring fields in 2013. This compares to 21 percent of participants reporting an increase in SDS in southeast Michigan and 20 percent in mid-Michigan (Alma, Mich.), which is still significant.
This increase in grower-reported SDS in southwest Michigan coincides with an SDS incidence transect we conducted in late August 2013 in St. Joseph and southern Kalamazoo counties. Fields were observed during a two-day survey for any visible evidence of SDS in both 2011 and 2013. In 2011, roughly 5 percent of the fields that were walked showed at least some incidence of late onset SDS. In 2013, that number increased to over 9 percent of the fields observed. Yield losses were probably low on almost all of the fields that were observed, but there were a few instances of lower pod counts and bean size due to earlier than normal leaf loss in heavier pockets of SDS in a few fields.
In addition to St. JosephCounty, there was also a visible increase in the incidence of SDS in northern Berrien and western Van Buren counties last fall.
What does this mean for soybean production on your operation if you find increasing incidence of SDS? It most likely means that it would be prudent to step up observation of when and where SDS is occurring on your farm. If you have fields that seem to be accumulating the disease, ask your seed dealers about sourcing varieties that have shown the most resistance to SDS. Also, check the fields for soybean cyst nematodes (SCN). SDS can occur without SCN infestations, but we have often seen the worst incidence of SDS where SCN numbers are high. Extended rotation to a crop other than corn or soybeans may also help reduce the effects of the disease.
What you really want to be on the lookout for is signs of early season development of SDS symptoms on the leaves. Susceptible varieties can “break” or collapse under high disease load, sometimes in conjunction with high SCN levels, and really produce poor yields. When fields do this, there usually are pockets where plants begin to show really poor growth and development before the majority of the field does. It is important to identify these areas early enough to put a plan in place before major yield losses can occur.