Numerous people have made statements about the disease that at this point we are referring to as the “mystery disease”. In some cases since 2007 the disease has also been referred to as “black root rot”. However, the fungus that causes black root rot, Thielaviopsis basicola, has not been recovered from infected plant or root systems in MS.
For the 2015 season there are likely no management practices that can be implemented to reduce the potential yield loss that can be associated with the disease. However, research is currently underway at MSU, as well as at the University of Arkansas and LSU AgCenter, to determine the specific causal organism so that field-level trials can begin to determine the best method of combatting the disease. The work in MS was supported by the Mississippi Soybean Promotion Board.
Several steps are necessary in properly diagnosing/characterizing a plant disease:
- Collect plant tissue samples with the disease in question.
- Isolate the organism from the plant in the laboratory.
- Use general microbiological growth medium.
- If the organism is an obligate parasite and requires living plant material to grow then a growth medium will not work; however, if the organism will sporulate then tools can be used to isolate and collect the fungal fruiting structures for additional observation.
- Correctly identify the specific organism involved in causing the disease.
Also, as a bit of clarification, what is in a name can be confusing. Since the “mystery disease” was first observed (ca. 2006/2007, if not earlier) the disease has likely been referred to using several different names. Over the years:
-black root rot
-generalized root rot
At this point, even if we have isolated the causal organism the name will remain “mystery disease” until the greenhouse trials have been completed and we definitively determine the specific causal organism. With this in mind, before we can determine how to manage the disease the greenhouse trials as well as additional plant tissue sampling will be conducted throughout the 2015 season to determine the organism(s) involved and how we can best manage those.