Rhizoctonia on row crops in the southern United States


An interview with Professor Rothrock of the University of Arkansas, United States (US).

Basel, Switzerland
September 9, 2014


Professor Rothrock

Professor Rothrock`s research focuses on the ecology of soilborne plant pathogens and their control through chemical, cultural and alternative strategies. It is directed towards the development of sustainable cropping systems for cotton and other field crops. One of his current research projects is the characterization of Rhizoctonia solani populations in Arkansas and their anastomosis groups, in soils under different cropping systems. We had the opportunity to speak with Professor Rothrock about the importance of Rhizoctonia in the southern United States and the findings of his research activities.

Video interview with Professor Rothrock


Why were you interested to start looking deeper into the occurrence of Rhizoctonia in the southern United States?

We have been dealing with a number of seedling diseases on several row crops, particularly cotton and soybean in the southern United States. Rhizoctonia is an important component of those seedling diseases and yet not much was known about the structure of those populations. The other Rhizoctonia disease with which we work is aerial blight on soybean. Because of the importance of Rhizoctonia as a plant pathogen in the southern United States, we wanted to get a view on how common Rhizoctonia was in the regional soils and what type of Rhizoctonia we could isolated of field crops.


What were your key findings?

One of the important facts is that we could find Rhizoctonia in almost every field soil we looked at. It is a very common pathogen and occurs frequently in the soils in the southern United States. The second aspect at which we had a closer look was what portion of the population was pathogenic and what anastomosis groups of Rhizoctonia were present. In this study, we could identify the major pathogens of the southern row crops which were cotton, soybean, rice, peanut and corn. In addition to that, we found that there were many nonpathogenic or parasitic Rhizoctonia present as well. We found that there is a large diversity of Rhizoctonia on our southern row crops.


What was the most frequent Rhizoctonia anastomosis group found over all crops?

The most frequently isolated Rhizoctonia solani AG that causes disease across the crops examined was AG4. This group is recognized as being important as a seedling disease on numerous crops.


Did you find differences between the crops?

Yes, we did. When we looked at cotton, we primarily isolated R. solani AG4, which is a seedling disease pathogen on that crop. On other crops, we isolated R. solani AG 2 and 4 which were also seedling diseases on those crops. In addition, we isolated R. solani AG11 – for which we don’t know if it is important in terms of disease on these crops. Overall, we found a variety of Rhizoctonia AG`s both pathogenic and nonpathogenic to these crops.


What is your take home message from this survey?

I think, for farmers, it is important to know that R. solani is frequently occurring in their soils and so they need to consider it when they are thinking of disease control options.


The second thing we discovered from our survey is that there are a lot of other Rhizoctonia present in our fields. We need to do more work on communities of Rhizoctonia and how they are functioning in our field crops.



Professor Rothrock was interviewed by Dr. Melanie Goll, Technical Innovation Manager, Syngenta. Melanie holds a Ph.D. in plant pathology and focuses on seed treatment development, especially fungicides and nematicides.