What is Cotton Root Rot and How Does It Impact North Texas Trees?
Less than a century ago, the Dallas-Fort Worth area, was primarily agricultural land. This land was used to grow crops, hay, and raising cattle. The native tree species were much more limited. Now the land is used much differently. The old family farms are being developed into new shopping centers, homes, and other urban developments. The land use has changed and so has the landscape.
The DFW has added many new plant species to the pallet. As a landscape industry, we have integrated many plant species that have adapted to our area and climate. Some species were more successful than others. After many years of trial and error, plant diseases have found many suitable host species.
Photo 1: Fungal Mat ‘Phymatotrichopsis omnivora’
Photo 2: First Signs of Wilting
As new plant species were brought into our area, plant pathogens, whether native or not, have found their way in to our landscape as well. One disease that has over 2,300 host species (1,800 dicots), is known as, ‘Phymatotrichopsis omnivora’ (also referred to as, Cotton Root Rot, Texas Root Rot and Ozonia Root Rot). This is a soilborne fungus that lay dormant in the soil for many years.
As you may guess, cotton, a common crop that is grown in North Texas is very susceptible to this disease. Trees that are infected with Cotton Root Rot should be removed and only planted with tolerant or resistant plant species. Here’s a link to an online publication from Texas A&M University of Tolerant Plant Species: https://aggiehorticulture.tamu.edu/archives/parsons/publications/cottonrootrot/cotton.html
Diagnosis is very easy during the early and mid-summer. As the soil temperature exceeds 82 degrees, Fahrenheit, which is usually in the spring and early summer, the disease will develop in the plant. The first symptoms are wilting, followed by death. Often smaller plants are quickly killed by this disease. While larger trees may require more time for the disease to terminate the tree.
As a diagnostician, we are looking for key symptoms and signs out in the field. Common species, like Lace Bark Elms are very commonly killed by this disease. During the early summer, we look for fungal mats that develop on top of the soil as a key indicator that the pathogen is present. It has been demonstrated in research that the fungal mat does not spread the spores, so don’t worry about spreading this pathogen if you walk through a fungal mat or two.