Cotton Root Rot

The leaves on your plants, trees, and shrubs change color for many different reasons. Lack of water, too much water, not enough light, temperature, plant nutrition, and plant disease all affect the color of your leaves. The important thing is to be able to identify the reason behind the color change. Take notice on how many leaves are changing color, the condition that your plant is in, and how rapidly the changes happen. We are going to talk about a plant disease that changes the composition of your plants rapidly. Three days to be exact.

Whereas Rosette Rose Disease only affected variations of roses, Cotton Root Rot can affect over 2,000 species of plants. What is Cotton Root Rot? It is also known as Texas Root Rot, it is a plant disease caused by a fungus known as Phymatotrichum omnivorum. The fungus attacks the roots of the plant, killing them one at a time.  This causes the plants’ health to decline, eventually killing the once healthy plant. It spreads from plant to plant through the soil as root systems grow.

Photo from Neil Sperry explaining Root Rot click photo for link


Symptoms are most likely to show from June to September here in North Texas.  When our soil temperatures reach 83 degrees Fahrenheit.  The fungus thrives in our calcareous clay soils and can be found from Dallas to the Rio Grande. Cotton Root Rot often affects fruit trees, nut trees, ornamental plants, and shade trees. Knowing the symptoms and what to look for is imperative in controlling the fungus.

The leaves on the affected plants start to wilt and turn from green to yellow or brown. Typically the wilting starts at the upper most portion of the plant and works its way down. The plant is typically dead within 3 days of first showing signs of wilting. Plants can start to wilt in large patches but that is not always the case. After the plant has died they are usually easy to remove and cottony-like fungus is found on the roots of the plant.


Unfortunately, like RDD there is no cure for cotton root rot. There are ways to treat it but no cure at the present time.  To start treating for cotton root rot prune back your tree or shrub.  Then proceed to work ammonium sulfate into the soil surrounding the root system of your plant. You can only do this twice a year and make sure to water your plants thoroughly after treatment.


Since we live in an area that cotton root rot thrives, the best plan is to get ahead of it.  The best prevention is to work a fertilizer that is high in nitrogen into your soil surrounding your plants.  The fungus can live as deep as your roots will grow so it is important to treat all affected soil.

While Cotton Root Rot can be prevelent anywhere, those most often affected are  farmers. IF you suspect that your plants are affected you may want to uproot them and treat your soil prior to replanting.  It is important to get your soil tested every year or so at your local extention office.  Cotton Root Rot grows best in a soil PH of 7.0 to 8.5.

If you’d like to learn more about Cotton Root Rot click here for a PDF from the Texas A&M Extention office.
For a list of resistant plants to Cotton Root Rot click here. This is also put out by Texas A&M after many years of research.


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