Pecans are grand old trees that provide shade and a bountiful harvest of tasty nuts. They are desirable in yards and gardens, but they are susceptible to a number of diseases. Cotton root rot in pecan trees is a devastating disease and silent killer. If you have one or more pecan trees, be aware of this infection.
What is Pecan Cotton Root Rot?
Outside of Texas, when this infection strikes a pecan tree or other plant, Texas root rot is the more common name. In Texas it is called cotton root rot. It is one of the deadliest fungal infections — caused by Phymatortrichum omnivorum — that can strike any plant, affecting more than 2,000 species.
The fungus thrives in hot and moist weather, but it lives deep in the soil, and when and where it will attack plant roots is impossible to predict. Unfortunately, once you see aboveground signs of infection, it is too late and the plant will die quickly. The disease can attack young trees, but also older, established pecans.
Signs of Texas Root Rot of Pecan
The aboveground symptoms of root rot result from the roots being infected and unable to send water up to the rest of the tree. You’ll see the leaves turn yellow, and then the tree will die rapidly. The signs are usually first seen in summer once soil temperatures reach 82 degrees Fahrenheit (28 Celsius).
Pecans with cotton root rot will already show signs of serious infections below ground by the time you see wilting and yellowing in the leaves. The roots will be darkened and rotting, with tan, mycelia strands attached to them. If conditions are very wet, you may also see white mycelia on the soil around the tree.
What to Do about Pecan Texas Root Rot
There are no control measures that are effective against cotton root rot. Once you have a pecan tree succumb to the infection, there is nothing you can do to save it. What you can do is take measures to reduce the risk that you’ll see the fungal infection in your yard again in the future.
Replanting pecan trees where you already lost one or more to Texas root rot is not recommended. You should replant with trees or shrubs that resist this fungal infection. Examples include:
If you are considering planting a pecan tree in an area that may be susceptible to cotton root rot, you can amend the soil to reduce the risk that the infection will strike. Add organic material to the soil and take steps to lower the pH. The fungus tends to be more prevalent in soil at a pH of 7.0 to 8.5.
Texas root rot of pecan is a destructive disease. Unfortunately, research has not caught up to this disease and there is no way to treat it, so prevention and use of resistant plants in disease-prone areas is important.