Cotton Root Rot on Crape Myrtles


Crape myrtle trees are often grown as trees or shrubs within residential and commercial landscapes. As an ornamental plant, the tree produces pink, red or lavender flower clusters and is low-maintenance. It can be planted amongst a large variety of other plants, like altheas, but is susceptible to fungal diseases cotton root rot.

Crape Myrtle Trees

Crape myrtle trees prefer warm climates and are regularly found throughout the United States. They can reach a maximum height of 15 to 25 feet. Healthy growth in crape myrtle trees requires acidic, well-drained soil.


One of the first signs of disease are white spores from the fungal disease that will collect on the soil beneath diseased trees.When infected with cotton root rot, crape myrtle trees begin to loose color and moisture within the leaves. They begin to turn brown, remain attach to the tree and begin to die. The disease will spread amongst tree leaves until entire sections become wilted and dead. Cotton root rot also decays the root system of the tree and turns the infected roots molded and red.


The fungal disease caused by Phymatotrichopsis ominvorum is a hardy disease capable of survive cold winters and infecting more trees throughout the spring. Once temperatures begin to rise higher than 82 degrees Fahrenheit, the disease begins to spread rapidly. The infection will typically present symptoms of cotton root rot during the early summer. The symptoms will continue to develop and progress through June until September while weather conditions permit.


During the winter, the cotton root rot fungus will survive buried as deep as 8 feet beneath the soil. Throughout the winter the fungus will remain dormant, and then spread by wind, animals or pruning sheers. It is common for the same fungus to infect and reinfect the growth of a tree for years.


Cotton root rot spreads easily and is difficult to control. The main method of control is prevention of the disease in the first place. The fungus will grow faster in moist conditions, so gardeners must be careful to keep trees only moist enough to keep the tree healthy. Once infected, pruning infected leaves with sterilized sheers can prevent the spread of the disease. Also, adding green manure to the soil can reduce the spores present beneath the tree. Fungicides are not very effective against stopping the disease.

Keywords: Crape Myrtle troubleshooting, plant fungal disease, cotton root rot

About this Author

Jonathan Budzinski started his writing career in 2007. His work appears on websites such as eHow and WordGigs. Budzinski specializes in nonprofit topics, as he spent two years with Basic Rights Oregon and WomanSpace. He has received recognition as a Shining Star Talent Scholar in English while studying English at the University of Oregon.