Fungus on Texas Sage
Texas sage (Leucophyllum frutescens) is also commonly referred to as ceniza, barometer bush or purple sage. It is an evergreen shrub native to Texas and New Mexico. It is a hardy plant, particularly under the high heat conditions of its native land. Generally, these plants are low-maintenance and pest- and disease-free. There is only one type of fungus, cotton root rot, that affects the Texas sage.
Texas sage is hardy in USDA zones 8 through 11 and is incredibly heat-tolerant. It can grow up to 8 feet tall. It prefers full sun and rocky, alkaline soil. The leaves are oval and alternate on the stem. It flowers profusely, with tubular flowers that are up to 1 inch wide. Flower color depends on the cultivar but can be white, pink or purple with spotted throats. It flowers all summer and into fall due to the high humidity of the region. Established plants only require watering every two to three weeks in the summer.
It can be used as a hedge or border of mass plantings for screens. It grows well in Florida’s summer heat and is one of the most popular shrubs in southern Arizona. The Texas sage provides the backdrop for many desert gardens.
Cotton Root Rot
Cotton root rot is caused by the soil-borne fungus Phymatotrichopsis omnivora. It is also known as Texas root rot and Ozonium root rot. It is a very destructive disease but since it prefers summers with very high heat, it is limited mostly to the southwestern United States. It can attack more than 2,000 species of plants.
Symptoms of Cotton Root Rot
The first symptoms of infection include the yellowing of the leaves followed by the wilting of the plant. These symptoms start to occur in June when the soil temperatures reach 82 degrees Fahrenheit. The plant will die suddenly after the wilting, even if it was growing well prior to infection. Larger shrubs and trees die more slowly. By the time the outward symptoms have appeared, the roots have already been invaded by the fungus. Rotted roots are decayed, and wooly strands of the fungus can be seen. If the soil remains too wet, the spore mats, or spots of the fungus, can be seen on the top of the soil. They are white, cottony spots that later become tan and powdery. The fungus spreads by slowly growing through the soil from plant to plant. It can survive for many years.
There are several control methods for this fungus. One method is to add organic amendment to the soil. Another method is using plant barriers—planting resistant species around the sage to limit the spread. Another control method is to plant the sage alone instead of in rows or hedges. Finally, fertilizer high in nitrogen can disinfect the soil and reduce the incidence of root rot.