Drought tolerant and durable, mesquite trees (Prosopis spp.) are a blessing for gardeners in arid climates who want a hassle-free tree. Though adaptable, the mesquite tree is not immune to the effects of poor cultural conditions and may develop a fungal disease. An effective management strategy will incorporate changes to the tree's care routine.
Rust is a common disease that is easy to identify, as it causes dry masses or pustules of reddish, yellowish or orange spores to appear on the upper surfaces and undersides of leaves. Leaves may drop prematurely if heavily infected. Rust may also form cankers on bark, which eventually cause branch dieback. The University of California Integrated Pest Management Program recommends removing and destroying rust-infected leaves and pruning off any infected shoots and branches as they appear.
Ganoderma Root Rot
Ganoderma root rot is caused by a soil-borne fungus that enters the roots. Roots gradually rot, resulting in the decline and death of the tree. The most obvious symptom of the disease is white fruiting bodies appearing at the base of the tree. Eventually they may grow and turn reddish brown and glossy. They release spores, which may form a reddish brown dust in the nearby vicinity. The disease is not treatable, according to the University of Arizona. Prevent the disease by avoiding injury to the roots and the lower trunk.
Powdery mildew may infect mesquite trees, causing a grayish-white powder to appear on leaves. In severe cases, leaves may become distorted. Control is not generally necessary, though you can spray the foliage with a plant-based horticultural oil such as neem or jojoba oil to help remedy the problem. Follow the recommended rates on the label. You should not apply oil when temperatures are above 90 degrees Fahrenheit. Do not apply oil to water-stressed trees.
Texas A&M recommends no control measures for two other fungal diseases of mesquite, spongy yellow heart rot, which in advanced stages can turn the interior of the tree soft and spongy, leaf spot, which usually causes only limited damqge. Mesquite trees prefer bright, sunny conditions and well-draining soil. The honey mesquite (Prosopis glandulosa), common from Texas to California, is suitable for U.S. Department of Agriculture plant hardiness zones 6B to 9B, where it tolerates dry conditions once established. Water regularly when first planted to help the tree establish a healthy root system. Avoid overhead irrigation, as wet leaves favor fungal development. Water in the morning so that any splashed leaves will dry out before evening.