The Catawba Crape Myrtle (Lagerstroemia indica ‘Catawba’) is a popular landscape choice, known for its vibrant purple blooms and long flowering season. This deciduous tree or shrub offers multi-season appeal, with green foliage turning orange and red in fall, and attractive peeling bark providing winter interest. While resilient, Catawba Crape Myrtles can face challenges. Understanding these issues helps maintain plant health and beauty.
Common Diseases
Catawba Crape Myrtles can develop fungal diseases. Powdery mildew, caused by the fungus Erysiphe lagerstroemiae, appears as white to grayish patches on leaves, new shoots, and flowers. Infected parts may distort or stunt, and flowers might not open, though the disease is rarely fatal. It thrives in humid conditions with warm days, cool nights, and poor air circulation.
Cercospora leaf spot causes dark spots on leaves, often leading to premature leaf drop. It typically starts on lower leaves and spreads, with spores dispersed by wind, especially in late summer. Sooty mold, a black film on leaves and stems, is not a disease itself but a symptom of insect activity. It grows on honeydew, a sugary excretion from sap-sucking insects.
Pest Infestations
While generally pest-resistant, Catawba Crape Myrtles can attract certain insects. Aphids are small, soft-bodied insects that cluster on new growth, sucking plant sap. Their feeding distorts leaves and produces honeydew, which leads to sooty mold.
Crape myrtle bark scale appears as white, felt-like bumps, often in branch crotches. These scale insects also produce honeydew, causing sooty mold on trunks and foliage. Though rarely fatal, bark scale can stunt growth and reduce blooms. Japanese beetles are an occasional pest, skeletonizing leaves by eating tissue between veins, leaving a lace-like appearance.
Environmental and Cultural Stress
Environmental factors and improper care also stress Catawba Crape Myrtles. Inconsistent watering, whether too much or too little, affects plant health. Overwatering causes yellowing leaves, wilting, and root rot, especially in poorly draining soils. Underwatering leads to brown or crispy leaves, and prolonged drought can reduce blooming or cause plant death, particularly for new plants.
Crape Myrtles need 6 to 8 hours of direct sunlight daily for good growth and flowering; insufficient light results in sparse foliage and fewer blooms. Nutrient deficiencies cause yellowing leaves or poor growth. Improper planting, like planting too deep, hinders root development. Cold damage can also occur in colder winters, especially for young plants or unsuitable varieties, leading to dieback.
Solutions and Prevention
Sound cultural practices are the main defense. Plant in full sun (at least six hours daily) with well-drained soil. Good air circulation, achieved through proper spacing and pruning, reduces fungal diseases like powdery mildew and Cercospora leaf spot.
For mildew, choose resistant varieties; Catawba has some resistance. If diseases occur, apply fungicides as directed. Manage aphids and crape myrtle bark scale to prevent sooty mold. Horticultural oils, insecticidal soaps, or neem oil treat these pests. Systemic insecticides, applied as a soil drench, offer season-long control for bark scale and aphids, minimizing impact on beneficial insects.
Address environmental stresses by adjusting care. Water deeply and consistently, allowing soil to dry between waterings, especially during establishment and dry spells. Check soil moisture by hand. Fertilize in early spring with a balanced, slow-release fertilizer (e.g., 10-10-10) for healthy growth without excessive foliage.
Mulch around the base with a 2-3 inch layer to retain moisture, regulate temperature, and suppress weeds, keeping it a few inches from the trunk. For winter protection in colder zones, add extra mulch around the root zone and wrap young trees with burlap.