What Are the Spots on a Wax Myrtle?

Preventive Care

• Give wax myrtles the consistent care they need to grow strong. Healthy development increases a plant's ability to avoid and recover from problems, such as disease. Grow wax myrtles in areas that get full sun to partial shade. For best growth, maintain well-draining, slightly acidic soil -- these plants will thrive in nearly any condition other than extremely alkaline soils. Plant wax myrtles that thrive in your region for a successful experience. For example, Southern wax myrtles grow in U.S. Department of Agriculture plant hardiness zones 7b through 11 while Pacific wax myrtles grow best in USDA zones 7 through 9.

Diseases

• A fungal infection called anthracnose is likely to blame for the spots on your wax myrtle leaves. Caused by a variety of fungal pathogens, this disease thrives in cool, wet conditions, often appearing after spring rains. The disease spreads sporadically, carried on wind, rain or other splashing water, and targets twigs and leaves. While mature plants typically resist anthracnose infection and dry, warm conditions will greatly decrease the likelihood of development, the disease will flourish when conditions are favorable.

Effects

• Anthracnose disease begins with the appearance of spots on wax myrtle leaves. Spots may appear dark and look as though they are saturated with water. They often have a light brown to black color and the tissue within the spot may die. Immature leaves may die or become malformed while older leaves typically become covered with spots and areas of dying plant tissue. All the leaves may drop off your wax myrtle. In severe cases, damage includes branch dieback and distorted branches.

Control

• Optimal care is often all your wax myrtle needs to avoid infection. There is no cure or effective treatment for an existing disease, so resist the desire to apply chemicals. You may prevent reinfection by removing and destroying all fallen plant parts. In addition, maintain an open plant and prune away and destroy heavily infected plant parts to decrease disease and improve circulation. Prune during fall or winter, if possible, suggests University of California Statewide Integrated Pest Management Program. Water the soil directly rather than using overhead watering, which results in wet leaves and ideal conditions for the development of fungi.