The crape myrtle is an extremely popular shrub because of its dark green leaves and beautiful flowers. It is versatile enough to be grown as a shrub or tree, thriving in moist, well-drained soils that receive full sun. Despite their relative ease of care, crape myrtles can be susceptible to a couple of diseases. The two diseases that most commonly affect crape myrtle plants are powdery mildew and leaf spot, both of which can be very damaging to the plant. Read below for more information on the two most common crape myrtle diseases.
The most common disease in crape myrtles is powdery mildew. It is a fungus produces white patches on the crape myrtle's leaves, shoots and flowers. In plants that get hit hard by powdery mildew, twisting of leaves and dropping of flowers can occur. These symptoms are more likely to occur on shrubs than trees, although it is not impossible for powdery mildew to devastate the latter form of the plant.
The mildew generally appears in summer, but it can hit plants as early as April in some regions. The mildew intensifies as the summer progresses. Warm, dry weather increases the likelihood of your crape myrtle getting attacked by powdery mildew or a current case worsening. One of the reasons powdery mildew can be difficult to remove is that it does not die during winter. Instead, it becomes dormant in the form of mycelia, hiding in leaf buds.
Cercospora leaf spot is the second major disease which affects crape myrtles. Like powdery mildew, it is a fungus, but not as widely known. It causes discoloration of crape myrtle leaves (usually to red or yellow) and even defoliation. It first appears on leaves as very small, irregular brown dots. The spots begin to grow in size and quantity, and the plant's leaves start to twist. Symptoms appear in mid-summer, but defoliation and discoloration do not happen until fall.