Cercospora leaf spot is a common issue that can affect crape myrtle bushes or trees during hot summers with above-average rainfall. This fungal disease manifests as small spots on the leaves, causing them to turn red and drop prematurely from the plant. As a gardening and landscaping expert, I have encountered this problem numerous times and can provide some insight into why your red rocket crape myrtle leaves may be turning red.
1. Environmental conditions: Cercospora leaf spot tends to thrive in warm and humid environments. During hot summers, the combination of high temperatures and excess moisture creates ideal conditions for the fungus to grow and spread. If your region has experienced above-average rainfall, it could contribute to the development of this leaf spot.
2. Poor air circulation: Crape myrtle bushes or trees with dense foliage or those planted in crowded spaces may have limited air circulation. This lack of airflow prevents the leaves from drying quickly after rainfall or irrigation, creating a moist environment that encourages fungal growth. It’s essential to ensure proper spacing and pruning to allow for better air circulation.
3. Overhead watering: Watering the crape myrtle from above, especially during hot and humid conditions, can contribute to the spread of fungal diseases like Cercospora leaf spot. The splashing water can disperse spores onto the leaves, facilitating infection. Consider using drip irrigation or a soaker hose to water at the base of the plant, minimizing contact with the foliage.
4. Lack of sunlight: Crape myrtle bushes or trees require adequate sunlight to thrive. Insufficient sunlight can weaken the plant and make it more susceptible to diseases. If your crape myrtle is not receiving enough sunlight due to shading from nearby trees or structures, it may be more prone to developing leaf spot. Pruning nearby vegetation or transplanting the crape myrtle to a sunnier location can help alleviate this issue.
5. Plant stress: Stressed plants are more vulnerable to diseases, including Cercospora leaf spot. Stress can result from factors such as inadequate watering, nutrient deficiencies, or root damage. Ensure your crape myrtle is receiving sufficient water, appropriate fertilization, and proper care to maintain its overall health and resilience.
To manage and prevent Cercospora leaf spot:
– Prune the crape myrtle to improve air circulation and reduce foliage density.
– Avoid overhead watering and opt for drip irrigation or soaker hoses.
– Ensure the crape myrtle receives adequate sunlight by removing nearby shading vegetation or considering a relocation.
– Regularly inspect the plant for signs of disease and promptly remove infected leaves or branches.
– Apply a fungicide labeled for Cercospora leaf spot if the problem persists or worsens.
It is important to note that while Cercospora leaf spot can cause aesthetic damage to the crape myrtle, it generally does not pose a significant threat to the plant’s overall health and longevity. With proper management and care, your red rocket crape myrtle can recover and continue to thrive.
