What should I do if the crape myrtle tree grows black leaves? Treatment method is the key!
As the most dazzling flowering tree in summer, the sudden blackening of the leaves of crape myrtle trees has worried countless gardeners. This abnormal state may hide two completely different causes: false alarms of natural metabolism and a real crisis of fatal diseases. Only by mastering scientific identification methods and taking timely and correct measures can we protect this prosperous beauty of "a hundred days red" tree. Double analysis of the black leaf phenomenon of Lagerstroemia japonica trees The leaves of healthy Lagerstroemia japonica trees may show a natural dark brown gradient in autumn, which is a phenomenon of pigmentation when the leaves age. Through observation, it can be seen that only the old outer leaves change color, the vein texture is clear, and there is no sticky matter attached. No special treatment is required in such cases. Fatal crisis: Coal pollution infection characteristics When greasy black spots appear on new leaves and spread rapidly, and the leaves are accompanied by transparent mucus, coal pollution infection can be determined. The disease is caused by fungus breeding in aphids/scale insect excreta. The black spot area can expand by 30% within 24 hours. If not intervened in time, the entire plant will fall within three weeks. Physical blocking of the three-level control system for crape myrtle black leaves: spatial optimization technique keeps the plant spacing more than 2.5 meters, and ensures that the crown light transmittance reaches 60% after pruning. Inspect the eggs on the back of the leaves every week, and immediately wipe the infected branches with alcohol with scissors and cut them obliquely at 45° to remove them. Focus on cleaning up the aphid-gathering areas where the main trunk branches. Chemical prevention and control: Targeted treatment plan When the dew is dry in the morning, spray 10% imidacloprid 2000 times solution to kill insects, and then use a mixture of 75% chlorothalonil 800 times solution +0.1% washing powder to treat plaque 2 hours later. Severely ill plants require alternating use of difenoconazole and azoxystrobin twice a week for 3 weeks. Key points for year-round maintenance of crape myrtle trees are sprayed with stone sulfur mixture before germination in March every year, and phosphorus and potassium fertilizers are added every month from May to September to enhance resistance. Establish a pest and disease monitoring log to record daily temperature and humidity changes and pest dynamics. Combine it with planting insect repellent plants such as mint and rosemary to build an ecological protective barrier.
Through accurate identification of diseases and control of prevention and control timing, the black leaf problem of crape myrtle can be completely prevented and controlled. Remember: Prevention is better than treatment. Only by establishing a full-cycle maintenance system from soil improvement to crown management can this "summer emerald" remain vibrant forever.