Lagerstroemia is one of the ideal tree species for urban greening. However, once it has been invaded by pests and diseases, it will reduce its ornamental value. Now the common diseases and insect pests of crape myrtle are listed: First, crape myrtle powdery mildew Powdery mildew mainly invaded the leaves of crape myrtle, and the young leaves were more susceptible than the old leaves. Young shoots and buds can also be infected. White patches appeared on the leaves and expanded to form round patches. In severe cases, the entire leaf is yellow, causing early defoliation. The temperature is at 19-25°C and relative humidity is 100%. The disease is most likely to occur. It occurs mainly in spring and autumn, especially in autumn. The pathogenic bacteria are mycelium in the bud or The overwintering of the closed capsule shell on the deciduous leaf is transmitted by the air flow and can be invaded many times in the growing season. After the occurrence of powdery mildew, the intensity of photosynthesis decreased by more than half, the transpiration intensity of diseased leaves increased, and accelerated leaf senescence and death. Control methods: 1, strengthen the fertilization, pay attention to drainage in order to avoid excessive humidity; 2, reduce the source of infection, combined with autumn and winter pruning, elimination of diseased branches and concentrated burned, the growing season attention to timely removal of disease buds, diseased leaves and diseased shoots. 3, the incidence of plants can be sprayed 25% triadimefon WP 3000 times, or 70% thiophanate-methyl WP 1000 times, or 80% dexamethasone WP 500 times, the effect of alternate use of several agents Better. Second, Lagerstroemia Also known as the pomegranate carpet, it takes 2 generations in 1 year and winters as eggs or nymphs. The adult females and nymphs invade buds, leaves and shoots and cause harm to the sap, resulting in black foliage, leaves off, seriously affecting the growth and development of trees, and their excrement can induce coal pollution, which is one of the major insect pests harming crape myrtle. Control methods: 1. Strengthen quarantine to prevent pathogens from influx, rational fertilization, enhance plant resistance to insects, maintain ventilation, light transmission, avoid excessive plant density, combined with winter, early spring pruning concentrated pests. Hours, manual scraping. 2. Chemical control. (1) In the winter, spray 10-15 times of rosin mixture or 40-50 times of oil emulsion 1-3 times to eliminate overwintering females. (2) Before germination, spray 3-5 degrees lime sulfur or 3-5% diesel emulsion to eliminate overwintering nymphs. (3) The nymphs are the key to prevention and control. First of all, the newly hatched nymphs are sprayed with 500% SCV wettable powder 500 times or 5% phoxim EC 1000 times in the early spring. Grasp the key period when the shell has not been thickened during the incubation period and the drug is easy to penetrate. Spray once every 7-10 days for 2-3 times in a row. Use 40% omethoate emulsion, 80% dichlorvos emulsion, 50% thioxanthine Phosphorus EC, 25% imidophos emulsion 1000-1500 liquid spray evenly. 3. The use of polymer membrane spray mixture, sprayed on the plant to form a layer of film, so that the death of worms suffocating worms and the use of natural enemies, red-label lip predation can receive good results. Third, the crape myrtle In the north of China, 5-8 generations occur every year. The eggs are used for wintering near the shoots and shoots. May is the initial stage of disease. In June, the nymphs and adult clusters damage young leaves and suck juice, which affects the growth and development. Control methods: 1. In the early spring, the old bark was scraped and the damaged branches were burned and burned to eliminate the overwintering eggs. 2, strengthen the cultivation and management measures to reduce the source of the disease. 3, when the amount of aphids is large, cough 40% omethoate, 40% acephate 1000-1500 times or sprayed rattan fine 1000-2000 times, but pay attention to avoid phytotoxicity. 4. Artificial breeding and dispersal of natural enemies where conditions permit, such as: Harmonia axyridis and grass ridge larvae. 5. Using swatches to trap and kill, sticky winged aphids or white tin foils to reflect light and refuse to move and move aphids.