How to treat the pests and diseases of Lagerstroemia microphylla?

At present, powdery mildew is the main pest that seriously harms the growth of Lagerstroemia microphylla.

Powdery mildew mainly harms young tissues. At the early stage of the disease, there is a thick layer of white powder on the diseased buds and shoots, which affects leaf spreading and flowering. In the early stage of leaf infection, white mildew layer and irregular fading spots are produced on both sides of the leaf, and the severely damaged leaves shrink, fall off early or twist new shoots. At the early stage of the disease, the bud was born on the surface of powdery mildew layer and slightly faded spots, and the whole bud was seriously covered with white powder and could not bloom normally. When the flower organ is infected, white powder and irregular fading spots appear on the pink petals, and the flower organ wilts seriously and falls off early.

Pathogenic regularity: Pathogenic bacteria overwinter in dormant buds of diseased plants by mycelium. The conidia produced in the second spring spread through wind and rain, infecting new leaves and branches. The disease began in April and reached its peak in autumn, which led to the closure of capsules. After 10 months, the disease spread tends to stagnate. In rainy season or high humidity, it is easy to get sick, the plants are too dense, and the ventilation and light transmission are poor.

Preventive measures: (1) Prune in time to facilitate ventilation and light transmission. (2) Spraying Pomei 1 ~3 degree stone sulfur mixture in winter to inhibit the source of overwintering bacteria. (3) Spraying 20% triadimefon EC 1500 times solution at germination stage and bamboo shoot drawing stage of Lagerstroemia indica. In the areas with resistance to triadimefon, 30% Teflon EC or 12.5% myclobutanil 3000-3500 times solution and 40% Fuxing 7000 times solution can be used for prevention and control 2-3 times every 15 days.