What are the symptoms and effective prevention methods of powdery mildew of Lagerstroemia japonica?

Symptoms of powdery mildew of Lagerstroemia indica, a Japanese red leaf tree;

Powdery mildew is a worldwide disease with a wide range of hosts, and Lagerstroemia indica, a Japanese red-leaf tree, is an important target of its invasion. Powdery mildew of Lagerstroemia indica occurs in all provinces and cities where Lagerstroemia indica is planted in China. After the onset of Lagerstroemia indica, the leaves often turn yellow and fall off, which directly affects the tree potential and ornamental effect.

Symptoms: powdery mildew is a fungal disease, which mainly harms leaves, and young leaves are more susceptible to infection than old leaves; The disease also harms branches, shoots, buds and buds. At the early stage of the disease, small white speckles appeared on the leaves, and after expansion, they became round or irregular faded spots, covered with a layer of white powdery mildew, and the layer of white powdery mildew turned gray in the later stage. After the flowers are infected, the surface is covered with white powder, and the flower spikes are deformed, losing ornamental value. The plants affected by powdery mildew will become shorter, the tender leaves will be twisted and withered, the leaves will become smaller without spreading, and the branches will be deformed. If it is serious, the whole plant will die.

Occurrence regularity of powdery mildew of Lagerstroemia indica, a Japanese red leaf tree;

Occurrence regularity: Powdery mildew of Japanese red-leaf tree Lagerstroemia indica overwinters on diseased buds, diseased branches or fallen leaves. When the temperature is suitable in the next spring, the overwintering hyphae begin to grow and develop, producing a large number of conidia, which spread and infect with the airflow. The disease usually starts in April, gets worse in June, and gets worse in July and August.

It will slow down or stop because of the hot weather, but it may start again in September -65438+ 10. Powdery mildew occurs seriously in rainy season or under high relative humidity. Partial application of nitrogen fertilizer, too dense planting of plants or poor ventilation and light transmission are all beneficial to the disease.

Control methods of powdery mildew of Lagerstroemia indica, a Japanese red leaf tree;

① Horticultural control: Lagerstroemia speciosa, a Japanese red-leaf tree species, has strong germination ability. In winter, all the annual branches of seriously ill plants can be cut off and burned intensively to completely eliminate the source of the disease. If Lagerstroemia indica planted at home is found to be infected with powdery mildew, the diseased leaves should be removed in time and the potted flowers should be placed in a ventilated and light-transmitting place. Field cultivation should be well controlled.

Planting density, strengthening daily management, paying attention to increasing the application of phosphorus and potassium fertilizer, controlling the application amount of nitrogen fertilizer, and improving the disease resistance of plants.

(2) Chemical control: In areas with serious diseases, Bomei 3-4 degree stone sulfur mixture can be sprayed on branches before germination in spring; In the growing season, 80% zineb wettable powder can be sprayed 500 times, 70% thiophanate methyl 1000 times, 20% triadimefon EC 1500 times and 50 times triadimefon EC.

% carbendazim WP 8000 times solution. The above information is compiled by Jiangxi Sannong Hua Mu Garden Co., Ltd., hoping to help you!