The leaves of my crape myrtle have become like this. What happened?

Powdery mildew of Lagerstroemia indica

Powdery mildew of Lagerstroemia indica is a common disease on Lagerstroemia indica, which is seriously harmful in some areas.

symptom

Powdery mildew of Lagerstroemia indica occurs on tender leaves and buds. In spring and summer, tender buds and leaves are distorted and covered with a layer of white powder after being infected. When the leaves are spread out, they will get sick. The diseased spots on the leaves are round and covered with white powder. In severe cases, they can also be connected together. The diseased leaves fall off in advance, which affects the growth. After the flowers are infected, the surface is covered with white powder, and the flower spikes are deformed, losing ornamental value.

cause of a disease

It belongs to Uncinula, Australia. Belonging to Sclerotinia sclerotiorum and powdery mildew. It grows on both sides of the leaf.

Transmission route

Powdery mildew of Lagerstroemia indica overwinters on the diseased body with mycelium, and conidia are produced in the following year, which is spread by wind and rain and infected. It usually starts in May and gets worse in June. It stops or is mild in hot weather from July to August, and becomes severe again in September-65438+10. The branches and leaves germinated at the lower part are seriously ill, and the site is seriously ill when it is wet, cold, sultry, poorly ventilated and transparent.

Prevention and cure method

1. Gardening has a strong ability to prevent Lagerstroemia indica from sprouting. In winter, seriously ill trees can cut off all the branches of the year, remove the diseased leaves and branches, and reduce infection. Family potted Lagerstroemia indica should remove the diseased leaves in time and put the potted flowers in a ventilated and light-transmitting place.

2. Chemical control from mid-May, spraying 500 times of 80% zineb wettable powder, 70% thiophanate-methyl 1000 times of solution, 20% triadimefon 4000 times of solution or 1% bordeaux solution every * *.

Of course, it is also possible that the scale insects of Lagerstroemia indica are harming Lagerstroemia indica, which is one of the important pests of Lagerstroemia indica. This kind of insect is dormant on the branches and sucks the juice, which is extremely harmful and needs to be controlled in time.