This white thing grows on the leaves of Lagerstroemia indica (1). Can I spray with the second medicine?

According to the picture, this is powdery mildew of Lagerstroemia indica.

Powdery mildew is a fungal disease, which mainly harms leaves. 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.

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.

The picture shows pesticides, which are ineffective against powdery mildew and need fungicides. Generally, 80% zineb wettable powder, 1000 times 70% thiophanate-methyl, 1500 times 20% triadimefon emulsifiable concentrate and 8000 times 50% carbendazim wettable powder can be sprayed.

I hope I can help you. Please adopt it if it is useful.