What if there is a small white cotton bud on the back of the mosaic?

1, powdery mildew

When the disease occurs, a layer of powdery substance appears on the leaves, branches and buds of trees, which affects photosynthesis, leading to uneven leaves, atrophy and dryness, abnormal new buds, and even serious plant death. Lagerstroemia indica and Acer truncatum are more common.

Powdery mildew overwinters with hyphae on diseased buds, diseased branches or fallen leaves. When the temperature is suitable in spring, it grows and develops, producing conidia for transmission and infection. From June to August, a large number of conidia were produced when exposed to high temperature, and the conidia were infected again after expansion. Conidia fall on leaves, germinate to produce hyphae, grow on the surface of leaves, and grow sucking cells to insert into tissues from stomata of leaves and absorb nutrients from leaves.

Knowing the occurrence regularity and infection process of powdery mildew, we can take the following measures to prevent and control it:

(1) Place the bonsai in a ventilated and light-transmitting environment. Reduce the density of bonsai and trim the branches and leaves appropriately;

(2) artificially reducing the ambient temperature and humidity;

(3) cutting off diseased branches and leaves, and centrally burning diseased branches and leaves;

(4) Spray protection. Before germination in early spring, the lime-sulfur mixture with Baume degree of 3~4 degrees is sprayed. If powdery mildew is found in the growing season, fungicides should be sprayed in time. ① 50% mancozeb 1000 times solution can be selected; ②70% thiophanate-methyl wettable powder 700~ 1000 times; ③ 800 times solution of 50% carbendazim wettable powder; ④25% triadimefon EC 1500 times.

I hope my answer is helpful to you!