What is the reason why the leaves of potted osmanthus trees do not stretch and gradually turn rusty from the tip to the fallen leaves?

Osmanthus rust: Rusts include black rust, white rust and brown rust. All of them are spread by pathogen spores, and it is easy to get sick when the climate is wet. It first appeared in early July, but became serious in September, especially on leaves. Black rust is one of the most common rust diseases. At first, pale spots appeared on the surface of leaves, which gradually expanded into slightly rounded protrusions. Soon, the epidermis of the back of the leaf broke, producing piles of orange powder, which was scattered with the wind and spread widely. Then dark black oval spots are produced on the leaves, and black powder is produced after the epidermis of the back of the leaves breaks. In severe cases, the whole plant is infected from bottom to top, resulting in dry leaves. Gray-white circular spots appeared on the surface of white rust leaves, which gradually turned reddish brown and finally turned black brown. In severe cases, plants will die, which is more harmful than black rust. Brown rust leaves are covered with light brown or orange spots, which make the leaves yellow.

Control method: spray 80% mancozeb 50O times solution, 25% fenxiuning wettable powder 1500 times solution, 20% weixiuling EC 4o times solution, 25% metalaxyl wettable powder 800 times solution, 5% metalaxyl wettable powder 6o times solution or.

500 times of 75% chlorothalonil wettable powder, sprayed once every 7- 10 days, used alternately for 3-4 times, can achieve good control effect.