What are the disease prevention and control methods for licorice cultivation?

The main diseases of licorice are: rust, brown spot and powdery mildew. The prevention and control methods are as follows.    

1. Rust: when infected, yellowish-brown scar-like lesions appear on the underside of the leaves; after the epidermis ruptures, brown powder is released, which is the uredinium of the pathogen; in August-September, dark brown telia form, causing the leaves to turn yellow and wither, and in severe cases to fall off. Prevention and control methods: apply more phosphorus and potassium fertilizer to improve the disease resistance of the plants. Remove diseased plant residues and burn them in a centralized manner. In the early stage of the disease, spray with a 1000-fold dilution of 15% triadimefon, or a 400-fold dilution of 97% dinocap. 

2. Brown spot: it damages the leaves, and affected leaves develop round or irregular lesions. The lesion margins are brown and the centers are red, and grayish-black mold-like growth occurs on both the front and back of the lesions. Prevention and control methods: clear the garden in winter and dispose of diseased plant residues. In the early stage of the disease, spray with a 500-fold dilution of 65% mancozeb or 50% mancozeb, or a 1500-fold dilution of 70% thiophanate-methyl wettable powder, or a 1:1:100 Bordeaux mixture.  

3. Powdery mildew: affected leaves look as if a layer of white powder has been sprinkled on them, and later the leaves turn yellow, causing poor plant growth. Prevention and control methods: clear the garden and dispose of diseased plant residues; spray with a 1500-fold dilution of 70% thiophanate-methyl wettable powder, or an 800-1000-fold dilution of 15% triadimefon for prevention and control.