Symptom Identification and Control Methods of Licorice Rust

Latin scientific name: Uromyces glycyrrhizae Magn.

Crops affected: Licorice

Symptoms: Mainly affects leaves. After seedlings emerge in spring, round, grayish-white small blister spots appear on the underside of leaves, and later the surface ruptures to reveal yellow-brown powdery masses, which are the pathogen's uredinia and urediniospores. In the late stage of the disease, the entire leaf is covered by uredinia, causing the aboveground part of the plant to die; the phloem tissue at the junction of the stem base with the root or stem proliferates, latent buds sprout, and the plant becomes clustered and dwarfed. After reinfection by urediniospores, dark brown telia are scattered on both sides of the leaves, and dark brown teliospore powder is released. This disease is the main disease of cultivated licorice, occurring throughout all major licorice production areas, and is the main factor affecting close planting.

Taxonomic attributes: Basidiomycota, Uromyces fungus

Distribution area: All major licorice production areas

Disease characteristics: The pathogen is a single-host parasitic rust fungus, overwintering as mycelium and teliospores on the plant's roots, rhizomes and dead aboveground branches, and producing urediniospores the following spring. The incidence of the disease is higher in cultivated licorice than in wild licorice. If the previous autumn is rainy and the temperature rises quickly the following spring, it is favorable for its occurrence. In Yikezhao League, the peak period of urediniospore-infected plants in two-year-old cultivated licorice is in mid-May, with an infected plant rate of about 10%; late June is the peak period of death of infected plants, with a mortality rate of over 90%. The peak period of teliospore-infected plants is in mid-July.

Control methods: After harvest, thoroughly remove diseased plant residues from the field. Select uninfected, robustly growing plants for seed; irrigate in winter and spring, and cut off the aboveground stems and leaves at the appropriate time in autumn to reduce the occurrence of the disease. In early spring, spray 20% Fenxiuning 1500-fold solution or 97% Dixesodium 300-fold solution 2-3 times.

Common pesticides: 20% Fenxiuning