What are the control methods for licorice rust disease?

① Pathogen The pathogen of licorice rust (Uromyces glycyrrhizae) belongs to Basidiomycota → Teliomycetes → Uredinales → Pucciniaceae → the genus Uromyces.

② Disease pattern

a. Urediniospore stage In the seedling stage of licorice, infected plants show a light brown uredinium at the tip of leaves that have not yet unfolded. As the young leaves flatten and grow, the spore masses appear densely along the leaf tip and the underside of the leaf, and finally the entire underside of the leaf is covered by spore masses, appearing as a sheet of yellow rust color; generally all leaves of the whole plant become diseased, and diseased plants are noticeably dwarfed.

b. Teliospore stage The telial masses are dark brown, darker in color than the uredinial masses, and the spore masses are not continuous, distributed sparsely and scattered on the underside of the leaf, but both the diseased plant rate and the diseased leaf rate are high, and there seems to be little effect on plant growth.

For cultivated licorice, the initial, peak and late stages of uredinial diseased plants occurred in early, mid and late July respectively, and the peak stage of telial diseased plants was about 70 days after the peak stage of uredinial diseased plants.

③ Damage situation For any plant infected with urediniospores, the mortality rate of diseased plants is very high, reaching more than 98%, and it causes death of roots and rhizomes, affecting harvest yield. Telial diseased plants occur relatively commonly, but the plants will not die from the disease, which is completely different from the damage of uredinial diseased plants.

④ Control Strengthen field surveys, and promptly remove uredinial diseased plants when found to prevent spread; irrigation in winter and spring, and timely harvesting of aboveground stems and leaves in autumn can reduce the occurrence of the disease; treatment with triadimefon and Nongkang 120 showed extremely significant control effects on licorice rust diseased plants at the uredinial stage, with relative control efficacy both reaching more than 71.2%.