Symptoms and Control Methods of Licorice Root Rot

Latin scientific name: Rhizoctonia solani Kuhn

Damage symptoms: Infected plants develop yellowed, withered leaves; the stem base and main root all turn reddish-brown and dry-rotted, with longitudinal cracks or red streaks on them; lateral roots are rotted or very few; diseased plants are easily pulled out of the soil; the vascular bundles of the main root turn brown; when humidity is high, pink mold grows on the roots.

Morphological characteristics of the pathogen: generally caused by nematodes and Pythium species.

Classification: called Rhizoctonia solani, a fungus of the subphylum Deuteromycotina

Disease occurrence characteristics: Fusarium is a soil-inhabiting fungus that lives saprophytically in the soil for a long time. The pathogen spreads through water flow and cultivation, and invades through root wounds or directly through cracks at branching roots and openings at the stem base of aging seedlings. Damage by underground pests and nematodes creates wounds that facilitate pathogen invasion. Plots with extensive management, poor ventilation, and trapped moisture are prone to the disease.

Control methods: 1. Control soil temperature and prevent moisture retention. 2. Practice crop rotation, and use drilling or high-ridge cultivation. 3. Prevent wounds to seedlings during storage, transport and transplanting. Pay attention to controlling underground pests. 4. Soak seedlings for 5 minutes in a 200-fold dilution of a 1:1 mixture of 50% carbendazim and licrobic, then air-dry for 1-2 hours before transplanting; the control effect is high. 5. At the early stage of the disease, spray or drench with an 800-900-fold solution of 50% thiophanate-methyl or carbendazim wettable powder, or a 1500-fold solution of 50% benomyl wettable powder.

Commonly used agents: 50% carbendazim, licrobic, 50% thiophanate-methyl, 50% benomyl wettable powder