Licorice Seed Processing Technology
Ringworm disease, also known as anthracnose, primarily affects the leaves and leaf sheaths of sorghum plants. The initial symptoms appear as small, red-brown, water-soaked spots that gradually expand in a concentric pattern, following the veins. These lesions turn yellow-brown to dark red, often forming semi-oval shapes along the leaf margins. They can vary in size and are typically marked by distinct ring-like lines, although some plant varieties may not show this feature clearly. Under high humidity conditions, reddish or purplish sticky substances—comprising fungal spores and mycelium—can be observed on the infected areas, along with black sclerotia. In severe cases, the lesions resemble leopard spots, leading to premature leaf death.
The pathogen responsible for this disease is *Gloeocercospora sorghi* (D. Bain & Edgerton), previously classified as *Dermatophyton sorghi*. It belongs to the subphylum Ascomycota. The conidiophores are multiple, solitary, colorless, and have 0–2 septa, measuring 6–20 × 1.5–2.5 µm. Conidia are produced in clusters within orange-red, viscous substrates, appearing linear, colorless, and slightly pointed at the tip. They lack visible septa and range from 32–112 × 3–4 µm. The disease typically occurs in July, and in rainy years, it spreads rapidly across large areas. Besides sorghum, it can also infect corn and sugarcane.
The pathogen overwinters in infected seeds or crop residues. During the next growing season, it can cause seedling death. On mature plants, large quantities of conidiospores are formed on lesions, which are dispersed through wind, leading to repeated infections and potential epidemics. There is significant variation in disease incidence among different sorghum varieties. High humidity, especially in low-lying fields, favors disease development and leads to early leaf death. In northern sorghum-producing regions, the disease tends to occur earlier, and cool temperatures combined with heavy rainfall in July and August can increase the risk of outbreaks, causing extensive damage.
To manage this disease, several control measures are recommended:
(1) Promptly remove and destroy diseased plant material after harvest, followed by deep plowing to bury the residue and reduce primary infection sources.
(2) Implement crop rotation and apply sufficient organic manure, along with balanced fertilization techniques. During field cultivation, top-dress with ammonium nitrate to avoid nutrient deficiency and improve plant resistance.
(3) Choose and promote locally adapted, disease-resistant sorghum varieties while eliminating susceptible ones.
(4) Treat seeds with 0.5% of the seed weight of 50% thiram powder, 50% carbendazim wettable powder, or 50% seed dressing double powder to protect against anthracnose and northern anthracnose during the seedling stage.
(5) In epidemic years or in highly susceptible fields, apply fungicides such as 36% Thiophanate-methyl suspension diluted 600 times, 50% carbendazim wettable powder diluted 800 times, 50% benomyl wettable powder diluted 1500 times, 25% carbon tetrachloride wettable powder diluted 500 times, or 80% Dasheng M-45 wettable powder diluted 600 times starting from the booting stage.
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