Symptom Identification and Control Methods of Ginger Eyespot Disease

[Pathogen scientific name] Drechslera spicifera (Bain) v. Arx

[Host crop] Ginger.

[Disease diagnosis] It damages leaves. When leaves are affected, small brown spots appear initially, and after expansion the lesions become spindle-shaped, 5-10 mm in size, grayish-white, with light brown edges and a distinct or indistinct yellow halo around them. When humidity is high, dark gray to black mold-like growth appears on both sides of the lesions. When the disease is severe, the lesions on the leaves merge into patches, causing the diseased plants to wither and die. The pathogenic fungus is Drechslera. The conidiophores of the pathogen are mostly solitary, straight and unbranched, olive-yellow, slightly lighter at the tip, with the basal cell swollen; the conidiogenous cells are mostly proliferating, with sympodial extension. The conidia are oblong-elliptical, with obtuse-rounded ends, straight, pale olive-yellow, and have 3-7 septa. The conidia are solitary or borne at the tip and sides.

[Occurrence pattern] The pathogen overwinters in the soil as conidial clusters on diseased plant residues and with them. The following year, the overwintering fungus produces conidia that infect and cause disease in field plants; diseased plants produce large numbers of conidia, which spread through wind and rain, causing re-infection, and the disease continuously expands and spreads. The pathogen favors warm and humid conditions, and warm, humid conditions are conducive to the occurrence and development of the disease. Low-lying, humid areas with insufficient fertilizer, especially insufficient potassium fertilizer, have severe disease. Extensive management and poor plant growth significantly worsen the disease.

[Control measures] (1) Choose fertile plots with higher terrain and good drainage for planting. Do a good job of plowing and land preparation. (2) Apply sufficient decomposed manure and increase the application of phosphorus and potassium fertilizers; especially potassium fertilizer must not be lacking. (3) Irrigate moderately, and after rain clear the ditches and drain waterlogging to reduce field humidity. (4) In the early stage of the disease, promptly pull out diseased plants or remove diseased leaves to reduce the source of inoculum in the field. After harvest, thoroughly remove diseased residues from the field, burn them in a centralized manner or bury them deeply, and then deep-plow the soil. (5) In the early stage of the disease, apply chemical control promptly. The chemicals can be selected from 30% copper oxychloride suspension concentrate at 600 times dilution, or 12% copper octanoate emulsifiable concentrate at 500 times dilution, or 30% Lvdebao suspension concentrate at 400 times dilution, or 77% Kocide wettable microgranule powder at 600 times dilution, or 50% Sumilex wettable powder at 1500 times dilution, or 40% Baishuangjing gel suspension concentrate at 600 times dilution.