The main diseases of green onions include downy mildew, purple spot, rust, yellow dwarf, soft rot, gray mold, blight, white rot, anthracnose, leaf mold, black spot, etc.

(1) Downy mildew

The lesions on the leaves are oval or cylindrical, varying in size, light yellow-green, with unclear edges, and the diseased parts are white or light. Purple velvet mold. The leaves above the diseased area droop and dry up, and the pseudostems often bend toward the injured side and are easily broken.

Key points of prevention and control:

① Implement crop rotation with non-onion crops for 2 to 3 years.

② From the 5 to 6 leaf stage, spray 75% of chlorothalonil 600 times, 50% of dipendazim 500 times, or 1 to 2 mg/kg of cycloheximide once every 7 to 10 days. , 3 to 4 times in a row.

(2) Purple spot disease

The lesions mostly start from the middle of the leaf tips and can spread to the lower parts after a few days. In the early stage, the lesions are very small, slightly sunken, yellowish-brown to brown. When the humidity is high, the lesions are covered with brown to black powdery mildew-like substances, often arranged in concentric rings. The lesions often heal into large strip-shaped spots, causing the leaves to wither. .

Key points of prevention and control:

① Clean the fields and implement crop rotation for more than 2 years.

② Strengthen management, apply sufficient base fertilizer, reasonable top dressing, and drain water after rain to make the plants grow strong and strengthen disease resistance.

③Prevent and treat onion thrips promptly to avoid causing wounds.

④Spray 75% chlorothalonil wettable powder 500-600 times in the early stage of the disease, or 64 antiviral alum wettable powder 500 times, 58 metalaxyl manganese zinc wettable powder 500 times, every 7 seconds ~ Once every 10 days, control 3 to 4 times in a row.

(3) Rust disease

Occurs on leaves and green stems. In the early stage, there are oval or spindle-shaped slightly raised brown sores on the diseased parts. Later, they split vertically and the surrounding The epidermis turns up, exuding orange-yellow powder, and finally forms an oblong or spindle-shaped, dark brown, slightly raised lesion on the affected area. After the lesion ruptures, dark brown powder is exuded.

Key points of prevention and control:

①Select disease-free onion seedlings.

② In the early stage of the disease, remove the diseased leaves promptly and bury them deeply or burn them.

③Apply sufficient fertilizer, paying attention to the combination of nitrogen, phosphorus and potassium fertilizers.

④Spray 2000 times of 15 triadimefon wettable powder in the early stage of the disease, once every 7 to 10 days, and 2 to 3 times in a row.

(4) Yellow dwarf disease

The affected leaves produce yellow-green mottled or long yellow spots, the leaf surface is wrinkled and uneven, the leaf tube is deformed, and the leaf tips gradually turn yellow. Chlorosis and drooping, the growth of new leaves is inhibited, the plant is short, bushy or shrunken, and in severe cases the whole plant dies. The disease mostly occurs in the seedling stage. After the disease occurs, the seedlings grow slowly or stop, and cannot form green onion, seriously affecting the yield and quality.

Key points of prevention and control: ① Agricultural prevention and control: Choose healthy, virus-free seedlings and disease-resistant varieties; onion fields should not be adjacent to onion seedling or seed harvesting fields; strengthen fertilizer and water management to enhance plant disease resistance; check frequently In the field, remove diseased plants in a timely manner and bury or burn them intensively; disinfect hands and furniture that have come into contact with diseased plants, otherwise they cannot come into contact with healthy plants; pest control must be strengthened to reduce transmission routes; be careful not to damage onion seedlings during farming operations to avoid viruses Invasion from wounds.

②Pharmaceutical prevention and control: In the early stage of the disease, promptly spray 100 times the solution of 83 Anti-Virus Agent, 500 times the solution of 20 Virus A wettable powder, or 300 times the solution of Anti-Venom No. 1 aqueous solution.

(5) Green onion soft rot

Allium soft rot can harm the leaves, pedicels, etc. of green onions. At the initial onset, small, water-soaked, softened lesions appear along the veins on the first to second leaves. As the lesions expand to the base of the leaf sheath, the base of the leaf sheath becomes soft and rotten and emits a foul odor, and the outer leaves fall down.

Key points of prevention and control:

① Agricultural prevention and control: Choose varieties with strong disease resistance and stress resistance, and choose full, fresh, disease-free seeds; and non-onion and garlic crops Implement crop rotation for more than 2 years; clean the fields before planting and after harvest, remove dead branches, diseased remains, etc. from the field, and burn them or bury them deeply; cultivate strong seedlings and plant them at the right time to prevent high temperatures in the field; apply more organic fertilizer at the right time. Top dressing promotes plant growth and robustness, accelerates wound healing, and enhances disease resistance; strengthen water management, water lightly, drain water promptly during rainy seasons, and reduce field humidity; frequently check field conditions and remove diseased plants in a timely manner; strengthen pest control and pay attention to early stage Prevent and control underground pests, prevent and control various chewing mouthparts pests in the seedling stage, and reduce insect wounds.

②Pharmaceutical prevention and treatment: In the early stage of the disease, 4000 times of 72 agricultural streptomycin soluble powder, 4000 to 5000 times of neophytomycin, or 500 to 600 times of antibacterial agent 401 can be used. Or 77 Keshade wettable powder 500 times liquid, or 50 amber gum fertilizer copper acid acid wettable powder 500 times liquid, or 56 Kaoshan water dispersible microgranules 800 times liquid spray, spray once every 10 days, spray 2 times in a row . The above medicines should be used alternately.

③ Prevent and control storage diseases: Harvest on sunny days and fully dry in the sun to dry and harden the wound and accelerate healing; choose strong, disease-free, insect-free, and non-injured green onions for storage, and pay attention during storage Ventilate and maintain a low temperature of around 0℃.

(6) Gray mold

In the early stage of the disease, white spots appear on the green onion leaves, which are oval or nearly round, with a diameter of 1 to 3 mm, and mostly develop downward from the leaf tip. As the disease progresses, the lesions expand into one piece, until half or the entire leaf curls and dies, and the inner tissue of the leaf sheath rots. When it is humid, the disease will develop a gray mold layer.

Key points of prevention and control:

① Agricultural prevention and control: Choose varieties with strong disease resistance and stress resistance, and choose seeds with full, fresh and disease-free seeds, and non-onion and garlic varieties. Crops should be rotated for more than 2 years; diseased plants should be completely removed to reduce the source of bacteria in the field; plots with good drainage should be selected, and sorghum or ridge cultivation should be adopted, with reasonable dense planting to ensure good ventilation; water management should be strengthened to prevent large and small flooding, and planting should be done in a timely manner after rain Drainage to reduce field humidity; use formula fertilization and avoid over-application of nitrogen fertilizer to avoid excessive plant growth and reduce disease resistance; promptly remove diseased remains in the field after harvest, and then plow the soil deeply.

②Pharmaceutical prevention and control: In the early stage of the disease, use 1000 to 1500 times of liquid of 50 chlorine wettable powder, 2000 times of liquid of 50 sulfonate wettable powder, or 1000 times of liquid of 650,000 methamphetamine wettable powder. , or 50 times of Botrytis cinerea wet powder and 500 times of liquid spray. Choose any one of the above chemicals and use it in rotation, spraying once every 10 days or so, and spraying 2 to 3 times continuously.

(7) Diseases

Blights can damage leaves, pedicels, etc. When the leaves are affected, the initial stage is dark green water-soaked lesions, which expand into gray-white spots and surround the leaf body, causing the leaves to often break off from the diseased part and wither. When it rains continuously or the humidity is high, sparse white mold will appear on the disease. When the weather is dry, the white mold disappears, and cotton-like white mycelium can be seen when the skin is torn open. When the disease is severe, the diseased leaves rot and the entire plant dies.

Key points of prevention and control:

① Agricultural prevention and control: Choose varieties with strong stress and disease resistance, and choose seeds with full, fresh, disease-free seeds, and non-onion and garlic varieties. Vegetables should be rotated for more than 2 years; strong seedlings should be selected when planting, and diseased seedlings, weak seedlings and disabled seedlings should be eliminated; the fields should be thoroughly cleaned to remove diseased and disabled plants to reduce the source of bacteria in the field; select plots with good drainage and high and dry terrain for planting, and Use sorghum or ridge cultivation and reasonably dense planting to ensure good ventilation; strengthen water management and timely drainage after rain to reduce field humidity; use formula fertilization to promote healthy plant growth and enhance disease resistance; timely cultivating and weeding.

②Pharmaceutical control: First, seed treatment is carried out before sowing. Seed dressing can be carried out with 25% R. viridis equivalent to 0.3% of the seed weight.

Second, in the early stage of the disease, you can use 75% chlorothalonil wettable powder 500 times the solution, or 50% carbendazim wettable powder 500 times the solution, or 25% retinoic acid wettable powder 800 times the solution, or 64 antiviral alum wettable powder 500 times the solution. liquid, or 1500 to 2000 times liquid of 50 Soclin wettable powder, 500 times liquid of 58 Metalaxyl Manganese Zinc wettable powder, or 1000 to 1500 times liquid of 50 Phenhydrin wettable powder, or 72 Purik water 600 times liquid spray. The above agents should be used alternately, spraying once every 7 to 10 days and spraying 2 to 3 times continuously.

(8) White rot

It can occur in both the seedling stage and adult plants. When the seedlings are affected, the leaf tips turn yellow, and later the entire leaves turn gray-white and die, and finally the seedlings wither and die. When the disease occurs on an adult plant, the leaves turn yellow from the tip downwards and then die. The plant becomes dwarfed and withered, and the tissue at the base of the stem becomes soft. Later, it becomes dry-rotted, slightly sunken, gray-black, and extends upward along the base of the stem, and the underground part turns black. corruption. When the humidity is high, many downy white molds grow on the surface of the leaf sheaths or within the tissues, which later turn into gray-black, and a large number of black spherical sclerotia quickly form. The sclerotia are small in round shape and often overlap each other to form sclerotia blocks. The thickness of the sclerotia blocks can sometimes reach about 5 mm.

Key points of prevention and control:

① Agricultural prevention and control: Choose varieties with strong disease resistance or stress resistance, and choose seeds or disease-free onion seedlings with full, fresh, disease-free grains; Carry out crop rotation with non-onion and garlic vegetables for more than 2 years; choose plots with good drainage and dry terrain for planting; strengthen fertilizer and water management, drain water promptly after rain, and reduce field humidity; thoroughly clean the fields, remove diseased bodies, and reduce sources of bacteria in the fields; Strengthen field inspections, promptly burn or bury the removed plants together, and spread lime or plant ash on diseased plant holes to disinfect them; implement formula fertilization, do not apply nitrogen fertilizers in an unbiased manner, and apply more phosphorus and potassium fertilizers to enhance the plant's disease resistance.

②Pharmaceutical control: In addition to seed dressing with 50% carbendazim wettable powder equivalent to 0.3% in weight before sowing, use 500 times liquid of 50% carbendazim wettable powder or 70% A in the early stage of the disease. Irrigate the rhizomes or spray with 800 times liquid of basebutanine wettable powder, 1000-1500 times liquid of 50 times hydantoin wettable powder, or 800 times liquid of 68 times Deli wettable powder.

(9) Anthracnose

Anthracnose of green onions mostly occurs on leaves and pedicels. When the leaves are injured, nearly spindle-shaped or irregular light gray-brown to brown lesions with no edges will appear initially. Later, as the disease progresses, small black spots will appear scattered on the lesions, which are the conidia of the pathogen. When the disease is severe, the upper leaves die.

Key points of prevention and control:

① Agricultural prevention and control: Select disease-resistant varieties and leave seeds on disease-free or disease-free plants to prevent seeds from carrying bacteria; practice 2 with non-onion and garlic vegetables Rotate crops for more than one year; select plots with good drainage and high and dry terrain for planting, and plant them at a reasonable density to ensure good ventilation. When planting, select strong seedlings and eliminate diseased, disabled and weak seedlings; implement formula fertilization to enhance the plant's disease resistance; Strengthen water management, water appropriately, drain water promptly after rain, and reduce field humidity; clean fields thoroughly after harvest, check field conditions frequently, and remove diseased plants in a timely manner.

② Chemical control: Soak the seeds with 300 times liquid formalin for 3 hours before sowing, remove them, rinse them and dry them before sowing; in the early stage of the disease, use 75% chlorothalonil wettable powder 600 times liquid, or 80 times of anthrax thiamine wettable powder, or 70 generation mancozeb wettable powder, 500 times of liquid, or 64 antiviral alum wettable powder, 500 times of liquid, or 50 thiophanate methyl wettable powder, 500 times of liquid spray. Choose any one of the above-mentioned agents and use them alternately. Spray once every 10 days or so for prevention and treatment 1 to 2 times.

(10) Leaf mold

This disease damages the leaves. In the early stages of the disease, there are water-soaked chlorotic spots on the leaves. As the disease progresses, irregular dark green lesions of varying sizes and slightly depressions form. In the later stage, a dense black velvety mold layer grows on the lesions. When the disease is severe, the leaves dry up and die.

Key points of prevention and control:

① Agricultural prevention and control: Carry out crop rotation with non-onion and garlic vegetables for more than 2 years; choose plots with good drainage, fertile soil, and high and dry terrain for planting; when planting Select strong seedlings and eliminate diseased and weak seedlings; plant densely in a reasonable manner to maintain good ventilation and light transmission between plants; strengthen water management and timely drain water after rain to reduce field humidity; fertilize with formula to prevent plants from growing too long and enhance plant disease resistance; regularly Conduct field inspections and remove diseased plants in a timely manner; thoroughly clean fields after harvest to reduce sources of field pathogens.

②Pharmaceutical prevention and treatment: In the early stage of the disease, use 50 times of carbendazim wettable powder 500 times the liquid, or 40 times the sulfur suspension agent 500 times the solution, or 50 times the mixed sulfur suspension agent 500 times the solution, or 80 generations of Mancozeb wettable powder 600 times liquid, or 50 times benomyl wettable powder 1500 times liquid spray. Choose any one of the above agents and use them alternately. Spray once every 7 to 10 days and spray 2 to 3 times continuously.

(11) Black spot disease

Mainly damages leaves and pedicels. When the plant is injured, small water-soaked white spots initially appear. As the disease progresses, they turn into gray or light brown oval or spindle-shaped lesions that are slightly sunken. In the later stage, the lesions expand, often surrounded by yellow haloes and dark or black-gray mold-like substances arranged in concentric rings. When the disease is severe, the lesions may join together or expand around the leaf or pedicel, causing the leaf or pedicel to break, or the entire leaf to die.

Key points of prevention and control:

① Agricultural prevention and control: Select disease-resistant varieties and seeds with full, fresh, disease-free and pest-free seeds; implement crop rotation with non-onion and garlic vegetables for more than 2 years; Select well-drained plots for reasonably dense planting to allow ventilation and light transmission between plants; implement formula fertilization to prevent premature plant aging and improve plant disease resistance; irrigate properly and drain water promptly after rain to reduce field humidity; conduct regular field inspections and remove diseased plants in a timely manner ; After harvesting, thoroughly remove diseased residues from the field and bury them deeply or burn them.

②Pharmaceutical prevention and control: In the early stage of the disease, use 1500 times liquid of 50 chlorine wettable powder, 500 times liquid of 64 antiviral alum wettable powder, or 800 times liquid of 58 metalaxyl manganese zinc wettable powder. Or 75% chlorothalonil wettable powder 600 times liquid, or 70 generation mancozeb wettable powder 600 times liquid spray. Choose one of the above chemicals and use it alternately. Spray once every 10 days or so and spray 2 to 3 times continuously.