Recently, many green onion growers have reported symptoms such as dry tips, white spots, and curved white tracts in the onion leaves. The preliminary diagnosis of the dry tip by the field was onion onion, the white spot was damaged by the onion thrips, and the curve-shaped white road was caused by the damage of the onion leaffly. It is recommended that the majority of onion farmers take precautions to prevent serious production losses. The major pests and diseases and control measures of welsh onion are described as follows:
The main diseases of green onions are downy mildew, purple spot, gray mold, and epidemic diseases; the main pests are the onion seed fly, onion leaf fly, onion thrips and so on.
1. Downy mildew. The disease mainly harms the leaves and pedicels of green onions. Generally low-lying, poorly drained, and heavily re-emerged, the weather is often cool and rainy or often has heavy fog. In the early days after infection, ovoid round yellow-white spots were produced on the leaves or pedicels, the edges were not obvious, the lesions expanded and jointed, and they developed tubularly along the leaves and stems, and turned into dead spots when dry. When the middle and lower parts of the leaves are injured, the leaves above the diseased part will droop. The pseudostem is susceptible, the disease is broken, and the plant is bent. Bulb disease, can cause systemic infection, dwarf diseased plants, distorted leaf blade, showing pale green, high humidity, the surface of white fluffy material, was dark gray mold layer. At the beginning of the disease, 75% of chlorothalonil wettable powder 600 times, 58% of metalaxyl manganese zinc 600 times or 64% of antiviral 500 times of spray, spraying once every 7-10 days, continuous control 2-3 Times.
2. Purple spot. The leaves and pedicels, which are mainly harmful to Welsh onion, can also damage the leaf sheath. The lesions are initially water-stained, with slight depressions. They then expand into elliptical or spindle-shaped, brownish or dark purple, and are often surrounded by yellow halos. Several lesions healed to grow a bar-shaped lesion. When wet, the diseased area produces dark brown or dark gray moldy layers in a concentric ring pattern. When the disease is heavy, leaves, stems die or fold. At the beginning of the disease, spray 75% chlorothalonil wettable powder 500-600 times, 75% mancozeb wettable powder 600 times or 64% antivirus 500 times, and spray once every 7-10 days for continuous prevention and treatment. 3-4 times.
3. Gray mold. Also known as white spot disease, is the main disease of green onions. The main damage to the leaves, the beginning of the white oval or near-round spots on the leaves, and more developed from the tip of the blade, and gradually even into pieces, so that the onion curled to death. When the humidity is high, a large amount of gray mold layer appears on the dead leaves. In the early stage of the disease, 50% carbendazim or 70% thiophanate-methyl wettable powder 800-1000 times was used to control the rotation.
4. Diseases. The main symptoms are diseased leaves and pedicels. The initial appearance of blue and white spots is not obvious, and grayish white spots appear after expansion, causing the leaves to wither. The field presents a “dry tipâ€. When the humidity is high, the diseased minister sparsely molds. When the weather is dry, the white mold disappears. The long tapering leaves inside the necropsy reveal white mycelium, which is different from onion physiological “dry tipâ€. ". At the beginning of the disease, spray 64% anti-virus WP 500 times fluid or 25% metalaxyl wettable powder 600 times, spray once every 7-10 days, and control 2-3 times in succession.
5. Onion flies. In spring and autumn, the pseudostem spawns near the ground, hatching larvae (green onions) dive into the base of the leaf sheath, and eat young leaves and growing points. Some larvae break into the onion bulbs, causing rot, yellow leaves, wilting, and even death. Remove the victim onion when planting. In adulthood, use 2.5% of deltamethrin EC 3000 times solution or 20% cypermethrin EC 2000 times solution, spray once every 7-10 days, and control 2-3 times.
6. Liriomyza. It is the main pest of the green onion leaves. The larvae feed into the tunnel in the leaf tissue, showing a curve or mess, destroying the green tissue of the onion leaves and affecting the growth of green onions. The larvae damage period can be controlled with 1.8% avermectin 3000 times solution or 18% insecticide double 600 times spray. Adults can be sprayed to kill and kill 4000 times liquid.
7. Green onion horses. 6-10 generations occurred in 1 year, and there were hazards from May to September, especially severe high temperature and dry weather in July and August. Adults and nymphs damage the heart and leaves of the host plant with a sucking mouthpart, causing the onion to form many long-shaped yellow and white markings. In severe cases, the onion leaves are distorted and brown. Can use 50% phoxim EC 1000 times spray, spray every 7-10 days, even spray 2-3 times.
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