What pests and diseases affect Welsh onions? Common types explained in one article
What pests and diseases affect Welsh onions? How should they be controlled? Please explain. The control of Welsh onion pests and diseases should be based on prevention, implementing a 2-3 year rotation with crops other than Allium species; cleaning the field to eliminate sources of pests and diseases; selecting disease-resistant varieties; disinfecting seeds, that is, before sowing soak the seeds in 50°C warm water for 25 minutes while stirring constantly, then soak...
What pests and diseases affect Welsh onions? How should they be controlled? Please explain
The control of Welsh onion pests and diseases should be based on prevention, implementing a 2-3 year rotation with crops other than Allium species; cleaning the field to eliminate sources of pests and diseases; selecting disease-resistant varieties; disinfecting seeds, that is, before sowing soak the seeds in 50°C warm water for 25 minutes while stirring constantly, then soak them in cold water, remove them, dry them and sow; applying sufficient base fertilizer, strengthening field management, and cultivating vigorous Welsh onions to enhance disease resistance.
1. Downy mildew. It mainly harms leaves and flower stalks. On flower stalks, yellow-white or milky-yellow, spindle-shaped or oval infection spots first appear, on which white mold develops, later turning pale yellow or dark purple. When middle and lower leaves are infected, the leaves above the diseased part gradually dry up and droop. When the pseudostem is infected, it mostly splits and bends. When the bulb is infected, it can cause the diseased plant to become stunted and the leaves to become deformed or twisted. When humidity is high, a large amount of white mold grows on the surface.
Control method: In the early stage of the disease, spray 75% chlorothalonil wettable powder at 600 times dilution, or 50% copper metalaxyl wettable powder at 800-1000 times dilution, or 64% sandofan wettable powder at 500 times dilution, spraying once every 7-10 days for 2-3 consecutive treatments.
2. Rust. It mainly harms leaves, flower stalks and green stem parts. In the early stage of the disease, slightly raised orange-yellow oval pustules appear on the epidermis, after which the epidermis ruptures and turns outward, releasing orange-yellow powder.
Control method: In the early stage of the disease, spray 15% triadimefon wettable powder at 2000-2500 times dilution, or 50% carboxin emulsifiable concentrate at 700-800 times dilution, or 70% mancozeb at 1000 times dilution plus 15% triadimefon at 2000 times dilution, applying once every 10 days for 2-3 consecutive treatments.
3. Sclerotinia rot. It harms leaves and flower stalks, and mostly occurs near the soil surface. The hyphae spread from the outer to the inner leaf sheaths; in severe cases the whole plant collapses, and the base rots and the plant dies. The diseased part produces white cottony hyphae and black short rod-shaped or granular sclerotia.
Control method: In the early stage of the disease, use 50% carbendazim wettable powder at 300 times dilution, or 50% thiophanate-methyl at 500 times dilution, or 40% dimethachlon at 1000-1500 times dilution to spray and drench the base of the plants, once every 7-10 days, for 2-3 consecutive sprays.
4. Allium leafminer. The larvae spend their entire lives tunneling in winding paths within the leaves, mining the leaf mesophyll, and winding tunnels can be seen in the leaves. When the mesophyll is damaged, only the upper and lower layers of white transparent epidermis remain; in severe cases the leaves wither.
Control method: During the peak occurrence period of adults, spray methomyl, or a mixture of 1000-1500 times dilution of methomyl emulsifiable concentrate plus 1000 times dilution of cypermethrin. Spray once every 5-7 days, for a total of 2-3 sprays. It can also control pests such as onion thrips.
Click to get more Welsh onion cultivation techniques
Click to get more vegetable cultivation techniques