How to prevent and control Welsh onion dwarf disease? Detailed explanation of prevention and control methods
Prevention and control of Welsh onion dwarf disease
(Agricultural Wealth Network) The pathogen of Welsh onion dwarf disease is a virus, and it is one of the main diseases occurring on onion and garlic crops in recent years. Welsh onion dwarf disease, also called yellow dwarf disease, is the symptom shown by Welsh onions after virus infection. In recent years it has occurred commonly in onion fields in our city, especially in old vegetable-growing areas and Welsh onion production bases, and the disease has shown a trend of worsening. After onset, mild cases reduce yield by 20%-30%, and severe cases can reduce yield by about 75.
On onion bulbs it appears as yellow dwarf virus, on Chinese chives and garlic it appears as yellow stripe virus, and on green onions it appears as latent virus, etc. Newly planted onion seedlings grow well; if there is high temperature and drought in July, a few typical dwarf disease plants appear in August, and the peak incidence is from mid-September to mid-October. In the early stage of the disease, the new leaves produced are tender and thin, the leaf color becomes lighter, pale yellow spots appear on the heart leaves, the leaf surface is uneven, and the leaves twist spirally; some leaves twist to one side, the plant becomes stunted, and the onion plant grows smaller and smaller. According to field observations: old vegetable fields used for seedling raising and continuous cropping; early seedling raising before "Autumn Equinox" leads to more bolting the following spring; onion seedlings planted after being sun-dried until half dry; serious occurrence of thrips and aphids during the seedling stage; soil drought after planting and revival; years with high temperature in July and relatively little rainfall have more severe disease.
In view of the occurrence characteristics of Welsh onion dwarf disease, adopting comprehensive cultivation measures can greatly reduce the occurrence of this disease. (1) When raising seedlings, choose disease-resistant varieties such as Zhangqiu Dawutong, Wuyeqi and their first-generation hybrids, Luoyang Dongqing, Tangshan Dubai, etc.; (2) Change early seedling raising before "Autumn Equinox" to late seedling raising after "Autumn Equinox", and vigorously promote spring seedlings raised under plastic film mulching at "Spring Equinox"; (3) During the seedling stage, use a 1000-fold mixture of 40% dimethoate and 80% dichlorvos, adding a small amount of washing powder or waste soybean milk to increase adhesion (the following pesticide uses are the same), to control thrips and aphids; (4) Before planting onions, apply heavy base fertilizer, sort seedlings by grade, dip roots in 1000-fold dimethoate solution, and plant strong seedlings; (4) After planting and revival, spread wheat bran 250 kg/667 sq m or potato vines, fresh tender weeds 300 kg/667 sq m in the onion furrows to retain moisture and lower temperature, loosen soil and fertilize the field; (6) From August to October during the growing period, apply a special compound fertilizer for Welsh onions once at 50 kg/667 sq m, and apply urea 2 times at 20 kg/667 sq m each time. Coordinate topdressing with intertillage, hilling, and watering to promote strong seedling growth of Welsh onions; (7) Spray 2 times before planting onions, once every 7-10 days, and spray 3 times after planting with naphthalene acetic acid amine liquid, 1 vial diluted with 20 kg water, to prevent disease and strengthen plants; (8) If a small number of diseased plants still appear in the onion field, use 0.5% Kangbingsu No. 1 at 300-400 fold, or 25% Kangbingdu No. 1 wettable powder at 300 fold, or 1.5% Zhibingling at 400 fold for thorough control, ensuring strong growth and a bumper harvest of Welsh onions.
On onion bulbs it appears as yellow dwarf virus, on Chinese chives and garlic it appears as yellow stripe virus, and on green onions it appears as latent virus, etc. Newly planted onion seedlings grow well; if there is high temperature and drought in July, a few typical dwarf disease plants appear in August, and the peak incidence is from mid-September to mid-October. In the early stage of the disease, the new leaves produced are tender and thin, the leaf color becomes lighter, pale yellow spots appear on the heart leaves, the leaf surface is uneven, and the leaves twist spirally; some leaves twist to one side, the plant becomes stunted, and the onion plant grows smaller and smaller. According to field observations: old vegetable fields used for seedling raising and continuous cropping; early seedling raising before "Autumn Equinox" leads to more bolting the following spring; onion seedlings planted after being sun-dried until half dry; serious occurrence of thrips and aphids during the seedling stage; soil drought after planting and revival; years with high temperature in July and relatively little rainfall have more severe disease.
In view of the occurrence characteristics of Welsh onion dwarf disease, adopting comprehensive cultivation measures can greatly reduce the occurrence of this disease. (1) When raising seedlings, choose disease-resistant varieties such as Zhangqiu Dawutong, Wuyeqi and their first-generation hybrids, Luoyang Dongqing, Tangshan Dubai, etc.; (2) Change early seedling raising before "Autumn Equinox" to late seedling raising after "Autumn Equinox", and vigorously promote spring seedlings raised under plastic film mulching at "Spring Equinox"; (3) During the seedling stage, use a 1000-fold mixture of 40% dimethoate and 80% dichlorvos, adding a small amount of washing powder or waste soybean milk to increase adhesion (the following pesticide uses are the same), to control thrips and aphids; (4) Before planting onions, apply heavy base fertilizer, sort seedlings by grade, dip roots in 1000-fold dimethoate solution, and plant strong seedlings; (4) After planting and revival, spread wheat bran 250 kg/667 sq m or potato vines, fresh tender weeds 300 kg/667 sq m in the onion furrows to retain moisture and lower temperature, loosen soil and fertilize the field; (6) From August to October during the growing period, apply a special compound fertilizer for Welsh onions once at 50 kg/667 sq m, and apply urea 2 times at 20 kg/667 sq m each time. Coordinate topdressing with intertillage, hilling, and watering to promote strong seedling growth of Welsh onions; (7) Spray 2 times before planting onions, once every 7-10 days, and spray 3 times after planting with naphthalene acetic acid amine liquid, 1 vial diluted with 20 kg water, to prevent disease and strengthen plants; (8) If a small number of diseased plants still appear in the onion field, use 0.5% Kangbingsu No. 1 at 300-400 fold, or 25% Kangbingdu No. 1 wettable powder at 300 fold, or 1.5% Zhibingling at 400 fold for thorough control, ensuring strong growth and a bumper harvest of Welsh onions.