Onion (green onion, onion) purple spot disease, also known as black spot disease, mainly damage leaves and pedicels. The onset spreads up from the tip of the leaf tip or the middle of the pedicel, with small purple-brown spots or spindle-shaped depressions. It has dark brown powdery mildew during the wet period. Several lesions merge with each other or surround the leaves and pedicels. The department is soft and easy to break, and when it is severe, a large number of leaves die. The high incidence of pedicels in the plant strains causes the seeds to shrink and fail to mature sufficiently. Bulb damage causes semi-humid rot and shrinks black.
Onion purple spot is a fungal disease caused by Onytis sp., mostly mycelium or conidia with the disease in the winter in the soil, the second year after conidial germination from the pores or wound invasion parasites, The optimal incidence is 24°C-27°C, and less than 12°C is less likely to develop. The disease is not strict with the environmental conditions, generally warm and humid, even rainy days, lack of fertilizer, drought, plant growth weakness, when the onion thrips caused wounds, the incidence is serious.
Control methods:
1. Dispose of sick bodies in time and implement 1-2 year rotation with non-onion vegetables.
2. Strengthen field management, select high-desert, well-drained plots for cultivation; rational fertilization; do a good job of drainage work after the rain, so that plants grow robustly, and enhance disease resistance.
3. Control the onion thrips in time to avoid causing wounds.
4. Take disease-free fields or use disease-free seedlings. To disinfect the seed, use 30% formaldehyde for 3 hours with 40% formaldehyde and wash it in time after leaching. Bulb disinfection can be soaked in warm water at about 45°C for 1.5 hours.
5. Apply 75% chlorothalonil wettable powder 500-600 times liquid or 70% mancozeb WP 500 times liquid, 64% antivirus WP 500 times, 40% EB aluminum wettable Powder, 50% acetaminophen wettable powder 1500 times, onion bacteria net 300-500 times, 58% thiram Mn-Zn wettable powder 500 times spray or root, 5-7 days, even spray 3-4 times.
6. In the initial stage of disease, 50 grams of 15% Manor Water Reagent is applied per 1,000 square meters, mixed with 25-30 grams of Tian Xiucai No.7 and 100 milliliters of small leaf enemy antiviral nutrient solution, 20 kilograms of water, after 4 pm on sunny days. Field spray, spray once every 5-7 days, even spray 3 times, better control effect. Due to the smooth surface of the onion leaves, in order to increase the adhesion, 1.5 kilograms of soy milk or 0.1 kilograms of synthetic laundry detergent or an appropriate amount of vegetable oil can be added to 50 kilograms of medicinal liquid.
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