Spinach leaves have yellow spots and black hairs behind them. How to treat them?

Spinach can be weeded by "grass shower" before it is planted underground. The growth period of spinach depends on what grass grows and the appropriate herbicide is selected. Symptoms and characteristics of common diseases and insect pests in spinach control virus disease (1) can be infected from seedling stage to adult stage, and diseased plants in the field often show different symptoms. Its typical symptom is that the young leaves are mottled, embedded in the shade of green, and the leaves are flat without shrinkage. Some diseased plants have white leaves, the base of which fades outward, but the tip is still normal green. Some show that the veins are yellow and slightly transparent, the veins are still normal green and the leaves are shriveled. The leaves of some diseased plants are narrow and deformed, and in severe cases, they are fernlike. There are also diseased plants whose heart leaves shrink into a ball and the plants are dwarfed. It is spread by aphids and juices. The land with drought, poor ventilation and overgrown weeds is seriously ill. (2) Control methods ① Clear weeds in the field in time. ② Strengthen field management, timely sow and water, reduce ground temperature and change field microclimate. (3) Apply sufficient organic fertilizer to make nitrogen, phosphorus and potassium cooperate to improve the disease resistance of spinach. ④ timely control aphids. Spraying 20% pyrethroid 2000 ~ 3000 times solution, or 40% dimethoate 1000 times solution and 50% pirimicarb 2000 ~ 300 times solution for control. ⑤ Spray 1.5% phytosanitary emulsion 1000 times, or 300 times of antitoxic agent 1.500 times of 20% virus A wettable powder, etc. At the initial stage of the disease, it should be sprayed once every 10 days, and it usually needs to be sprayed continuously for 2 ~ 3 times. However, due to the short growth time of spinach, it is rarely used after the onset. The key lies in the treatment of aphids and the prevention of seedling stage. Downy mildew is the most common disease in spinach growing areas in southern China. This disease is caused by a fungus called spinach mold. The symptoms of injury in the field are as follows: it mainly harms the front of leaves, and the lesions are yellowish, irregular and unequal in size, with a diameter of 3- 17 mm and an inconspicuous edge. The lesions expanded and connected with each other, and later turned brown and died. Gray-purple mold layer is produced on the diseased spot on the back of leaves. The disease gradually developed from the outer leaves to the inner leaves and extended upward from the lower part of the plant. The diseased leaves turn yellow in drought, rot in high humidity, and turn yellow and die in severe cases. When the temperature is 10℃ and the relative humidity is 85%, or when the planting density is high and the water is accumulated, the disease is serious. Because spinach downy mildew overwinters in overwintering vegetable plants, seeds or diseased leaves, it spreads through wind, rain, farm tools, insects and agricultural operations in the following spring under suitable environmental conditions, and the pathogen invades from the host epidermis or stomata. The following measures should be taken to control downy mildew of spinach: 1, and the cultivation management should be strengthened. Reasonable close planting, scientific irrigation, reducing field humidity; 2. Choose disease-resistant varieties. Sawo hybrids 6 12, 62 1, Banti, Banas, Duet and other famous varieties can be selected, and sharp-leaved varieties can also be selected; 3. Collect seeds in disease-free land or plants. If the seeds carry bacteria, the seeds can be dressed with 50% thiram wettable powder before sowing, and the dosage is 0.4% of the weight of the seeds; 4. In early spring, if a diseased plant is found in the spinach field, it should be pulled out in time, taken out of the field and burned; 5. At the initial stage of the disease, spray 200-250 times of 40% krill wettable powder, 200-250 times of 40% krill wettable powder, 500 times of 58% metalaxyl manganese zinc wettable powder, 500 times of 64% antiviral alum wettable powder, or 800 times of 72.2% water solution. Spinach Fusarium wilt generally occurs more seriously in adult stage. It shows that the old leaves darken and lose luster, the mesophyll gradually turns yellow and expands upward, and the roots turn brown and die when they develop downward. Early-growing plants are obviously dwarfed. When the weather is dry and the temperature is high, the diseased plants will wither quickly. Under wet and low temperature conditions, diseased plants can continue to survive for a period of time, and sometimes new lateral roots can grow. But in hot weather, you will die soon. The pathogen of spinach Fusarium wilt mainly spends summer or winter in soil or seeds with plant disease residues. Seeds can carry bacteria, so can immature fertilizers. Bacteria can spread with rainwater and irrigation water, directly invade from root wounds or root tips, and reach vascular bundles after invasion. In the vascular bundle, bacteria produce toxic substances, block the catheter, and cause the leaves to wither and die. High temperature and high humidity are conducive to the onset; The soil temperature is about 30 degrees Celsius, the soil is moist, the fertilizer is not fully decomposed, there are many underground pests, and nematodes are prone to disease. Control methods: 1, rotate with onion and Gramineae crops for 3-5 years to avoid continuous cropping; 2. Apply compost or fully decomposed organic fertilizer made by Japanese ferment bacteria and adopt formula fertilization technology to improve the disease resistance of the host; 3. Adopt high ridge cultivation or ridging cultivation, drain water in time after rain, and flood irrigation is strictly prohibited; 4. Pull out the central diseased plant in time, and spray 1500 times of 50% benomyl wettable powder, 500 times of 40% polysulfide suspending agent, or 300-400 times of 10% water solution for 2-3 times in a row once every half month. The symptoms of spinach white spot disease are mainly manifested in leaves. The lower leaf comes on first, and the lesion is round to nearly round, with obvious edge, 0.5-3.5 mm in size, yellow-white in the middle, brown to purple-brown in the outer edge, and gradually develops into white spots after expansion. When the humidity is high, gray hairs can be seen on some lesions, and when the dry-wet conversion is fierce, the middle of the lesions is easy to break. This symptom is caused by Cercospora beet infection. This fungus can not only harm spinach, but also harm Chenopodium plants such as sugar beet, causing similar symptoms. The pathogen of spinach white spot overwinters in the soil with mycelium and disease, and spreads by wind and rain in the next spring. Weak growth potential, easy to get sick under warm and humid conditions, low-lying, nest wind, poor management, serious illness. Control method: 1. Choose a ventilated plot with flat terrain and sufficient organic fertilizer to plant spinach, water it properly and manage it carefully to improve the disease resistance of plants; 2. Remove the sick and disabled bodies in time after harvest, and bury or burn them centrally to reduce the source of the disease; 3. At the initial stage of the disease, spray 400-500 times of 30% Ludebao suspension, or 1:0.5: 160 times of Bordeaux solution, 75% chlorothalonil wettable powder and 50% carbendazim wettable powder1000-1. Anthracnose mainly harms leaves and stems. Leaf infection, the primary yellowish spots gradually expand into taupe, round or oval spots, with wheel lines and small black spots in the center. Spread by wind and rain, directly invade from the wound or epidermis. Heavy rainfall, low terrain, over-dense planting, and serious plant growth and development. Prevention and control methods ① Choose seeds without diseases, or soak them in warm water at 25℃ for 20 minutes before sowing, then move them into cold water for cooling, and then dry them before sowing. ② Rotation with other vegetables for more than 3 years. (3) reasonable close planting, timely drainage after the rain; Timely topdressing, pay attention to the coordination of nitrogen, phosphorus and potassium. (4) Clean the countryside, remove the sick and disabled in time, take them out of the field and burn them or bury them deeply. ⑤ Spraying 700 times solution of 50% carbendazim wettable powder, or 600 times solution of 40% polysulfide suspending agent and 500 times solution of 50% thiophanate-methyl wettable powder at the initial stage of onset. Give priority to prevention, and stop spraying 10 ~ 15 days before harvesting. Spinach aphids mainly harm overwintering spinach before winter and after spring. In the middle and late period of spinach growth in spring, aphid damage is aggravated due to the rising temperature. Its pollution-free control technology is as follows: 1 Clear the field in time and do a good job in the prevention and control of aphids in surrounding vegetable fields. 2. Give dense seedlings and weak seedlings regularly to facilitate ventilation and strong seedlings. Combined with heat preservation and antifreeze, covered with silver-gray sunshade net to avoid aphids. 4. Chemical control: spraying 20% pyrethroid 2000 ~ 3000 times solution, or 40% dimethoate 1000 times solution, 50% pirimicarb 2000 ~ 3000 times solution, etc. Pay attention to early prevention and control, and stop spraying 10 ~ 15 days before harvesting. Hazard characteristics of spinach leaf miner: Spinach leaf miner is also a kind of spring fly. Harm spinach and radish. Larvae feed on mesophyll in submerged leaves, leaving only the upper and lower epidermis, which is a thick tunnel. Generally, there are 1 ~ 2 maggots with insect feces in the leaves, which makes spinach lose its commercial value and edible value. When spinach leaf miner can't find a suitable host, it can grow on manure or humus. The first generation occurred in spring. Because some pupae of each generation of spinach leaf miner entered diapause and emerged at the same time in spring, the insect population reached its peak. High temperature and drought in summer are not conducive to the occurrence of spinach leaf miner, which is serious in the north and rare in Changsha. Prevention and control methods ① Apply fully decomposed manure and avoid using unfermented manure. ② Due to the short growth period of spinach, we must consider the problem of pesticide residues and choose chemicals with short residual effect and easy photolysis and hydrolysis. In addition, because larvae do great harm to submerged leaves, we must grasp the key moment from the peak spawning period to the early hatching period. Commonly used pesticides are: 50% phoxim EC 1000 times, or 20% chlorfenapyr 2000 ~ 3000 times, 80% trichlorfon soluble powder and 90% trichlorfon crystal 1000 times. Pay attention to stop using the medicine 10 ~ 15 days before harvesting, and use it in combination with aphid control and use it alternately.