1. Virus disease damage. Virus disease can easily lead to curling of tomato plants and leaf curling. In severe cases, only leaf veins and no mesophyll are involved. Viral diseases are transmitted through infected aphids, whiteflies, or sap, and high-temperature and dry conditions are favorable for this. Control measures: selection of disease-resistant varieties; implementation of crop rotation to reduce the initial infestation source; spraying 1000 times potassium permanganate at the early stage of the disease; using 10% net 1500-2000 times to kill the aphid and acaroid mites.
2. Physiological roll. Before and after the harvest of the tomato, the first ear was slightly rolled, or the whole leaf was curled into a tube and became brittle. This was mainly due to high temperature and drought, and the stomata of the tomato was closed and the leaf curled. Preventive measures: timely watering and fertilizer application after fruiting, covering the shade net, cover during sunny day and night, exposing at night, and not covering cloudy days.
3. Tea is damaged. Symptoms are narrowing of the leaves, stiffness, erection, shrinkage, or distortion, and finally, baldness. The control agent can be sprayed with 1.8% afordin 3000 times solution.
4. The lack of disease. The lack of phosphorus showed purple backs, brown spots on the leaves, the lower leaves rolled up, the leaves turned yellow, and the tip dark brown withered. Can be applied to soil by applying phosphate fertilizer, or foliar application of 0.3% potassium dihydrogen phosphate solution. Magnesium deficiency manifested in the first inflorescence fruit expansion period. The lower part of the plant's gray leaves lost chlorosis and yellowing appeared between veins. Then it expanded upwards to form yellow variegated leaves. When severe, the leaves were stiff or rolled up on the edges, and necrotic spots appeared between veins. Brown block band. Magnesium deficiency can be solved by applying 100% solution of full-element fertilizer or foliar spray magnesium sulfate.
5. Hormonal injury. In the use of plant hormones to prevent flowering and fruit drop, if 2,4-D is accidentally picked up on young leaves or growing points, there will be bending of the leaves or growing points, the new leaves will not be able to spread properly, and the green leaves will be distorted. Prevention and control measures: Select the appropriate concentration when using, generally use the concentration of 15 ~ 20 mg / kg, the concentration is lower when the temperature is high. When using, be careful not to spray the liquid onto the leaves or growing points. Do not spray it. After the occurrence of phytotoxicity, some growth-promoting nutrient liquids can be applied, such as natural brassinolide spray and love overdose.
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