When crops are damaged by adverse circumstances, the first manifestation is the leaves, which often appear yellowing, disease spots, leaf curling, etc. Leaf curling can be divided into two types: upward leaf curling and downward leaf curling. phenomenon.

Leaf curling caused by inappropriate environmental conditions and improper cultivation management is physiological leaf curling. Physiological leaf curling will occur on the leaves of the entire plant. In some plants, only the lower or middle and lower leaves are curled. Some entire plants have curled leaves. Symptoms of mosaic leaves without clear veins. When leaf curling is severe, the leaves become thick and brittle. The leaf curling caused by viral diseases is caused by infectious diseases. It usually occurs on the new leaves at the top and is accompanied by bright-veined mosaic symptoms. The old leaves in the lower parts are less susceptible to damage, and the plants appear to be dwarfed to varying degrees. There are two types of leaf curling: upward curling and downward curling. The cause should be found out and the right medicine should be prescribed. The reason for leaf curling is high temperature, drought and lack of water

If you encounter high temperature (temperature continuously exceeds 35℃) or drought weather during the growth process and cannot replenish water in time, the leaves will roll upward.

When entering the fruiting period, if water cannot be replenished in time, the plant's leaf transpiration will be enhanced due to the large leaf area, high temperature and strong light during the growth process. The rate of leaf transpiration of water is greater than that of the root system. The speed of absorption and transport can easily cause the plant to be in a state of water shortage, so that the stomata of the leaves are forced to close, the surface of the leaves is dehydrated, and the lower leaves of the plant are easy to curl upward.

Preventive and control measures: For production in protected areas, sunshade nets should be added promptly, ventilation openings in greenhouses should be increased, and care should be taken not to remove insect-proof nets. If leaf curling occurs, you can also spray a new high-fat film to moisturize the leaves in time to reduce water evaporation in the leaves and delay their aging. Pay attention to frequent watering.

Ventilation problem. When the temperature difference between the inside and outside of the shed is large, if the wind is suddenly released, the exchange of cold and warm air inside and outside the shed will be relatively strong, which can easily cause the vegetable leaves near the vents to curl. This kind of upward rolling of leaves caused by ventilation conditions usually starts from the leaf tip. The leaves become chicken claw-shaped, and in severe cases, the stem tips have white edges.

Prevention and control measures: In winter, the temperature is 25-28℃ during the day and 12-15℃ at night; in summer, the temperature is 25-30℃ during the day and 15-18℃ at night. The ventilation should also be determined according to weather changes. When the outside temperature is low, the ventilation can be postponed or not ventilated appropriately, and the greenhouse should be mainly insulated to avoid freezing damage caused by sudden drops in greenhouse temperature.

The problem of phytotoxicity is that as the temperature rises, especially in summer, the temperature is relatively high. If you are not careful when spraying, phytotoxicity will occur. Once the concentration of the drug is too high, phytotoxicity will occur, and the surface of the leaves will Discoloration or spots may appear, and the leaves may curl upward.

Prevention and control measures: Rational use of pesticides. When the temperature is high in summer, the concentration should be lower. After pesticide damage occurs, spray water or spray brassinolide in time to alleviate the problem.

Excessive fertilization, if the crop uses too much fertilizer, will cause the concentration of the soil solution in the root system to increase, hindering the absorption of water around the root system, and causing the leaves to become water-deficient, causing leaflets to turn over and Roll up.