There are many reasons for the phytotoxicity of seedlings: one is misuse of the pesticide that is not symptomatic or the herbicide is misused; the second is that the concentration of the pesticide is too large or repeated application; the third is the application under high temperature conditions; It is the application of inferior pesticides; the fifth is that the pesticide application method is not correct or the pesticides that cannot be mixed are simply mixed.

Control measures: First, timely water spray. If the leaves and plants cause phytotoxicity caused by spraying the liquid, if it is found in time, the leaves can be sprayed with a large amount of fresh water quickly after the early liquid has not fully penetrated, and the water is sprayed 3-4 times repeatedly to wash the liquid on the surface of the plant as much as possible. Drop and cooperate with cultivating loose soil to promote root development and quickly restore normal plant growth. The second is neutralization treatment, spraying plant growth regulators. According to the nature of the pesticide causing the phytotoxicity, the drug is neutralized by the opposite nature, such as copper sulfate spray, which can be neutralized with 0.5% quicklime. The third is to apply quick-acting fertilizer. According to the law of vegetable growth, after the vegetables are phytotoxic, the growth is often inhibited. At this time, water should be watered in time, and the water-soluble fertilizer should be applied.

The wilting seedlings were mostly caused by the continuous rainy weather and the weather was suddenly cleared.

Control measures: First, in the event of a sudden cloudy day, the seedlings should gradually see the light, do not immediately uncover all the covers, should be removed in batches, gradually increase the light; ventilation in the high place of the shed, using the air outlet The size and length of the air release time to adjust the temperature of the seedbed, avoid the bottom wind. Second, shortly after the opening of the sunshade net, if the seedlings are wilting, they should be covered immediately. After the seedlings return to normal, they should be uncovered and watered. The third is water spray and temperature control. Spray water to increase air humidity, this is open source. When the air humidity is high, the transpiration of the leaves is significantly reduced, which is the main reason for the large leaves and large pores of the vegetables in the greenhouse.

The root damage caused by the high humidity and high temperature of the bed roots is characterized by yellowing and wilting of the leaves, and the seedlings stop growing.

Control measures: First, reduce humidity in time. Select a soil with strong gas permeability as a seedbed. When nursery in a greenhouse or a greenhouse, the water should not be watered or watered as much as possible when the seedbed is not obviously dry. The amount of water should not be too large when the drought is obvious. The humidity in the bed is too large, it can cover the hay wood ash, and it can also be properly ventilated and drained. The second is to apply enough farmyard manure. Vegetable seedlings, to increase the application of farmyard manure, can not only fertilize the soil, cultivate strong seedlings, improve the disease resistance of vegetable seedlings, but also increase the ground temperature and reduce the occurrence of diseases. The specific method is: before the vegetable seedlings, mix the fully decomposed farmyard manure with the bed soil. The third is timely ventilation. After the cotyledons are unfolded, the cover is ventilated, and a layer of fine dry soil is evenly applied to the seedbed, and then the cover is tightly covered, thereby reducing the humidity of the bed soil. Fourth, in the event of rooting, it is necessary to ventilate and dehumidify in time, or to apply fine dry soil and grass ash to absorb moisture. The fifth is cultivating loose soil. In general, most vegetable roots grow well when the soil oxygen concentration is above 8%. Due to poor gas permeability and root and microbial activity, the oxygen concentration is much lower than that of the atmosphere. Especially in the case of soil compaction and water accumulation, the anaerobic respiration of roots leads to an increase in toxic substances, which is not conducive to root growth.