Alternating spraying buprofezin, copper thiamethoxam, streptomycin and zhongshengmycin, or mi
Alternating spraying buprofezin, copper thiamethoxam, streptomycin and zhongshengmycin, or mixing the two components with potassium dihydrogen phosphate with different mechanisms can prevent the yellowing of vegetable leaves. Continuous prevention and treatment for 2-3 times, once every 5-6 days. . Apply pesticide strictly according to the regulations, avoid using it at high temperature at noon, spray the liquid evenly, and don't spray it again or miss it. If there is any drug damage, rinse it with clear water in time.
First, what medicine is used for yellowing of vegetable leaves?
1. The yellowing of vegetable leaves may be caused by black rot. Bacterial drugs such as copper thiasone, copper thiamethoxam, agricultural streptomycin, zhongshengmycin, thiamethoxam, copper quinoline, etc. Alternating spray control or mixed spray control of two components with different mechanisms and potassium dihydrogen phosphate can be selected. Spraying once every 5-6 days, and continuous control for 2-3 times.
2. After the liquid medicine is prepared, the vegetable farmers should spray it in time. If it is left for a long time, the concentration of the upper liquid medicine is low and the concentration of the lower liquid medicine is high, which will lead to uneven spraying and phytotoxicity. In the process of spraying, it is necessary to pay attention to the consistent walking speed and even spraying of the liquid medicine, and it is not allowed to re-spray or miss spraying. It is advisable that the liquid medicine moistens the plant surface without producing droplets. Use drugs in strict accordance with regulations, avoid using drugs at high temperature at noon, and rinse with water as soon as possible to prevent drug damage.
Second, what causes the vegetable leaves to turn yellow?
1, watering too often
Too much soil moisture will hinder the roots from absorbing water and fertilizer, and if there is long-term hypoxia, the roots will rot. In the early stage of soil hypoxia, the changes of old leaves are not obvious, the young leaves are dark yellow and dull, the branches are small yellow-green, and the top leaves of new shoots are not shrinking and pale yellow. In the later stage, the old leaves gradually turned dark yellow and eventually withered and died.
2. Soil drought
The growth of new leaves is relatively normal, but the tip or edge of old leaves is withered, wilted, yellow and falls off from bottom to top.
3. Fertilization is too frequent
The nutrient concentration of soil solution is too high, which leads to the obstruction of vegetable infiltration and transportation, easy wrinkling of leaves, thick and dull new leaves and yellowing of old leaves.
4. The soil is too acidic and alkaline.
In alkaline soil, phosphorus, iron, magnesium, zinc and calcium are easy to form insoluble compounds, which will reduce the absorption of these elements by vegetables and lead to yellowing of leaves. If the soil is too acidic, too much aluminum, iron and manganese will be dissolved, and plants will be poisoned by too much absorption, which will easily lead to the loss of magnesium and other elements, and the veins of old leaves will easily lose green and yellow.
5, aphids, liriomyza sativae, whitefly, red spider, scale insects and other pests harm the leaves, causing the leaves to shrink and yellow, and even the whole leaves wither and fall off.
Third, how to prevent vegetable leaves from turning yellow
1. For the yellowing of vegetable leaves caused by excessive watering, the irrigation amount should be controlled in time, and the soil should be loosened for drainage to increase the ventilation in the greenhouse.
2. For the yellowing of vegetable leaves caused by too little watering, irrigation should be carried out in time according to the degree of dryness and wetness of the soil in the field and the state of vegetable leaves, and the principle of seeing dry and wet, not watering and pouring thoroughly should be mastered.
3. For the yellowing of vegetable leaves caused by excessive fertilization, fertilization and intertillage should be stopped immediately, and plants and topsoil should be washed with water.
4. For the yellowing of vegetable leaves caused by excessive soil acidity or alkalinity, acid should be adjusted and ferrous sulfate should be sprayed on the leaves. Before soil preparation, apply quicklime and spray calcium magnesium phosphate fertilizer on the leaves.
5. For the yellowing of vegetable leaves caused by pests, once pests and diseases are found in the field, they should be prevented in time.