Nicosulfuron is the most common herbicide in corn field, and the occurrence of nicosulfuron chlorination occurs. The pesticide network in China has prepared the conditions and prevention methods of nicosulfuron. First, the symptoms of phytotoxicity After 5 to 10 days of spraying the nicosulfuron in the 3~5 period leaves of corn, the heart of the corn is chlorotic and yellow, or irregular chlorotic spots appear in the leaves. Some of the leaves are curled into a tube shape, the leaf margins are shrunk, and the heart leaves are ox-tailed and cannot be properly withdrawn. Corn growth is inhibited, plants are dwarfed, and partial clumps and secondary stems may be produced. The light damage can restore normal growth and seriously affect the yield. Second, the cause of phytotoxicity 1. Excessive dosage is not used according to the prescribed dosage used by herbicides. It is misunderstood that increasing the dosage can improve the herbicidal effect, resulting in excessive dosage and high concentration. 2. Improper use of the drug The sensitivity of the crop to the herbicide varies with the growth period. The safe period of use of nicosulfuron in post-emergence is 3~5 leaf stage of corn, below 2 leaves stage or above 6 leaves, which is easy to produce phytotoxicity. 3. Improper application of pesticides Some farmers do not know enough about herbicides, do not strictly follow the instructions for use, apply non-directional spray after the 5th leaf stage of summer maize, or even use with pesticides , apply a large amount of liquid to corn heart leaves. Artificially caused phytotoxicity. At the same time, the application of organophosphorus pesticides to corn is sensitive to nicosulfuron, so the interval between the use of organophosphorus pesticides and no more than 7 days will also cause phytotoxicity. 4. The sprayer is not cleaned. The sprayer that has been used in soybean fields or herbicides has not been thoroughly cleaned in time, and then sprayed with nicosulfuron, which is easy to cause phytotoxicity to corn. 5. Poor performance of the sprayer or non-standard work in the field. If the flow rate of the nozzle of the multi-nozzle sprayer is inconsistent, such as dripping, etc., the partial spray volume is excessive. When the medicine is sprayed, the spray is uneven, and the spray webs are overlapped, resulting in excessive local spray volume and easy damage to the corn. 6. Weather Causes There is less rainfall in the early stage of corn growth, high temperature and drought, which is easy to affect the growth of corn. The growth of corn is slow, the resistance to herbicides is reduced, the function of decomposing phytotoxicity is reduced, and many latent phytotoxics are converted into dominant drugs. harm. After application, the temperature is low and rainy, the light is less, and the corn is also prone to phytotoxicity. 7. Individual maize varieties are themselves sensitive to nicosulfuron, such as sweet corn and popping varieties. Different types of corn have different tolerance to the agent, and the order of tolerance is hard grain > general type > sweet type > burst type. Third, preventive measures 1. Accurate calculation of the dosage According to the soil, climatic conditions, and grass conditions, determine the dosage of nicosulfuron. It is necessary to quantify the area, use the area, accurately dilute, spray evenly, do not re-spray, do not leak, can not Feel free to increase the concentration of the drug and the number of sprays. 2. Strictly apply the scientific application of pharmaceutical liquids to determine the application period of the pharmaceutical liquid, not only to consider the sensitive period of weeds, to strive for good control, but also to select the season crops with strong resistance and time for the safety of the crops. . At the 3~5 leaf stage of maize, the resistance to nicosulfuron was the strongest, and it was safest at this time. If it is used after the 6-leaf stage of corn due to weather and other reasons, try to spray it as much as possible, and avoid the corn leaf. Generally, before the corn 2 leaf stage and after the 10 leaf stage, the drug is sensitive and should not be used. At the same time, the drug solution should be diluted accurately, and then sprayed evenly after mixing. 3. Improve the level of application of chemical technology in addition to the operating procedures Guide farmers to eliminate the existing poor performance of the old manual sprayer, the introduction of good performance, high efficiency, low cost, new sprayer. At present, the WS-16P manual sprayer produced by Shandong Weishi Plant Protection Machinery Co., Ltd. and the Taishan -18AC knapsack mobile spray duster produced by Shandong Huasheng Agricultural Medicine Co., Ltd. Because nicosulfuron is an ultra-efficient herbicide, heavy spray and drip, it is easy to cause local drug concentration to be too large and cause phytotoxicity. In addition, before each medication, ensure that the sprayer is clean, so as not to cause corn phytotoxicity caused by other pesticide residues on the medicine. In addition, coating corn seed with naphthalic anhydride can reduce the phytotoxicity caused by the action of nicosulfuron and organophosphate insecticides. Fourth, remedies Under normal circumstances, the resistance of corn itself is strong. When nicosulfuron produces slight phytotoxicity, it does not need to be treated. Corn growth is only temporarily suppressed, and it can be recovered after a period of time without affecting the yield. If the phytotoxicity is heavy and needs to be treated, the following measures can be taken: 1. Detoxification in time When the chlorpyrifos has occurred or is about to occur, take measures to detox as soon as possible. For the initial phytotoxicity on corn plants, the pesticide residues on the plants can be washed off with water spray 3 to 5 times. 2. Strengthen field management (1) Pour enough water to promote the corn roots to absorb a large amount of water to reduce the concentration of herbicides in the plants and alleviate the phytotoxicity. (2) Appropriately increase the depth and frequency of depression, enhance the aeration of soil, promote the activities of beneficial microorganisms in the soil, accelerate the decomposition of soil nutrients, enhance the absorption capacity of corn roots for water and nutrients, and restore the normality of maize plants to normal as soon as possible. Growth and development. (3) Spraying Yunda-120 (natural brassinolide) diluted 1500 times or gibberellin plus 1% urea aqueous solution or diluted 500 times with detoxification and foliar, after morning dew or evening use The sprayer sprays the front and back of the blade to promote the normal growth of the plant to effectively reduce the phytotoxicity. (4) The corn field where the phytotoxicity occurs should be combined with watering to increase the application of manure, manure, ammonium bicarbonate, ammonium nitrate, urea and other quick-acting fertilizers to promote root development and regeneration, restore the physiological functions of the damaged corn, and reduce the smoke. Sulfasulfuron phytotoxicity damages corn. At the same time, it is also beneficial to restore the normal growth of corn by spraying 1%~2% urea or 0.2%~0.3% potassium dihydrogen phosphate solution or Huimanfeng 600~800 times. At the same time, it should also actively prevent other corn pests and diseases to improve the ability of corn to resist phytotoxicity. If the damage caused by the corn field is too heavy and the above measures can not alleviate the degree of damage, then only the destruction or replanting of other crops can be taken to avoid further losses. 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