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1. Strictly grasp the sensitivity of crops to herbicides. The sensitivity of crops to herbicides varies. If pesticides are not selected according to the sensitivity of crops to herbicides, even if they are used as safe herbicides, it is sometimes easy. Produce phytotoxicity. Herbicides that generally control broadleaf weeds are sensitive to dicotyledonous crops, and herbicides that control grass weeds are sensitive to gramineous crops. For example, 2,4-D, Dimethyltetrachloride and the like have good effects on broad-leaved weeds, but are sensitive to broad-leaved crops such as cotton, rapeseed, melons, beans, peanuts, potatoes, tobacco, etc., which are prone to phytotoxicity. . Acetochlor is suitable for broad-leaved crops such as corn, peanuts, cotton, and soybeans, but it is susceptible to phytotoxicity to wheat. It can be used to control grass weeds in broad-leaved crop fields, but it is harmful to gramineous crops such as wheat, rice, millet and corn.
2. Strict control of crop sensitive period and application period Crops are sensitive to insecticides and fungicides at different growth and development stages, and their sensitivity to herbicides is different. Under normal circumstances, crops are particularly sensitive to herbicides during germination, pre-leaf 3 and flower filling stages, and these periods are prone to phytotoxicity. Pre-emergence herbicides can only be absorbed by the radicle, spore or hypocotyl of weeds, killing weeds and using them after weed emergence. Generally, there is no herbicidal effect or low herbicidal effect. Post-emergence herbicides are also safe and effective for use in weeds or crops at a certain stage of growth. For example, the grass grass can be used in the 3 to 5 leaf stage of weeds, and the control effect on grass weeds is usually 90 to 100%, but the effect is lower after the 5 leaf stage.
3, the strict selection of herbicide types Herbicides have the following types, should be "made by grass". (1) Selective herbicides: These herbicides are used within a certain dosage range to selectively kill certain harmful plants while crops are safe. Proper use in crop fields can achieve the goal of killing only weeds without harming the crops. (2) Killer herbicides: These herbicides have a killing effect on all plants, such as gram-free, sodium pentachlorophenol, glyphosate and the like. Such herbicides are limited to grass fields in leisure fields and idle places. (3) Contact-type herbicides: These herbicides only damage the parts of the plant that come into contact with the drug, and have no effect on the parts that are not exposed to the drug, such as gram-free, enemy, and herbicide ether. (4) Systemic-type herbicidal type: The active constituents of such herbicides can be absorbed by the roots, stems and leaves of plants and rapidly transmitted to the whole plant, thereby killing harmful plants such as glyphosate, covering grass and stabilizing Ether, etc.
4. Strictly control the amount and concentration of herbicides The selectivity of herbicides is selective within a certain dosage range. Therefore, even selective herbicides may cause phytotoxicity to crops beyond the specified dosage range. For example, the dosage of 60% butachlor EC in rice field exceeds 0.15 liter/mu, the amount of 48% trifluralin in cotton seedbed exceeds 0.1 liter/mu, and the dosage of 10% oxacilin in rice field exceeds 0.3 liter/mu. 50% of the amount of Weiluosheng in the 10 days after planting will exceed 0.3 liters/mu, which will cause crop phytotoxicity. 2,4-D butyl ester has certain selectivity to wheat, but when the dosage is too large, it will also kill wheat or severely deform wheat plants, affecting yield. In addition, the appropriate use of herbicides is also affected by factors such as crop type, soil texture, climatic conditions and application methods. If the herbicide is used at a high concentration, it must not be re-sprayed, otherwise it may cause the local application concentration to be too large, and local phytotoxicity may occur.
5, the use of strict herbicides Herbicides use methods include stem and leaf treatment, soil treatment and herbicide weeding. At present, the most commonly used methods are stem and leaf treatment during the growth period and soil treatment before sowing. Stem and leaf treatment during the growth period is a method of spraying herbicides on weed stems and leaves at a certain growth stage after crop emergence. In this way, the herbicide not only contacts the weeds, but also may contact the crop, so the herbicide is required to have a higher selectivity or directional spray for the purpose of safe application. The post-emergence soil treatment after sowing is a method of spraying the herbicide on the soil surface before the crop is planted. Most soil treatment agents are used in this way. Stem and leaf treatment herbicides usually fall into the soil and are quickly passivated or decomposed by microorganisms to lose herbicidal activity, while soil treatment herbicides are generally ineffective against weeds after emergence. Therefore, when using the method according to the herbicide characteristics, the effect can be fully achieved and the negative effects can be avoided.
6, strictly follow the principle of mixed herbicides in production, sometimes to kill a variety of weeds, several herbicides need to be mixed, but not all herbicides can be mixed, herbicides must be used in strict accordance with the following Principle: 1 mixed herbicides must be different from the killing spectrum. 2 mixed herbicides, the use period and method must be the same. 3 After the herbicide is mixed, precipitation and delamination cannot occur. 4 After the herbicide is mixed, the amount is 1/3 to 1/2 of a single amount. In addition, for the herbicides that are not mixed with each other, the method of staging can also achieve the purpose of killing weeds. Its application method: alternately use herbicides on the same soil. For example, the use of trifluralin to kill the grass, and then use the cull to kill the broadleaf weeds; soil treatment and post-emergence stem and leaf treatment.