Pesticides have a certain shelf life. Once the crops use pesticides that exceed the shelf life, they will cause resistance to pests and diseases, delay the best period of prevention and control, and even cause phytotoxicity of crops. Several pesticide failure identification methods are introduced, which are available for reference by farmers.
Intuitive method
For powder pesticides, first look at the appearance of the pesticide product. If it is obviously agglomerated by moisture, the taste of the medicine is not strong or there are other abnormalities, and it can be formed into a group by hand. This kind of pesticide basically fails. For emulsifiable pesticides, the vial is first allowed to stand. If the turbidity of the liquid is unclear or stratified (ie, the oil moisture layer), precipitates are generated or floc is suspended, the pesticide is ineffective.
Heating method
It is suitable for powder pesticides. Take 5-10 grams of pesticide samples and heat them on a piece of metal. If a large amount of smoke is produced and there is a strong pungent odor, the pesticide samples have good performance. Otherwise, it means that there is no active ingredient of pesticide.
Floating method
Applicable to wettable powder pesticides, first take 200g of water, then weigh 1g of pesticide sample, gently spread evenly on the water surface, carefully observe, within 1 minute, wet and soluble in water is not invalid Pesticide, otherwise it will be invalid.
Oscillating method
Suitable for emulsifiable pesticides. For pesticides with oily water layer, first shake the vial vigorously and let it stand for 1 hour. If stratification still occurs, the pesticide has failed.
Dilution method
Suitable for emulsifiable pesticides. Take 50 grams of pesticide sample, put it in a glass bottle, add 150 grams of water, shake it vigorously and let it stand for 30 minutes. If the liquid is uniform milky white, and there is no oil on the oil, there is no precipitation under it, indicating that the pesticide is good, otherwise it will be invalid. . The more the upper layer of oil slick, the worse the quality of the pesticide.
Suspension method
Suitable for wettable powder pesticides. Take 30-50 grams of pesticide samples, put them in a glass container, add a small amount of water to make a paste, then add 150-200 grams of water and mix well. Allow to stand for 10 minutes to observe. The pesticides that have not failed are well soluble and suspended in the liquid. The powder is fine, the sedimentation rate is slow and the amount of sedimentation is small, and the pesticide is reversed.
Hot melt method
Suitable for emulsifiable pesticides. Put the pesticide with the precipitate into the warm water (the water temperature should not be too high, preferably 40 ~ 50 ° C), and observe it after 1 hour. If the precipitate dissolves, it means that the emulsifiable concentrate has not expired. After the precipitate is dissolved, it can be reused. If the precipitate is difficult to dissolve or dissolve, it indicates failure.
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