1. Residual phytotoxicity This phytotoxicity is characterized by no phytotoxicity to the seasonal crops after application, and the medicinal agents remaining in the soil produce phytotoxicity to crops that are more sensitive to diarrhea. For example, after the use of simazine herbicide in corn fields, it often causes phytotoxicity to crops such as beet, beans and fruit trees. The phytotoxicity is mostly manifested in the germination or seedling stage of the seed. The light roots, buds and other parts of the light brown rot, affecting normal growth, and the rotted buds are severely rotted, reducing the emergence rate or not emerging at all. Because this phytotoxicity is easily confused with fertilizers, it is necessary to understand the cultivation management and pesticide use of the former stalks and soil testing before the diagnosis to prevent misdiagnosis.
2. Chronic phytotoxicity, this symptom can not be immediately expressed after application, and has a certain incubation period, such as growth retardation, fruit and flavor deterioration. Because of this phytotoxicity, it is easily confused with other physiological diseases. Therefore, it can be diagnosed by understanding the occurrence of pests and diseases, the type, quantity, area of ​​the pesticides and the comparison with the plants that are not normally applied.
3. Acute phytotoxicity This phytotoxicity has the characteristics of rapid occurrence and obvious symptoms, and symptoms usually appear within a few hours to several days after application. Generally, the crop leaves are spotted, perforated, burnt, curled, deformed, withered, yellowed, chlorotic or whitened. The damage of the affected part is characterized by short and coarse roots, weak root hair, yellowing or thickening of the root bark, and rot, etc. Pesticides or pesticides are used for improper seed treatment; plants are damaged, which are characterized by falling flowers, buds, fruit deformities, small, spots, brown fruit rust, fruit drop and so on.
2. Chronic phytotoxicity, this symptom can not be immediately expressed after application, and has a certain incubation period, such as growth retardation, fruit and flavor deterioration. Because of this phytotoxicity, it is easily confused with other physiological diseases. Therefore, it can be diagnosed by understanding the occurrence of pests and diseases, the type, quantity, area of ​​the pesticides and the comparison with the plants that are not normally applied.
3. Acute phytotoxicity This phytotoxicity has the characteristics of rapid occurrence and obvious symptoms, and symptoms usually appear within a few hours to several days after application. Generally, the crop leaves are spotted, perforated, burnt, curled, deformed, withered, yellowed, chlorotic or whitened. The damage of the affected part is characterized by short and coarse roots, weak root hair, yellowing or thickening of the root bark, and rot, etc. Pesticides or pesticides are used for improper seed treatment; plants are damaged, which are characterized by falling flowers, buds, fruit deformities, small, spots, brown fruit rust, fruit drop and so on.
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