Pesticide Damage to Crops and Preventive Measures
The phytotoxicity refers to various morbidity reactions that plants produce when improper use of pesticides. There are points for acute injury and chronic injury.
Acute injury refers to the symptoms within a short period of time (generally within 10 days), usually the leaves soon appear spots, chlorosis, yellowing, etc.; the fruit is brown, the surface of the drug spots or falling fruit; root dysplasia Or form black roots, chicken feet and so on.
Chronic phytotoxicity refers to symptoms only after 10 days of treatment, usually yellowing, dwarfing, small fruit, and inferior fruits. Because of the variety of plants, their ecological habits are different. In addition, some species live in greenhouses and greenhouses for a long period of time, and their tissues are young, often causing phytotoxicity due to improper use of drugs. The causes and prevention measures are as follows.
1. Causes of injury
(1) Improper selection of drug type
For example, Bordeaux has a high concentration of copper ions and is used in woody plants. Herbs are prone to phytotoxicity due to their young tissue. Lithosulfur is effective in controlling powdery mildew, but due to its corrosiveness and strong alkalinity, it is easy to produce phytotoxicity when used in herbaceous plants.
(2) Some plants are allergic to certain pesticide species
Even in normal use, it is easy to produce phytotoxicity. Such as peaches and flowers, cherry blossoms and other sensitive to dichlorvos, peaches, plums are sensitive to dimethoate and Bordeaux mixture.
(3) Use during the sensitive period of plants The flowering period of various plants is one of the most sensitive periods for pesticides. At this time, the plants are susceptible to phytotoxicity.
(4) It is easy to produce phytotoxicity when high temperature, heavy fog and relative humidity are high
When the temperature is high, the plants absorb the medicine and transpiration quickly, so that the medicine quickly concentrates on the tip of the leaf and the leaf edge and produce phytotoxicity. When the fog is heavy and the humidity is high, the drug droplets are distributed unevenly and are prone to phytotoxicity.
(5) High concentrations, large dosages To overcome the resistance of diseases and insect pests, etc., and optionally increase the concentration and dosage of pesticides, it is easy to produce phytotoxicity.
(6) Misuse of phytotoxicity
It refers to the phytotoxicity caused by misuse of certain crops because they cannot be used for a certain crop. Although this situation is not always happening in production, the consequences of the occurrence of phytotoxicity are very serious, especially the misuse of herbicides. For example, 2,4-D butyl ester was misused in watermelon fields.
(7) The phenomenon of uncleaned containers or sprayers will occur from pesticide production to field use. This phytotoxicity accident is one of the most prone to phytotoxicity, and it occurs more than once a year.
(8) Product quality
In one case, the quality of the pesticide itself is poor, and there are many impurities, causing phytotoxicity when used. The same product, such as acetochlor, imported and domestically produced products of different manufacturers have different sensitivities to crops. Another situation is improper management of pesticides, long storage time, causing stratification, sedimentation, agglomeration and other phenomena. The deterioration of pesticides not only causes waste, but also easily causes phytotoxicity.
(9) Unreasonable mixing of pesticides
The rational use of pesticides has many advantages, but the principle of mixed use should be followed. If the pesticides are used improperly, it will also cause injury. Mixtures of Bordeaux mixture and lime sulfur are prone to phytotoxicity.
2. Crop phytotoxicity symptoms
spot
Spot phytotoxicity mainly occurs on the leaves, sometimes on stems or fruit epidermis. Common brown spots, macula, spots, net spots and so on. Such as Bordeaux mixture on the surface of the apple to produce a brown network of cork tissue; spraying lenguamycin watermelon seedlings, leaves will appear small yellow-shaped phytotoxicity.
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