Although many bactericides on the market are exposed to drug resistance problems, as of now, there is little news about the resistance of Bordeaux liquid, but the bottling problem of Bordeaux is the most troublesome problem, then to Bordeaux. What are the liquid-sensitive fruit trees? What is the way to reduce the problem of Bordeaux liquid phytotoxicity? First, the cause of the phytotoxicity of Bordeaux mixture 1. When preparing Bordeaux mixture, the copper sulfate is not completely dissolved. When the medicine is sprayed on the fruit together with the dregs, the fruit will appear reddish brown stains and reduce the commercial value of the fruit. 2. The use of Bordeaux mixture in the young fruit stage and fruit ripening of apples will cause rust spots on the fruit surface, rough skin and reduced smoothness, resulting in a decrease in the appearance quality of the fruit. 3, peach, apricot, plum tree growing season is sensitive to copper, the use of Bordeaux liquid is prone to copper ion poisoning, leading to defoliation, fruit drop. When the amount of lime in the Bordeaux mixture is lower than the multiple amount, the apple, especially the golden crown variety, the hawthorn, the persimmon tree, etc. are susceptible to phytotoxicity. When the amount of lime is higher than the equivalent amount, grape longan, non-nuclear purple, enamel and other varieties are prone to phytotoxicity. 4, Bordeaux mixture with stone sulphur mixture, antibacterial special, etc., or alternate use, the interval is too short, are easy to produce phytotoxicity. 5. Bordeaux mixture is used under high temperature conditions, which is easy to cause phytotoxicity caused by lime. After spraying, if the liquid is not dry, it will spray when the rain or the leaves are not dry. Due to the dissociation degree of copper and the change of the penetrating ability of the leaves, the content of soluble copper on the leaves will increase rapidly, causing the leaves to burn. After a period of use of Bordeaux liquid, if there is a large wind and rain, it will also increase the content of soluble copper on the leaf surface, causing the leaves to dry, causing so-called wind and rain damage. Second, measures to prevent the production of medicinal damage in Bordeaux mixture 1, to select the preparation of raw materials. When preparing Bordeaux liquid, high-quality, pure, white, light weight lump lime should be used. Copper sulfate should be blue crystal. If it is yellow or green powder, it should not be used. 2. Strictly follow the preparation procedure. In the dispensing, the copper sulfate is firstly opened in a non-metallic container with an appropriate amount of hot water, and then filtered, and 90% of the total amount of water is added, and after the opening, the residue is filtered off. Pour the filtered lime liquid (with 10% water) into a large tank or cement tank, then slowly pour the copper sulfate solution into the lime liquid in the tank or cement pool, and stir vigorously while pouring. Stirring is continued for another 2-3 minutes. Never pour the lime liquid into the copper sulfate solution, otherwise the prepared liquid will precipitate quickly and is prone to phytotoxicity. In addition, it is best to use the drug immediately after it is formulated. It should not be used for a long time. 3, pay attention to the spraying period. It is not advisable to use Bordeaux mixture within 1 month after the flower falls and when the fruit is nearing maturity, in order to prevent rust spots on the fruit surface or affect the coloration. When spraying a bactericide in this period, carbendazim, thiophanate or the like can be used. 4. Different tree species should use different concentration ratios. For nuclear fruit trees such as peach, apricot and plum which are particularly sensitive to copper ions, Bordeaux mixture cannot be used during the growing season. For other tree species, different formulations and ratios should be selected according to their sensitivity. For copper-sensitive tree species, lime type or multi-type can be used. For pear trees that are less sensitive to lime or copper, lime equivalents can be used. For grapes that are sensitive to lime and tolerant to copper, a half-size ratio of lime can be used. 5, a reasonable mix. Bordeaux mixture can not be mixed with stone sulfur, antibacterial and so on. Bordeaux mixture should be used with organic phosphorus pesticides carefully and can be used with mixing. It is only 10 days after spraying the stone sulphur mixture to spray the Bordeaux mixture. After spraying the Bordeaux mixture for 20-30 days, the stone sulphur mixture can be sprayed. 6. Pay attention to the changes in the weather. Spraying Bordeaux mixture should be done in a clear, dew-free time. Spraying in summer should avoid the high temperature noon, so as to avoid the damage of lime at high temperature. Spray in the rainy season, try to avoid the wind and rain, and at the same time, properly increase the amount and proportion of lime in the dispensing. The above is an introduction to the problem of Bordeaux liquid phytotoxicity. 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