Bordeaux mixture is the broad-spectrum protective pesticide fungicide that has the longest application time in fruit trees, the widest application field, the most potent drug efficacy, and has not yet developed resistance. Its active ingredient is basic copper sulfate. In the production practice, some fruit farmers often cause phytotoxicity caused by improper preparation or use, and should be paid attention to and prevent.
First, the cause of the phytotoxicity of Bordeaux mixture 1. When preparing Bordeaux mixture, the dissolution of copper sulphate is not complete. When the medicine is sprayed on the fruit together with the dregs, the fruit will appear reddish brown and freckles, and the commercial value of the fruit will be reduced.
2. The use of Bordeaux mixture in the young fruit stage and the ripening of the fruit will cause rust spots on the fruit surface, rough skin and reduced smoothness, resulting in a decrease in the appearance 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. Because of the dissociation of copper and the change of leaf penetration, the content of soluble copper on the leaves will increase rapidly, causing the leaves to burn. After a period of use of Bordeaux liquid, in the case of large wind and rain, the content of soluble copper on the leaf surface will increase rapidly, causing the leaves to dry up, causing so-called wind and rain damage.
Second, the prevention of Bordeaux liquid production of phytotoxicity, the pesticide network is compiled as follows:
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, majestic compliance with the preparation process. In the dispensing, the copper sulfate is firstly opened in a non-metallic container with an appropriate amount of hot water, and then filtered, 90% of the total water is added, and the residue is filtered off after being opened. Pour the filtered lime liquid (with 10% water) into a large tank or cement tank, and then slowly pour the copper sulfate solution into the lime liquid in the tank or cement pool, and stir it while pouring. Stirring is continued for another 2-3 minutes. It is absolutely impossible to pour the lime liquid into the copper sulfate solution, otherwise the prepared liquid will accumulate quickly and is prone to phytotoxicity. In addition, it is best to use the liquid 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 close to maturity, in order to prevent rust 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 adopt 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 mixture, antibacterial and so on. Care should be taken when mixing Bordeaux mixture with organophosphorus pesticides. 10 days after spraying the stone sulphur mixture, the ability to spray Bordeaux mixture, after spraying the Bordeaux mixture for 20-30 days, the ability to spray the stone sulphur mixture.
6. Keep an eye on the changes in the weather. Spraying Bordeaux mixture should be done in a clear, dew-free time. Spraying in the summer should avoid the high temperature at noon, so that the lime does not cause phytotoxicity at high temperatures. In addition, the Chinese pesticide network warm reminder, spray in the rainy season, we should try to avoid the weather and weather, and at the same time, the dosage and proportion of lime should be properly increased when dispensing.
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