Bordeaux mixture is a sky-blue viscous suspension made of copper sulphate, quicklime and water. It is alkaline and corrosive to metals. It is a non-systemic protective inorganic bactericide . Its active ingredient is basic copper sulphate. After spraying, it adheres to the surface of the crop and the surface of the bacteria in particulate form. It is transported by air, moisture, carbon dioxide and crops and pathogens. The role of other factors, slowly converted into soluble copper and play a bactericidal effect. Bordeaux liquid precipitates for a long time, and the crystallization gradually decreases. Therefore, it should be used now and cannot be stored. Bordeaux mixture can prevent cotton, peanut, rapeseed, broad bean, vegetable and fruit tree diseases. Because of its good adhesion, it is not easy to be washed away by rainwater on plants. It is simple in preparation, low in cost and popular among farmers, but improperly formulated. But it is counterproductive.

1, material selection

The quality of Bordeaux's liquid is closely related to the quality of raw materials, in addition to the preparation method. Commercially available copper sulfate has little difference in quality, and the difference in quicklime is very large. It should be used to fully burn out the ash block with no impurity density. The wet or weathered powdered lime is generally not used. If there is no quicklime instead of slaked lime, the dosage should be increased. -50%. Water should use rivers, rivers, lakes and ponds. The high temperature will cause the condensed precipitation of Bordeaux liquid colloidal particles. It is also not suitable to use hot water and heavier chloride-containing water during preparation to prevent phytotoxicity.

2, preparation

The method of preparation generally adopts the "two-liquid method". That is, the copper sulfate and the quicklime are respectively dissolved in two containers with a half amount of water, and then the copper sulfate and the quicklime are simultaneously poured into the third container, and the stick is gently stirred in one direction with the wooden stick until the liquid is in the sky blue. . It is also possible to use 90% of water for dissolving copper sulphate, 10% of water for blending lime milk, and then slowly pouring copper sulphate into the milk of lime, which is available in sky blue. The Bordeaux mixture prepared by these two methods has good suspension performance, fine particles, and is not easy to precipitate, and has strong adhesion on crops and good disease prevention effect. Never put the lime milk into the copper sulfate, otherwise the colloidal particles of the Bordeaux mixture will become thicker and easier to precipitate. In addition, the preparation of Bordeaux liquid can not use metal utensils, the application of porcelain cylinders or wooden barrels, plastic barrels, used sprayers should be washed immediately.

The ratio of ingredients to be formulated in various formulations of Bordeaux mixture should be determined by the sensitivity of the crop to copper sulphate and quicklime, and to what disease, season and temperature. In general, the more lime is used, the safer the plant, the longer the effect, but the slower the bactericidal effect. If the amount of lime is small and the bactericidal effect is fast, it is prone to phytotoxicity and can only be used on crops with strong copper resistance.

There are several blending amounts for the preparation of Bordeaux mixture, and the amount of blending should be determined according to the crop and the type of disease. Generally, there are various types such as "equal amount", "half amount", and "multiple type".

3, the best spraying period

Bordeaux mixture is a protective fungicide and should be applied before the onset of the disease (this will be ignored by many people) or at the onset of the disease. The longer the onset time, the worse the application effect. The flowering period of the crop, the morning dew is not dry, the weather is damp, and it is easy to produce phytotoxicity after spraying on a foggy day. When it is raining after spraying, it should be sprayed after the weather. Application should also be avoided at noon on sunny days when the temperature exceeds 30 °C.

Bordeaux mixture has a residual effect of more than 15 days due to its strong adhesion. Fruits and vegetables cannot be applied 15-20 days before harvest to avoid pollution. In addition, alkaline pesticides such as stone sulphur mixture should not be applied within 15-20 days of application of Bordeaux mixture, otherwise it may cause phytotoxicity; while spraying sulphur sulphur mixture requires more than 10 days to spray Bordeaux mixture. Mixed with Fushuangmei and Detoxification may cause phytotoxicity; mixing with cypermethrin will be ineffective. Mixed with other organophosphorus pesticides should be used with the use, not for a long time. Prepare the Bordeaux mixture and do not dilute with water when using it.

4, avoid spraying crops

Some crops are susceptible to susceptibility to copper ions or lime and should not be used. Crops sensitive to copper ions include apples, pears, Chinese cabbage, and wheat. Sensitive to lime, there are Solanaceae, Cucurbitaceae, potatoes, grapes, melons, etc., should use different amounts of compounding to reduce the role of phytotoxic factors. In the case of high temperature and drought, lime sensitive crops are particularly susceptible to phytotoxicity. It is not suitable for peach, plum, plum, apricot, Chinese pear, Chinese cabbage, kidney bean, lettuce, soybean, wheat, etc.

Bordeaux mixture is toxic to silkworms and should not be used on mulberry trees. Other young crops are also weaker in copper resistance and should be used with caution.

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