Bordeaux mixture is an inorganic copper bactericide. It is a sky blue colloidal suspension made of about 500 grams of copper sulfate, 500 grams of hydrated lime and 50 kilograms of water. The proportion of ingredients can be increased or decreased as needed. Generally alkaline, with good adhesion, but the physical properties are destroyed after long-term storage. It is suitable to mix with existing or dehydrated Bordeaux powder and then mix with water when using.
The solution is a protective sterilization agent, which inhibits spore germination or mycelium growth of pathogenic bacteria by releasing soluble copper ions. Under acidic conditions, when a large amount of copper ions are released, it can also solidify the cell protoplasm of pathogenic bacteria and play a bactericidal role. When the relative humidity is high and there is dew or water film on the leaves, the drug effect is better, but it is easy to cause phytotoxicity to plants with poor copper tolerance. It has a long lasting period and is widely used to control many diseases such as vegetables, fruit trees, cotton and hemp. It is especially suitable for leaf diseases such as downy mildew, carbon disease and potato late blight.
Bordeaux mixture is a protective degerming agent. The effective component is basic copper sulfate, which can effectively prevent spore germination, prevent bacterial infection, promote dark green leaves and healthy growth, and improve the disease resistance of trees. The preparation has the characteristics of broad bactericidal spectrum, long duration, no drug resistance of bacteria, low toxicity to people and animals, etc. It is a sterilization agent with the longest application history.
Bordeaux mixture itself has no bactericidal effect. When it is sprayed on the surface of plants, it is adsorbed on the surface of crops because of its adhesion. In the process of metabolism, plants secrete acidic liquid. When bacteria invade plant cells, a small amount of basic copper sulfate in Bordeaux liquid will be converted into soluble copper sulfate, thus generating a small amount of copper ions, which will coagulate protein in the cells after entering germ cells. Copper ions can also destroy some enzymes in its cells, thus making the metabolism in bacteria unable to proceed normally. Under these two effects, bacteria will die.
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To prevent and control early defoliation, carbon disease and ring rot of apples, 200-240 times of lime Bordeaux solution can be sprayed once every two months after apples fall, and it can be used alternately with other fungicides for 3-4 times. In order to prevent and control apple rot (ring rot and carbon rot), 200 times lime double or multiple doses of Bordeaux solution 1 time can be sprayed every 15 days 20 days before the appearance of diseased fruits in previous years, and it can be stopped 25 days before the fruit is harvested. To prevent and control apple mould heart disease, 200 times of lime Bordeaux solution should be sprayed at the bud stage of apple. In order to prevent the rust of apples and pears, we can spray 160 times of Bordeaux solution and the same amount of lime on juniper trees around the apple orchard. A small amount of bordeaux lime 160 times can be sprayed every 12 ~ 15 days, 2 ~ 4 times, to prevent and control grape black disease, charcoal disease and downy mildew. After the rainy season, it is effective to use Bordeaux mixture to control grape diseases.