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Bordeaux mixture(bôrdō`), fungicide consisting of cupric sulfatecupric sulfate
or copper (II) sulfate,
chemical compound, CuSO4, taking the form of white rhombohedral crystals or amorphous powder. It decomposes at 650°C; to cupric oxide (CuO).
..... Click the link for more information. and lime in water. Its fungicidal activity is associated with the slow formation of copper compounds, the ultimate toxicant being the cupric ion. It originated in France in 1885 and was widely used for spraying orchards, dusting crops, and treating seeds until c.1930. Since it was found that Bordeaux mixture frequently caused russeting of fruit, injured the leaves, and led to premature defoliation, it has been generally replaced by solutions made with powdered fixed copper. Sal soda Bordeaux, or Burgundy mixture, containing cupric sulfate and sodium carbonate (sal soda), was formerly used to spray small fruits but has been replaced by more convenient preparations. See pesticidepesticide,
biological, physical, or chemical agent used to kill plants or animals that are harmful to people; in practice, the term pesticide is often applied only to chemical agents.
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a widely distributed chemical used against fungous and bacterial diseases of plants.
Bordeaux mixture is prepared on the day of use. One kg of blue vitriol is dissolved in 90 liters (7) of water. While these ingredients are being mixed, 10 1 of freshly prepared milk of lime is added. This causes the precipitation of basic sulfuric salts of copper in the form of a gelatinous precipitate that covers the leaves and fruits of plants effectively.
Bordeaux mixture is used most frequently to prevent grapevine mildew, apple scab, pear scab, and spots on stone fruits. The period and quantity of application depends on the biological characteristics of the cause of the disease and on weather conditions. Plants are sprayed with a 3–5 percent Bordeaux mixture (blue spraying) until the buds open. At the time of vegetation, a 0.5–1 percent solution is used. Bordeaux mixture should not be acidic, or it will burn the leaves. It is slightly poisonous.