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Bordeaux mixture is compounded from lime and copper sulphate (bluestone) and its fungicidal value was discovered by chance over a hundred years ago near Bordeaux. Ready-mixed powder is cheap, and easy to dissolve and apply. The strength of the solution advised by the maker will vary with the season in which it is to be used, and will be found printed on the container. It does not keep well, and so some gardeners prefer to mix their own solution. Only glass, wooden, earthenware, or copper vessels should be used in preparing the mixture; never use iron or zinc ones. The necessary quantities will be one pound each of freshly burnt lime and copper sulphate. For winter spraying, ten gallons of water should be added; for summer spraying, twelve and a half gallons will be needed.

Copper sulphate is not as readily soluble as many people believe; wrap it in coarse hessian and suspend it just beneath the surface of two and a half gallons of water; leave it for twenty-four hours. Take the lime in another vessel and slake it by adding water, little by little; it will become very hot, and therefore great care must be taken if it is in a glass or earthenware vessel. When the lime is slaked, make up the volume to seven and a half gallons in winter or ten gallons in summer by adding water. Pour the two and a half gallons of copper sulphate solution into the milk of lime and stir thoroughly. Finely strain the mixture before pouring it into the sprayer, since any coarse particles may choke the spray nozzle, causing much loss of time and annoyance. Bordeaux mixture deteriorates quickly in liquid form, and so it should be used as soon as possible after mixing. It is incompatible with almost all other sprays, and is strongly alkaline.

Bordinette is much better than Bordeaux mixture in two ways, namely, it keeps well and it dissolves readily in cold water. It should be used in the strength of one pound to ten gallons of water, or twelve and a half gallons of water, according to the season.

Cuprox is another proprietary preparation, and a further improvement. Its active constituent is re-dispersible copper oxychloride. It is neither acid nor alkaline, and is compatible with wettable and colloidal sulphurs, E605, Lindane, DDT, and Chlorparacide.

Sulphur is available for use in many forms as sprays and dusts. The best of these are the wettable sulphur and colloidal sulphur proprietary preparations; they replace and excel lime-sulphur and flowers of sulphur. They are all used in mildew control, affecting the spores of the fungus.

Wettable and colloidal sulphurs, such as Wetsul and Sper-sul, are cheap, easily mixed with cold water, and are safe to use, except on very hot days, when all sulphur preparations are apt to cause scorching of the foliage. They are compatible with E605, Lindane, DDT, Chlorparacide, and preparations of copper oxychloride.

Lime sulphur is obtainable as a ready-mixed powder, but needs to be carefully strained before using, so as to avoid blocking of the spray nozzle. It has an unpleasant odour, and should never be sprayed on paint-work, for it will blacken it. Lime sulphur was discovered by accident in the early part of the nineteenth century. It is strongly alkaline, and is incompatible with all sprays except nicotine sulphate.

Flowers of sulphur were once a traditional preventive and curative for mildew. The powder is sprinkled over the plants, but its action depends on sulphur dioxide being made from it on the ground, and the fumes rising through the foliage. A calm day is necessary for several reasons-the powder and fumes are easily blown away, and the fine particles of sulphur are very irritating to one's eyes. Massey dust consists of nine parts of flowers of sulphur and one part of arsenate of lead powder. It combines the action of the two chemicals and is advocated overseas for control of black spot as well as mildew.

Shirlan for mildew control has one advantage over sulphur preparations in that it is safe to use on hot days, but otherwise it is not as good. Its active principle is a salicylanide with sulphonated organic matter.