For a 10% emulsion add 17 gal. of water to 3 gal. stock emulsion.
For a 15% emulsion add 10 1/3 gal. of water to 3 gal. stock emulsion.
For a 20% emulsion add 7 gal. of water to 3 gal. stock emulsion.
For a 25% emulsion add 5 gal. of water to 3 gal. stock emulsion.
Carbolic acid emulsion.—Soap, 1 lb.; water, 1 gal.; crude carbolic acid, 1 pt. Dissolve the soap in hot water, add the carbolic acid, and agitate into an emulsion. For use against root-maggots, dilute with 30 parts of water.
Soaps.—An effective insecticide for plant-lice is whale-oil soap. Dissolve in hot water and dilute so as to obtain one pound of soap to every five or seven gallons of water. This strength is effective against plant-lice. It should be applied in stronger solutions, however, for scale insects. Home-made soaps and good laundry soaps, like Ivory soap, are often as effective as whale-oil soap.
Miscible oils.—There are now on the market a number of preparations of petroleum and other oils intended primarily for use against the San José scale. They mix readily with cold water and are immediately ready for use. While quickly prepared, easily applied, and generally effective, they cost considerably more than lime-sulfur wash. They are, however, less corrosive to the pumps and more agreeable to use. They are especially valuable to the man with only a few trees or shrubs who would not care to go to the trouble and expense to make up the lime-sulfur wash. They should be diluted with not more than 10 or 12 parts of water. Use only on dormant trees.
Lime and sulfur wash.—Quicklime, 20 lb.; flowers of sulfur, 15 lb.; water, 50 gal. The lime and sulfur must be thoroughly boiled. An iron kettle is often convenient for the work. Proceed as follows: Place the lime in the kettle. Add hot water gradually in sufficient quantity to produce the most rapid slaking of the lime. When the lime begins to slake, add the sulfur and stir together. If convenient, keep the mixture covered with burlap to save the heat. After slaking has ceased, add more water and boil the mixture one hour. As the sulfur goes into solution, a rich orange-red or dark green color will appear. After boiling sufficiently, add water to the required amount and strain into the spray tank. The wash is most effective when applied warm, but may be applied cold. If one has access to a steam boiler, boiling with steam is more convenient and satisfactory. Barrels may be used for holding the mixture, and the steam applied by running a pipe or rubber hose into the mixture. Proceed in the same way until the lime is slaked, when the steam may be turned on. Continue boiling for 45 min. to an hour, or until sulfur is dissolved.
This strength can be applied safely only when the trees are dormant. It is mainly an insecticide for San José scale, although it has considerable value as a fungicide.
Lime-sulfur mixtures and solutions for summer spraying are now coming to take the place of bordeaux in many cases. Scott’s self-boiled lime-sulfur mixture, described in U. S. D. A. Bureau Plant Industry Circ. 27 is now a standard fungicide for brown-rot and black-spot or scab of the peach. Concentrated lime-sulfur solutions, either home boiled or commercial, are effective against apple scab and have the advantage of not russeting the fruit. Such concentrates, testing 32° Baume, should be diluted at about 1 gal. to 30 of water. Apply at same time as with bordeaux. Add arsenate of lead as with bordeaux.
The standard fungicide is bordeaux mixture, made in several forms. The second most important fungicide for the home gardener is ammoniacal copper carbonate. Sulfur dust (flowers of sulfur) and liver of sulfur (potassium sulfide) are also useful in dry or wet sprays for surface mildews. The lime-sulfur wash, primarily an insecticide, also has fungicidal property.
Bordeaux mixture.—Copper sulfate, 5 lb.; stone lime or quicklime (unslaked), 5 lb.; water, 50 gal. This formula is the strength usually recommended. Stock mixtures of copper sulfate and lime are desirable. They are prepared in the following way:—