Dilutions of Concentrated Lime-Sulfur Solutions for Spraying

(N. Y. Exp. Sta.)

Insecticidal Substances Part 4 121

3. Commercial concentrated mixtures.

The lime-sulfur may be purchased in the concentrated form and the trouble of making it avoided. The strength of the commercial product varies considerably, and in order to compute the proper dilution correctly the strength should be determined by means of a hydrometer. Having determined the strength of the concentrated mixture, the proper dilution for use against the San Jose scale and blister mite may be obtained from the table on opposite page. 4. Self-boiled. See page 257.

London purple. — See under Arsenicals, p. 291.

Miscible oils.— There are now on the market a number of preparations of petroleum and other oils intended primarily for use against the San Jose 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, and when the temperature is above freezing and the trees are not wet.

Paraffine oil. — Essentially the same as Kerosene, which see (p. 294).

Paris green. — See under Arsenicals, p. 291.

Persian insect powder. — See Pyrethrum.

Pyrethrum. — A very fine and light brown powder, made from the flower-heads of species of pyrethrum. It is scarcely injurious to man. Three brands are on the market : — Persian Insect-powder, made from the heads of Pyrethrum roseum, a species also cultivated as an ornamental plant. The plant is native to the Caucasus region. Delmation Insect-powder, made from Pyrethrum cinerariaefolium. Buhach, made in California from cultivated plants of Pyrethrum cinerariaefolium.

When fresh and pure, all these brands appear to be equally valuable, but the home-grown product is usually considered most reliable. Pyrethrum soon loses its value when exposed to the air. It is used in various ways : —

1.  In solution in water, 1 ounce to 3 gallons. Should be mixed up twenty-four hours before using.

2.  Dry, without dilution. In this form it is excellent for thrips and lice on roses and other bushes. Apply when the bush is wet. Useful for aphis on house plants.

3.  Dry, diluted with flour or any light and fine powder. The poison may be used in the proportion of 1 part to from 6 to 30 of the diluent.

4.  In fumigation. It may be scattered directly upon coals, or made into small balls by wetting and molding with the hands and then set upon coals. This is a desirable way of dealing with mosquitoes and flies.

5.  In alcohol. (1) Put a part of pyrethrum (buhach) and 4 parts alcohol, by weight, in any tight vessel. Shake occasionally, and after eight days filter. Apply with an atomizer. Excellent for greenhouse pests. For some plants it needs to be diluted a little. (2) Dissolve about 4 ounces of powder in 1 gill of alcohol, and add 12 gallons of water.

6.  Decoction. Whole flower-heads are treated to boiling water, and the liquid is covered to prevent evaporation. Boiling the liquid destroys its value.

Good insect-powder can be made from Pyrethrum roseum, and probably also from P. cinerariaefolium, grown in the home garden. Resin and fish-oil compound. — Ten pounds of resin ; 11/2 pounds of fish-oil, 3 pounds of caustic soda, and enough water to make 50 gallons.

Break the resin into small lumps, and place it together with the caustic soda in the boiler, with three or four inches of water. Stir till the resin is dissolved; then add about one-fourth of the required water and boil one-half hour. Place in the spray tank and add the rest of the water.