VARIOUS INSECTICIDES 297 



trated 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 purpk. See under ARSENICALS, p. 291. 



Miscible oils. There are now on the market a number of prepara- 

 tions 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 cineraricefolium. 

 BUHACH, made in California from cultivated plants of Pyrethrum 

 cineraricefolium . 



When fresh and pure, all these brands appear to be equally val- 

 uable, 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. 



