10 HORTICULTURIST'S RULE-BOOK. 



Paris green. See under ARSENITES. 



Persian insect powder. See PYRETHRUM. 



Plaster and kerosene. 2 quarts of plaster or wood ashes, 

 1 tablespoonful of kerosene. Mix, and rub with the hands 

 until the oil is well incorporated. Bone-flour may be sub- 

 stituted for the plaster. Repellent ; used mostly for flea- 

 beetles and striped squash-beetles. 



Plaster and turpentine. 2 quarts common land plaster, 1 

 or 2 tablespoonf uls of turpentine, mixed and used as in the 

 preceding. 



Potash. Kainit, 1 ounce to a pint of water, applied in a 

 spray, is recommended for aphis and various leaf-eating 

 larvae. Muriate of potash, applied in the same strength, is 

 as good, but is more likely to injure the plants. Rarely 

 used. 



Potassic fertilizers have been recommended as insecti- 

 cides against various ground insects. 



Promoting growth. Any course that tends to promote vigor 

 will be helpful in enabling plants to withstand the attacks 

 of plant-lice and other insects. 



Fyrethrum. 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 upon 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. 

 DALMATIAN INSECT-POWDER, made from Pyrethrum cinerar- 



icefolium. 



BUHACH, made in California from cultivated plants of P. 

 cineraricefolium. 



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. 



2. Dry, without dilution. In this form it is excellent for 



