158 PRINCIPLES OF PLANT CULTURE 



compounds on plants or fruits which are to be used soon 

 after the poison is applied. Hellebore is frequently 

 used, therefore, against such insects as the imported 

 currant worm and the cabbage caterpillar. 



Hellebore powder, when used dry, may be diluted with 

 once or twice its bulk of flour, which causes it to adhere 

 better to the foliage than if used alone. When applied 

 with water, a heaping teaspoonful or more may be added 

 to three gallons. The dry powder is very light and 

 should only be used in a still atmosphere. 



A decoction made by boiling the root of white helle- 

 bore in water is said to possess insecticide properties 

 similar to those of the powder. 



290. Pyrethrum powder (Persian insect powder, Dal- 

 matian insect powder, Buhach) is the pulverized flowers 

 of certain species of Pyrethrum. 1 Pyrethrum powder 

 is not poisonous to the higher animals, but the oil that 

 pervades it is destructive to many insects. As the oil 

 is extremely volatile, pyrethrum is better adapted for 

 use under glass or with plants otherwise inclosed. It is 

 not injurious to foliage or flowers. Fresh and pure 

 pyrethrum powder may be diluted half or more in bulk 

 with any other light, cheap, harmless powder, but the 

 mixture should stand a day or two before use, to enable 

 the diluent to absorb the oil. The powder may be used 

 with water at the rate of half a pound to three gallons. 



The pyrethrum plant is comparatively hardy and has 

 been successfully grown in northern United States. It 



1 "Persian insect powder" is made from the flowers of 

 Pyrethrum roseum&nd P. carneum; "Dalmatian insect powder" 

 and "Buhach" are made from those of P. cineraiaefolium. 

 "Buhach" is the trade name of a pure product prepared in 

 California. 



