Plants as Affected by Animal Parasites. 153 
When used dry, hellebore powder 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 hellebore 
in water is said to possess insecticide properties similar to 
those of the powder. 
290. Pyrethrum (py-re’-thrum) Powder, (Persian 
insect powder, Dalmatian insect powder, Buhach) is the pul- 
verized flowers of certain species of Pyrethrum.* 
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. When fresh and pure, 
pyrethrum powder may be diluted half or more in bulk with 
any other light and 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 is 
said that a decoction of the unopened flowers possesses the 
insecticide properties of the commercial product. 
291. MHellebore and Pyrethrum Powders should be 
Kept in Close Vessels, since their poisonous properties are 
* “ Persian insect powder” is made from the flowers of Pyrethrum roseum, and 
P. corneum; “Dalmatian insect powder” and ‘‘ Buhach”’ are made from those of 
P. cineraiefolium. ‘‘ Buhach” is the trade name of a pure product prepared in 
California. 
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