PROTECTING PLANTS 193 



Insecticide spraying formulas. 



The two classes of insecticides are here described, — the 

 poisons (arsenicals and white hellebore) for chewing insects, as 

 the beetles and all kinds of worms; the contact insecticides, as 

 kerosene, oils, soap, tobacco, lime-sulfur, for plant-lice, scale, 

 and insects in such position that the material cannot be fed to 

 them (as maggots in the underground parts). 



Paris green. — The standard insecticidal poison. This is used in 

 varying strengths, depending on the insect to be controlled and the 

 kind of plant treated. Mix the Paris green into a paste and then add 

 to the water. Keep the mixture thoroughly agitated while spraying. 

 If for use on fruit trees, add 1 lb. of quick lime for every pound of Paris 

 green to prevent burning the foliage. For potatoes it is frequently 

 used alone, but it is much safer to use the lime. Paris green and 

 bordeaux mixture may be combined without lessening the value of 

 either, and the caustic action of the arsenic is prevented. The propor- 

 tion of the poison to use is given under the various insects discussed in 

 the succeeding pages. 



Arsenate of lead. ■ — This can be applied in a stronger mixture than 

 other arsenical poisons without injuring the foliage. It is, therefore, 

 much used against beetles and other insects that are hard to poison, 

 as elm-leaf beetle and canker-worm. It comes as a paste or a powder, 

 and should be mixed thoroughly with a small quantity of water before 

 placing in the sprayer, else the nozzles will clog. Arsenate of lead and 

 bordeaux mixture or lime-sulfur can be combined without lessening 

 the value of either. It is used in strengths varying from 4 to 10 lb. 

 per 100 gal., depending on the kind of insect to be killed. 



Arsenite of soda and arsenite of lime are sometimes used with bor- 

 deaux mixture. 



White Hellebore. — For wet application, use fresh white hellebore, 

 4 oz.; water, 2 or 3 gal. For dry application, use hellebore, 1 lb.; 

 flour or air-slaked lime, 5 lb. This is a yellowish white powder made 

 from the roots of the white hellebore plant. It loses its strength after 

 a time and should be used fresh. It is used as a substitute for the 



