No. 4.] INSECTICIDES. 365 



holding the bag over the potato hills, at the same time 

 striking the rod with a short stick held in the other hand. 

 Sometimes burning of the foliage results from this treat- 

 ment, and if used on a windy day there is presumably more 

 or less danger to the operator from poisoning. Another 

 excellent method for using the poison on low-growing plants 

 consists in mixing one part Paris green with thirty to fifty 

 parts plaster, ashes, or, perhaps best of all, wheat-middlings, 

 applying the mixture to the plants by means of a sieve early 

 in the morning before the dew has dried off. This forms a 

 slight paste which causes the poison to adhere to the foliage 

 for a considerable period. Probably the oldest and most 

 common method of application to both plants and trees is 

 the mixture of Paris green suspended in water and applied 

 as a spray. This method, like the others, does not eliminate 

 the danger of burning the leaves when the mixture is too 

 strong, but to do the most effective work it is good policy 

 to use the mixture as strong as possible without causing 

 serious injury to the foliage. Experiments have shown the 

 average burning point to be below the proportion of one 

 pound of Paris green to one hundred and fifty gallons of 

 water. The addition of lime to the mixture is recommended 

 by some entomologists. This is thought to neutralize the 

 small amount of free arsenious acid in the Paris green, thus 

 preventing in some degree the danger of burning the foliage. 

 Care must be taken, however, not to add too great a quan- 

 tity of lime, nor allow the mixture to stand for any consider- 

 able period of time, since otherwise a more soluble compound 

 and one of greater burning powers will be formed. 



Arsenate of Lead. 

 This new insecticide, which was discovered by Mr. F. C. 

 Moulton while experimenting under the direction of the 

 State Board of Agriculture in connection with the work of 

 exterminating the gypsy moth, has proved so far to be the 

 best of any of the arsenical compounds. It may be pre- 

 pared by mixing approximately thirty parts by weight of 

 arsenate of soda dissolved in water with seventy parts ace- 

 tate of lead also dissolved in water. As a result of the 



