146 HORTICULTURAL MANUAL. 



we do not now consider these insects as any serious obstacle 

 in the way of successful apple- grow ing, and we cannot see 

 any reason why the remedy might not be successfully used 

 on garden insects and on the grasshopper, cotton-worm, 

 army-worm, Hessian-fly, and chinch-bug. One man with 

 a driver and team can sprinkle twenty acres in a day for 

 protection against any of these insects."* 



But some entomologists yet prefer the Paris green, 

 London purple, or other forms of the arsenites. The 

 reasons given are that they are safer and less liable to burn 

 the foliage than pure arsenic. But the writer can see 

 little force in this argument, as John N. Dixon and others 

 have found that one pound of white arsenic to four 

 hundred gallons of water will do the work with the canker- 

 worm, codling-moth, strawberry- worm, and tent-cater- 

 pillar, and this will not harm the tenderest foliage. 



Until recently entomologists have not favored the use 

 of pure arsenic, but the Paris green and London purple 

 are so variable in quality as sold by druggists, and white 

 arsenic is relatively so pure, that definite proportions can 

 easily be secured. So a change in opinion is now evident 

 in several States. At this time the spraying calendars 

 give such statements as that of Professor Summers, who 

 says: " As white arsenic, as found in the market, is little 

 liable to adulteration, this insecticide is less liable to vary 

 in strength than Paris green. The cost of materials is 

 also somewhat less, and when an arsenite is to be used in 

 such large amounts that the trouble of preparing is not 

 an important item we strongly recommend the use of this 

 compound." But lime or sal soda is now used in solution 

 with the arsenic. This changes the color of the stock 



* Premium essay by Hon. J. N. Dixon, published in Iowa Horti- 

 cultural Iteport, 1882. 



