PROCEEDINGS, 1918 71 



insecticide alone. Per arsenic content it is quite expensive 

 compared with several other arsenicals, and consequently in 

 such combinations with fungicides as render other arsenicals 

 safe it is not to the best advantage to use lead arsenate. 



In Nova Scotia lead arsenate is used particularly for the 

 control of cankerworms and for other sporadic outbreaks such 

 as the Tussock caterpillar. It is used to some extent in com- 

 bination sprays, though it is giving place in this respect to 

 cheaper arsenicals. 



Arsenate of Lime. 



Arsenate of lime is of comparatively recent origin. It 

 came to light as a result of continuous search for a cheaper base 

 with which to unite arsenic acid, which at the same time would 

 result in a product of something like equal stability to lead 

 arsenate. The U.S. Bureau of Entomology experimented with 

 it in 1912, and in succeeding years. Later it was taken up ex- 

 tensively in Nova Scotia, and experimentally in other places. 



At the present time arsenate of lime is just commencing to 

 be generally known, and its use is being rapidly increased. Used 

 alone it is under some conditions liable to burn foliage, but 

 used in combination sprays with Bordeaux mixture or lime sul- 

 phur, it is as safe as any known arsenical. In sodium sulphide 

 ("soluble sulphur", "sulfocide") sprays it is much the safest of 

 all arsenicals. It adheres fairly well to foliage, and remains 

 readily in suspension in water. At the present time it is the 

 cheapest of all insecticides for use in combination sprays, tak- 

 ing into consideration its safety. 



In Nova Scotia arsenate of lime is probably used more 

 proportionately than in any other place. It is being used 

 through the orcharding district with Bordeaux mixture and 

 sulphide sprays almost to the exclusion of other insecticides. 

 It is also used to some extent on the potato. 



Arsenate of Soda. 



Arsenate of soda first came into prominence, with the use 

 of lead arsenate. In Massachusetts,in 1892, before the legis- 

 lative joint standing committee on agriculture, a bill for the 

 destruction of caterpillars was considered. At this hearing- 

 Mr. A. H. Ward proposed the use of arsenate of soda. A sam- 

 ple was procured and tried on foliage with the result that the 

 foliage was burned. Following this Mr. Moulton proposed the 



