Commissioner of Agriculture, 117 



mixing pump, will keep the scale in check in orchard trees, and 

 may possibly exterminate it. 



Many experiments in the fumigation of orchard trees with 

 hydrocyanic acid gas have been made, and in most cases show 

 that a single fumigation killed every scale, as none appeared 

 the season following. However, there are instances where live 

 scales appeared on the fumigated trees during the following 

 breeding season. The fact that scales can all be killed, but are 

 not, shows a fault somewhere. It may be that the chemicals 

 used were not up to the standard of purity, that they were not 

 properly mixed, that the tent was not air-tight, that the cubic 

 feet of space was not rightly proportioned to the cyanide used, 

 or that the exposure was inadequate. Then, too, live scales 

 may come from adjoining trees. 



Here we have two methods that promise to help the unfortu- 

 nate orchardist. Both can be used to advantage, and neither 

 will injure the trees. Small orchard trees can be treated at 

 about the same cost by either method, but tents for large trees 

 are expensive; therefore there seems no other way left than to 

 spray. The use of petroleum, where it has been effective in 

 checking the scale, was applied as late in spring as possible, 

 prior to the flow of sap or the opening of the buds. The light- 

 colored amber oils of a light specific gravity, used with a mixing 

 pump at the rate of 25 per cent of oil to 75 per cent of water, 

 seems to be the best formula at present known. 



The best results obtained by hydrocyanic acid gas have been 

 where the work was properly done in every detail, and the 

 formula for generating the gas was as follows : 1 ounce of cyan- 

 ide of potassium, 98 per cent pure; H ounce of commercial 

 sulphuric acid and 3 ounces of water to each 100 cubic feet of 

 space, with 30 to 45 minutes' exposure. 



Twelve hundred and eleven orchard trees and 26,296 currant 

 bushes were destroyed because of the San Jose" scale. In many 

 orchards, apple canker is getting in its destructive work; 

 black-knot is locally bad; borers and bark beetles, blight, apple 

 scab and scale insects other than San Jose' are frequently found 



