152 Insect Pests. 



This ground treatment must be carried out before April, and in 

 dry u-eather. The effect in wet soil is, I have found, as disappointing 

 as it is satisfactory in dry land. Mr. Pickering informs me this 

 cannot be so, as it should be most fatal in damp soil. However, 

 personal experience has proved the reverse two years in succession. 



It is very essential that all young stock be fumigated with hydro- 

 cyanic acid gas before planting. The stocks may be placed in a 

 greenhouse or tent rigged for the purpose, of known capacity, and then 

 fumigated. When dormant, as at the time of lifting, the bushes may 

 be fumigated at the following strength : For every 100 cubic feet of 



[A. V. D. JRintoul. 

 FIO. 126. INJECTING BISULPHIDE OF CARBON BY MEANS OF THE VERMOREL INJECTOR. 



space use 1 oz. of sodium cyanide or potassium cyanide, 1 oz. of sul- 

 phuric acid and 4 oz. of water. The trees should be kept in the 

 fumes for 45 minutes. It will be found that the tips may now and 

 then be scorched, especially in some varieties, as the Beauty of Bath 

 and Worcester Pearmain, but no actual damage is done. If nursery- 

 men will not guarantee the stock has been so treated, then it is well 

 worth the grower's while to do so himself.* 



* Pickering recommends immersion in petrol for five minutes or in water at 

 115 F. for ten minutes. This kills the aphis, but neither, as far as I can see, 

 affects the ova, so that fumigation had best be relied on. 



