DIPPING AND FUMIGATION OF NURSERY STOCK 



15 



dead and live insects counted. From these numbers, the percentage of live 

 insects was determined. On May 25, 1916, additional counts were made and 

 on May 26, 1916, the number of trees which were dead was counted. 



The results obtained show clearly that hydrocyanic-acid gas used at 

 the strength of 1-1-3 and %-%-!% will kill San Jose scale on dry plants 

 better than on moist plants. Also the dry plants suffered more from the 

 treatment than the wet ones. The hydrocyanic acid gas gave best results 

 when used at the rate of 1-1-3 upon dry trees. Upon the other three sets 

 live scales were found, the larger percentage being upon the trees treated 

 while damp. All of these trees were heavily infested with the scale at the 

 time of treating and their vitality had been weakened a great deal and this 

 is undoubtedly the reason why such a large percentage died. The normal 

 mortality of scale on the check trees was 38.9 per cent and the high mor- 

 tality of the trees was undoubtedly due to the effects of the pest. 



On April 9, 1917, the following trees were treated with hydrocyanic 

 acid gas, 1-1-3. 



TABLE 2. APPLES TREATED IN 1917 



This test in 1917 was made in order to check or substantiate the results 

 obtained in 1916. On April 20, 1917, the trees were thoroly examined for 

 scale and no live scale whatsoever could be found on either the trees wet 

 or dry. In comparing the above treatments with the check it is clearly 

 shown that good results were obtained with hydrocyanic-acid gas used at 

 the rate of 1-1-3. 



On March 22, 1920, additional experiments were performed with HCN 

 as is shown by the following table. 



TABLE 3. APPLES TREATED IN 1920 



this treatment Sodium cyanide (NaCN') was used. 



