286 Kepout of the Departmeint of Entomology of the 



all 4483 buds were treated 78 per ct. of which set. The checks 

 numbered 4864 of which 85.5 per ct. set, thus making but a slight 

 difference in favor of the checks, a difference which might be 

 expected from the unusual exposure of the treated buds. 



The experiments with the scale gave somewhat unexpected 

 results in that the scales were practically unaffected by winter 

 fumigation with the gas at a strength less than .3 gram of 

 cyanide per cubic foot of air space. This result has an important 

 bearing upon the winter fumigation of nursery stock. To be 

 certain of killing the hibernating scales in this latitude the gas 

 should be used at the above strength.^ 



The spring treatment gave different results. The gas at ,a 

 little more than half the strength (.18 gram) killed the scales in 

 every case and did not injure the foliage. 



RECOMMENDATIONS. 



Obviously the first step in combating the San Jos^ scale is to 

 prevent infestation. As the most fruitful source of infestation is 

 nursery stock it is plainly of the greatest importance to prevent 

 the spread of infested stock. Fumigation with hydrocyanic acid 

 gas together with careful inspection and clean cultivation are 

 our best safeguards. If stock is to be fumigated too much pains 

 cannot be taken to have all conditions right for thorough work. 

 Above all else the fumigating house should be gas tight. For 

 winter fumigation the gas should be used at a strength of .3 

 gram of cyanide. For early spring treatment a strength of .18 

 to .2 gram of cyanide will be sufiicient to kill the scales. 



An additional safeguard in the nursery is the fumigation of 

 bud sticks, scions, etc., especially if such stock has been brought 

 from infested localities. The gas at a strength of .22 gram of 

 cyanide can be safely used on the common varieties of fruits and 

 probably all varieties without danger of injury. 



Tor directions for computing the amount of cyanide to use for a given 

 number of cubic feet of air space see Bulletin No. 104 of this Station, 

 p. 382. 



