35 



It is therefore preferable to use stronger insecticides wliile the 

 trees are dormant in winter, and the best results are obtained by 

 spraying in February and March and even later, till the buds 

 begin to open. 



Fumigation. 

 For small trees which it is possible to cover with an air-tight 

 tent, fumigation is the most reliable treatment which can be used, 

 as the gas will reach all the insects when a spray would probably 

 fail to do this ; but the cost of a tent increases so rapidly with its 

 size that only small trees can profitably be treated in this way. In 

 the case of nursery stock, however, this is the best treatment to 

 make use of. Certain cases have been reported in which destruc- 

 tion of the scale by fumigation has apparently not been a success. 

 In every case, this seems to have been due to failure in properly 

 carrying out the directions for the work. Either the tent or box 

 used was not air-tight, or the potassic cyanide was of the 50 per 

 cent strength usually sold by druggists instead of the 98 per cent 

 or 99 per cent strength necessary, or the time during which the 

 fumigation was continued was not sufficient. Failure to meet any 

 one of these requirements would give a failure in the results. 



Sprayii^g. 



Of the many materials used for spraying for the San Jose scale 

 few are of much value, and none may be expected to destroy all 

 the scales, as some will in all probability fail to be touched. On 

 the thoroughness of the work, then, depends the success of the 

 treatment. 



If but a few trees are to be sprayed it is probable that potash 

 whale-oil soap will cause the least trouble to apply. At the Hatch 

 Experiment Station at Amherst several brands of this soap were 

 tested in 1902, and the best results were obtained with Bowker's 

 Tree Soap. Two pounds of this soap were dissolved in each 

 gallon of water used, and the solution was sprayed warm, using an 

 ordinary spray pump and a Vermorel nozzle with very small 

 opening, giving a fine mist. All parts of trunk and limbs were 

 covered by the spray, treatment of any portion being stopped 

 the moment the spray began to drip or run down the bark. 



Crude petroleum and kerosene were also used in the form of a 

 mechanical emulsion with water. This emulsion was produced by 

 the pump (Kerowater), which has two tanks, one for oil and one 

 for water, with a line of hose from each to the nozzle where the 

 two streams combine and are forced out together, the proportion 

 of each being regulated by attachments of the pistons to the pump 



