250 MASS. EXPERIMENT STATION BULLETIN 170. 



Besides the larger spraying enterprises which are being carried on for 

 the suppression of the gypsy and brown-tail moths, much private work 

 is being done, and hundreds of tons of arsenate of lead are used annually 

 in this work. While the above-named pests have not at present invaded 

 the central and western parts of the State to any extent, other pests ne- 

 cessitate spraying our shade trees. 



For years a great deal of attention has been given to the improvement 

 of spraying machines, nozzles, etc. It has often been a question whether 

 our towns of cities can afford to use the methods which are recommended 

 and practiced by the best orchardists for shade trees. The aim of the 

 orchardists is to cover every part of the tree which needs protection with 

 a very fine mist spray. This method cannot be too closely followed by 

 orchardists, since it is not necessarily expensive when only orchard trees 

 and small fruits and crops, such as potatoes, are concerned. However 



FIG. 106. Large spraying equipment. 



when we have to spray large elms, the question becomes an entirely 

 different one. 



A few years ago some large elms located in the public square in one of 

 our cities were sprayed by the same methods used by the best orchardists, 

 at an expense of something like $16 per tree. These trees, to be sure, were 

 unusually large, but the cost was so great that in our opinion it set a limit 

 to the amount of spraying which should be undertaken by such methods. 

 Most of the former spraying of shade trees was done by this very expen- 

 sive method at a cost of $1.50 upwards for trees 14 to 18 inches in diameter. 

 In much of this early spraying the Vermorel, Ware or similar fine-spray 

 nozzles on poles were used, and spraying had to be done at close range for 

 the best results. The early gypsy moth work was done in this same way, 

 any other method at that time being considered useless. This method 

 entailed a great deal of climbing on the part of the sprayers, and was a 

 slow and costly process. With the improvement of gasoline engines, 



