1908.] PUBLIC DOCUMENT- -No. 73. 141 



opinion, based upon a somewhat extended experience. It is 

 perfectly true that no two spraying problems present exactly 

 the same conditions. The presence or absence of roads, the dis- 

 tance from the sprayer to the point to which the stream must 

 be carried, the contour of the ground, height of the trees, abun- 

 dance or scarcity of underbrush, and the distance from which 

 water must be pumped or hauled to supply the sprayer, are a 

 part of the many details which must be taken into considera- 

 tion in estimating costs of work. Again, the type of outfit with 

 reference to the manner of obtaining power is of importance. 

 The three styles of rigs in general use in the gypsy moth dis- 

 trict include those operated by hand, by gas or compressed air, 

 and by gasoline engines. Each kind of outfit has its own field 

 of usefulness, and each has its ardent champions. Still, again, 

 the kind of spray used, whether the mist or solid stream, greatly 

 affects the cost of spraying. 



It seemed desirable this summer to get careful data on the 

 actual cost of spraying operations in the field, and Mr. A. F. 

 Burgess, assisted by Mr. C. G. Barnum, was especially assigned 

 to this work. The data which follow are condensed from Mr. 

 Burgess's very complete field notes : - 



WATERTOWN, WHITNEY HILL PARK, JUNE 11, 12, 1907. 



On the steep hillside in this park 7 acres of large forest trees, viz., 

 oak, hickory and beech, were sprayed with one of the outfits belonging 

 to the United States Department of Agriculture. Although the cater- 

 pillars were less than half grown, the effect of their feeding was very 

 noticeable. About 600 trees, averaging 1 60 feet in height, were treated. 

 In the twelve hours required to make this spraying, considerable time 

 was lost in moving the sprayer. "Water was obtained from the city 

 hydrants. Work was begun at the top of the hill, and but very few 

 of the trees were climbed. June 11, 8 tanks, and June 12, 5 tanks of 

 spray were used, the total amount applied being 7,800 gallons. 



Outfit. 



The outfit consisted of a 7 horse-power Olds engine, with double- 

 acting pump and a 600-gallon tank. One 200-foot line of IVo-inch 

 hose and a %-inch nozzle Avere used, the pressure averaging 130 pounds. 

 The insecticide was Swift's arsenate of lead, applied at the rate of 10 

 pounds to 100 gallons of water. 



