INSECT PESTS OF OHIO SHADE AND FOREST TREES 187 



Hand-driven mist sprayers. The earlier machines used for 

 spraying in park and shade-tree work were, of course, the hand- 

 driven types, such as the examples shown in Plate VII, Figs. 1 and 

 2, but long ago the hand-driven pumps were relegated in favor of 

 the power-driven ones. For many reasons the field of usefulness 

 of the former is greatly restricted and rarely today can they be 

 employed to advantage, except perhaps in the spraying of shrubs, 

 in nursery work or in treating small trees not easily accessible to 

 the power sprayer. Experience has taught that the saving made 

 by the lower original cost of the smaller machine is quickly obscured 

 by the greater cost of operation in applying the large quantities of 

 spraying material required in the treatment of large trees. Thus 

 the superiority of the power-driven machine for the purpose, at 

 hand has been fully demonstrated, not only with regard to the cost 

 of the operation but in the efficiency of the work as well, and it 

 scarcely seems worth while to devote further space to the discussion 

 of the hand types. 



The power-driven mist sprayers. Only the larger, better-built 

 power sprayers survive the usage and hardships to which the city 

 spraying machine is subjected; hence the greatest of care should 

 be exercised in selecting the make and type to be used. Capacity, 

 simplicity, durability and a suitable equipment of accessories, as 

 pointed out in the publications previously referred to (Buls. 216 and 

 248, .Ohio Agr. Exp. Sta.) are all highly essential general features 

 which the machine should embody. 



In detail, the specifications of a modern power mist sprayer 

 best suited for general city spraying may be given as follows: 



Pump. Capacity 8 to 10 gallons per minute at a pressure of 200 pounds 

 per square inch; equipped with pressure gauge; adjustable automatic pressure 

 regulator; spacious air chamber to insure constant pressure; complete oiling 

 system; construction such that the parts, especially the valves, are easily 

 accessible and with a complete system of drainage to prevent freezing. 



Power. Gasoline engine of sufficient rating to deliver with ease the power 

 required; preferably four-cycle upright type; and equipped with high-grade 

 carbureter, magneto and dependable oiling system. 



Tank. The capacity of the tank should not be less than 200 gallons and 

 300 is usually perf erable for city work. Provision should be made for washing 

 and draining. 



Housing. For city work, the pump and engine should be housed in order 

 to avoid soiling by the spray. The housing should be so constructed that ^ the 

 sides can be locked down in order to protect the machine from depredations 

 when idle on the streets. 



Agitator. The rotary type of agitator is generally considered best. The 

 construction should be such that it can be disconnected from its motive power, 

 during certain operations.* 



*In using the soluble or miscible oils, it is advisable to disconnect the agitator after the 

 solution is thoroughly mixed, since long continued agitation is likely to impair the emulsion, 

 a spongy mass resulting which resembles freshly churned butter. 



