INSECTS AFFECTING OHIO SHADE TREES 197 



A power sprayer, such as either of the ones illustrated, is capable 

 of supplying three lines of hose, and with the proper attention, of 

 distributing- 700 to 1000 gallons of mixture per day. 



However, it is not always possible to take a large spraying outfit 

 to the scene of operations, and in such an event a smaller machine is 

 desirable. The outfits illustrated (Plate 19, Figs. 1 and 2) supply 

 such a need very well. 



Aside from the difficulty of application in cities, another obstacle 

 is the matter of the preparation of the sprays. Insect outbreaks are 

 liable to occur in widely separated districts, so that it is impossible to 

 have a central spray-house easily accessible from all points. The 

 difficulty is especially emphasized in the work with the lime-sulfur 

 wash, or in fact, in the preparation of any spray requiring consider- 

 able apparatus. The problem has been largely solved by the city of 

 Cleveland by mounting a steam boiling plant on wheels. 

 Plate 18, Fig. 2. This rig is taken to the scene of operations and 

 stopped near a water plug. A plant of this kind with its four bar- 

 rels for boiling the mixture and heating water is easily capable of 

 furnishing material for one power sprayer. 



The rig was also used to excellent advantage in the preparation 

 of kerosene eimulsion. Plate 18, Fig. 1. The soap and water were 

 placed in a barrel and the steam turned on until the soap was dis- 

 solved. The kerosene was then thrown in and the steam, rushing 

 out, formed a perfect emulsion in an exceedingly short time. Such 

 a rig is capable of furnishing emulsion for three or four power 

 sprayers. 



SPRAYING FORMULAE. 



In the general application of insecticides, the materials divide 

 themselves into two classes according to the manner in which they 

 affect the insect. The first includes the contact sprays which are used 

 against insects possessing mouth parts constructed for piercing the 

 covering tissue and taking out the sap of the plant. Of this class 

 the lime-sulfur wash, kerosene emulsion, etc., are well known illus- 

 trations. The idea in their application is to cover the body of the 

 pest with the spraying mixture. 



The second class of sprays is used against insects that bite 

 out portions of the plant. The active element in them is some 

 poisonous substance such as arsenate of lead, Paris green, etc. 

 They are applied to the surface upon which the insect feeds. 



