ORCHARD MANAGEMENT 139 



the trees to be sprayed. A comparatively recent invention, 

 known as the spray-gun, is now rapidly replacing the spray- 

 rod for most types of work. The spray-gun is a short rod 

 equipped with apparatus to regulate the fineness of the spray 

 and the height of the stream. It is light and easy to handle 

 and permits of rapid and thorough work. 



231. Kinds of sprays. Sprays are of two sorts; liquid, 

 and dust sprays, each of which has its advantages. Powder 

 or dust sprays do not require elaborate machinery for their 

 application, and can be used on fruits just before they ripen 

 without injury, and may be applied when the ground is too 

 soft to permit of the use of a heavy liquid spray outfit. On 

 the other hand, liquid sprays can be applied more evenly and 

 at a greater distance than dust sprays, adhere better, and 

 can be used when there is considerable wind. 



Sprays for fungous diseases are known as fungicides. 

 Bordeaux mixture and lime-sulfur preparations are the com- 

 monest. Sprays applied for the purpose of combating insects 

 are called insecticides. These comprise poisons for chewing 

 insects, and contact sprays which kill the insects by corrosive 

 action on the body or by stopping up the breathing pores. 

 Paris green and arsenical poisons are examples of the former; 

 kerosene or crude oil emulsions are examples of the latter. 

 Some materials are used both as insecticides and as fungi- 

 cides, as lime-sulfur solution. There is also the fumigation 

 process in which gas is depended on for destruction of pests. 

 Hydrocyanic acid gas and carbon bisulfide are much em- 

 ployed for this purpose. 



Formulas for making various spray materials are well 

 standardized. The student can obtain from the experiment 

 station in his state definite information in regard to spray 

 formulas, making spray mixtures, and applying sprays for 

 the kinds of insects and diseases common to the section of 

 the country in which he resides. There are also a number 

 of good books on the subject. 



