CERTAIN ELEMENTS IN NURSERY PRACTICE 191 



fall prematurely, thus retarding the development and growth 

 of the plants. Not only does this condition make it necessary 

 for a longer time to elapse before the stock is salable, but 

 premature defoliation also prevents proper maturation of 

 the trees and makes them less able to withstand winter injury, 

 adverse conditions encountered in storage, and the like. 



Methods commonly practiced for the prevention of diseases 

 of older and maturer plants are in many cases not appli- 

 cable to the smaller stock in the nursery, while in many 

 cases certain methods of control can be employed in the 

 nursery which could not be used in the treatment of mature 

 plants. 



One of the important problems confronting the nurseryman 

 is a satisfactory means of applying the various fungicides and 

 insecticides. An apparatus is desirable that will apply the 

 material with the least inconvenience, permitting the work 

 to be performed with considerable rapidity on a wide acreage 

 and as economically as possible. The materials may be ap- 

 plied in a powdered form with air used as a carrier, or as a 

 spray with water as a carrier. 



For spraying nursery stock, there are numerous hand- 

 sprayers that can be used for small plantings, but there is no 

 power machine on the market that is entirely satisfactory for 

 large nursery work. It is difficult to build a machine that can 

 be transported over tall nursery trees. On the other hand, 

 the narrow space separating the nursery rows makes it diffi- 

 cult to construct a sprayer that will run between the rows. 

 With the sprayers that have been used, only a relatively small 

 amount of stock can be covered within a given time ; this not 

 only increases the expense, but in many cases it is impossible 

 to cover all of the susceptible stock before it is too late for 

 the application to be effective. 



Most of these difficulties are overcome when the materials 

 are applied in the powdered form by means of a dusting ma- 



