52 PLANT DISEASES 



it being possible to reach with certainty the exact portions 

 desired. 



On the other hand, a very fine spray does not readily 

 reach the tops of fruit or other trees, consumes more time 

 in application, and much is wasted by wind driving the 

 spray in a wrong direction. 



Again, if the spray is too coarse, it forms drops which 

 either roll off the foliage, or, if they remain, injure the 

 leaves by producing a scorched appearance. 



The various devices for spraying are numerous, ranging 

 from the hand syringe, useful for spraying in houses, to 

 huge steam-power contrivances carrying a tank holding 

 loo gallons or more of solution, and forcing a spray to 

 the top of a large tree. Perhaps the most generally useful 

 form is the barrel pump, intended to be fixed to a good 

 cask mounted on a wheel-barrow. 



I have seen very effective spraying done with a simple 

 bucket-pump costing half-a-crown, the nozzle consisting of 

 two flat, parallel pieces of tin, the outlet being narrowed 

 by hammering until a spray of the required degree of 

 fineness is produced. 



If Bordeaux mixture is used, some arrangement, auto- 

 matic or otherwise, should be present to keep the solution 

 uniformly mixed, otherwise one portion of the spray will 

 be too diluted to effect the desired object, and another 

 portion so concentrated as to injure the foliage. 



Although the first cost is greater, it proves most eco- 

 nomical in the end to have all the pump fittings made of 

 hard brass formed of copper and tin. Soft brass com- 

 posed of copper and zinc should be avoided, as it is 

 corroded by ammonia. 



In spraying plants, it must be remembered that efficacy 



