MAINTENANCE 75 



Surface sprinkling is not desirable as it encourages surface rooting 

 and seldom does much good. In case it is necessary to water a shade 

 tree the best plan is to throw up a shallow embankment of earth around 

 the tree just outside the spread of the branches if possible, and flood 

 the enclosed area at intervals not more often than once in five or six 

 days. Many trees and shrubs will be much benefited in time of 

 drought if their tops are sprinkled at sundown on very hot days. 



Spraying. Spraying of plants as a scientific practice is, com- 

 paratively speaking, a modern procedure, but the necessity for doing 

 something to protect plants against insects and plant diseases has been 

 understood since antiquity. In their writings the Greeks, Romans, 

 and Hebrews noted the existence of rusts and mildews, and the plague 

 of locusts is of Biblical record. 



Spraying is only one of several ways of protecting plants and among 

 the others may be enumerated hand picking, fumigating, banding, 

 burning, using fungous diseases as insecticides, crop rotation, soil 

 sterilization and various other more or less practical methods. These 

 other methods are important when understood and put into practice 

 at the right moment and in the right way, but they are inexact com-, 

 pared to spraying and are seldom as efficient. Spraying, by which 

 is meant the use of chemicals to poison or otherwise exterminate 

 animal and vegetable parasites on plants, has been reduced very 

 nearly to an exact science in this country, largely within the last 

 century, and, while it is not the purpose here to go too deeply into this 

 art, some broad rules may be laid down and some little understood 

 points cleared up. 



Our Government and State Experiment Stations have been largely 

 responsible for the rapid strides taken in this art in this country. 

 They have issued many bulletins and spray calendars containing 

 exact directions for combating all the known insect pests and plant 

 diseases and they always stand ready to help any one who asks for it. 

 Yet much of their help comes too late and much money is wasted 

 each year with consequent disappointment, because a few simple 

 principles are not clearly understood. Some of the overlooked factors 

 which are not taken into account are as follows: (i) a spray mixture 

 must be the correct one as, for example, it does no good to use poison 

 upon an insect at a period in its Hfe history when it does not eat; (2) 

 the spray mixture must not injure the plants, or else the cure will be 



