CHAPTEK III 



DISEASES AND PESTS 



A. Constitutional Weakness and Diseases. — Under 

 this head are understood all ailments which are 

 not caused by living enemies. The most universal 

 of these are the various effects of malnutrition, but 

 the most certainly fatal, directly or indirectly, is old 

 age. Sure as old age is ultimately to overcome 

 every tree which escapes all other ills, the time of its 

 coming, and the loss it entails, are by no means beyond 

 control. Trees unfavourably located or badly treated, 

 suffer the same decrease in thickness of trunk, in size 

 and number of leaves, and in productiveness, finally 

 reaching sterility, which mark the coming death of 

 very old trees. Trees of less than middle age do not 

 usually follow the course of very old trees to the extent 

 of dying, but linger until their weakened condition 

 makes them succumb to some more sudden death. 

 Such trees are as useless before they die as afterward. 

 When trees show symptoms of premature old age it 

 is the planter's business to ascertain and remedy the 

 cause as best he can. Unless the cause is climatic, 

 and sometimes when it is so, the remedy will be clear 

 if the cause can be found. The real cause may turn 

 out to be a living enemy, or it may be too little or 

 too much moisture, or faulty nutrition, or mechanical 

 injury. When no cause can be found, the trees should 

 be destroyed, to get rid of possible points of attack by, 

 and centres for the spread of, living enemies. Very 



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