CHAPTER IV 
DIAGNOSING OF DISEASES 
@|UST as the physician finds his greatest difficulty 
in determining the cause of illness, so the tree 
doctor, although knowing the diseases to which 
trees are liable and knowing the remedies, may 
still find trouble in diagnosing the true cause of the evident 
abnormal condition. Here it is that experience and judg- 
ment come in, yet sometimes even an expert remains doubt- 
ful. Nevertheless, by careful examination, in many cases 
even the less experienced can determine what ails the tree. 
Usually, if anything is the matter in any living part of the 
tree, the foliage gives the first indication, and furnishes the 
most readily available symptoms for diagnosis. 
Hence our examination begins with the foliage, to see 
whether it shows any divergence from normal conditions 
in size, quantity, form, or color. With a conception of 
what the normal foliage ought to be, we ascertain whether 
the leaves of the individual under examination are smaller 
than usual, or thinner, whether the foliage as a whole appears 
slim, whether the leaves are wholly or partially discolored, 
whether they are mechanically injured, eaten, crumpled, 
or otherwise misshapen, spotted, wilted, or dead. 
If no local cause, as from fungi or insects, can be ascer- 
tained as surely responsible, we look next for indications 
on twigs, branches and bole as accounting for sickly appear- 
ance of the foliage or death of branchlets. Mechanical 
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