SYMPTOMS OF DISEASE. 19 



leaf or needle. Often the fruiting bodies develop only 

 on the underside of the needles or leaves. 



Premature dying of the foliage of tops, limbs, 

 branches, or twigs may be an indication of local inter- 

 ference with the water supply, the result of partial or 

 complete girdling by porcupines and other mammals 

 (deer, cattle, sheep) or by insects. Leaf or twig inhab- 

 iting fungi may, however, locally attack the foliage. 

 Lightning sometimes kills limbs. On old yellow pines, 

 for instance, it is often possible to follow the track a 

 discharge of lightning has taken down the tree by the 

 limbs it has killed on its way. Dead limbs may also be 

 an outward sign of some local trouble in the root 

 system. 



Partial or total dying (reddening, yellowing, pre- 

 mature dropping) of the foliage of single trees may be 

 caused by a variety of agencies, but can, except in the 

 case of needle miners and certain needle fungi, almost 

 invariably be traced to some interference with the water 

 supply. If the tree dies in a comparatively short time, 

 the probabilities are that the trouble is located at the 

 butt or in the root system. It is frequently, but not 

 always, a sign of attack by bark beetles. 



When the foliage of practically all the trees in a 

 stand is affected at the same time it indicates that 

 the leaves or needles may have been poisoned by smelter 

 fumes or similar gaseous products or killed by fire. It 

 may also mean invasion by insects or that the water 

 supply is in some way out of order (winter injury, 

 p. 16). 



