40 Disease and Death of Trees — Generalities 



The "black" fungi, which attack the bark, find entrance 

 through small wounds made by hailstones, insects, or break- 

 ages. Working between bark and wood in the bast or 

 bark portions of the cambium and into the wood, tliey 

 destroy living tissue, and, if the injury is e\tensi\-e in younger 

 trees and twigs, they become dried out and killed. 



These bark-fungi are found especiall}- on conifers, pine, 

 spruce, fir, etc. Their presence is usually not discovered 

 until a number of pin-sized, white, black, bright red, or 

 yellowish pustules or spots — the fruit-bodies of the fungus 

 — a])pear on the outside of the dead bark. 



In deciduous-leaved trees the same class of fungi produce 

 maKormations known as canker. On small areas of irreg- 

 ular shape the bark is killed, and in the attempt to heal the 

 damage by callusing each season, and at the same time in 

 the continuance from year to year of the fungus growth, all 

 kinds of curious shapes of the wound are produced. Small 

 fruit-bodies, white with minute red spots, appearing on the 

 dead bark of the margin of the wound are the indications 

 of the fungus causing these malformations. 



Similar to this disease is the hlack-knot of the plum and 

 cherry trees, a fungus producing swellings of irregular 

 shape. 



By reducing the water-supply, especially in dry years, 

 these bark-infesting fungi cause sometimes the partial or 

 entire death of twigs and branches. 



Various fungi working on }oung trees and on foliage give 

 rise to swellings of the leaves like boils, and to the curious 

 deformations known as "witch's broom." Timely removal 

 of these arrests the progress of the disease. 



The condition and age of the tree determine, to a large 

 extent, how far these fungus attacks may be detrimental. 



The rot fungi, which produce the decay of wood, are the 



