72 



MANUAL OF FRUIT DISEASES 



WHITE HEART-ROT 

 Caused by Fomes igniarius (Fries) Gillet 



This disease is far more important in the forest than in the 

 orchard. Among some of the trees attacked, besides the 

 apple, are beech, aspen, balm-of-Gilead, willow, sugar maple, 

 red maple, striped maple, silver maple, yellow birch, butter- 

 nut, black walnut, 

 oak and hickory. 

 Most destruction 

 is wrought in the 

 beech and aspen. 

 But as an apple- 

 tree heart disease, 

 white heart-rot is 

 perhaps the most 

 prevalent and the 

 most destructive 

 trouble of this type. 

 Although this 



c\ mc^fl sf* ri*}^ iM^f^Ti 

 FIG. 20. Fruiting body of the white heart-rot 



pathogene. known tor about 



two hundred years, 



it was not thoroughly studied until 1878. Little has been 

 learned since that time, in spite of the fact that the disease is 

 world wide in its range. It has been found in practically every 

 country of the globe as well as in all the more important islands. 

 The causal pathogene does not appear to be limited in its geo- 

 graphical range by climatic conditions, being found not only in 

 temperate zones, but in the frigid and tropical regions as well. 



Symptoms. 



The characters by which white heart-rot may be recognized 

 are of two general types, external and internal. The first 



