472 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



Hosts 



From numerous parts of Europe and 

 America it is reported that many forest 

 trees, including various evergreens, the 

 birch, beech, walnut and oak, as well as 

 such fruit trees as the apple, plum, 

 cherry, peach, citrus and olive, besides 

 certain bush fruits and the grape, are 

 attacked by very similar, if not identical, 

 mushroom root rots. Along our Pacific 

 coast, mushroom root rot is prevalent on 

 many kinds of trees and shrubs. In 

 Western Washington, Lawrence reports 

 its presence among several native trees, 

 both evergreen and deciduous, and men- 

 tions that in orchard and field the apple, 

 plum, cherry, gooseberry, currant, black- 

 berry, raspberry and loganberry were 

 found to be badly Injured or killed. In 

 California, Home has reported that it 

 occurs throughout the state, attacking a 

 great variety of hosts. He says that it 

 appears to be capable of attacking almost 

 any plant, in fact, that it is somewhat 

 woody and long-lived. 



Symptoms 



The symptoms of the disease vary 

 somewhat, depending upon the point at 

 which the tree is attacked, the rapidity 

 or slowness with which the parasitic 

 fungus spreads, and other conditions. It 

 is generally not until the trouble has 

 made considerable progress that the fii'st 

 external evidence of the attack appears 

 in its effect on the health of the tree. The 

 earliest indication is usually a retarded 

 growth, attended by early dropping of the 

 leaves. The foliage generally presents an 

 unnatural appearance. Often this is con- 

 fined to that side of the tree correspond- 

 ing with the side of the trunk first at- 

 tacked. The fruit is usually poor and 

 stunted. A tree may sometimes show 

 such symptoms for two or three years be- 

 fore it finally succumbs, but death fre- 

 quently occurs during the season in 

 which the symptoms first appear, or dur- 

 ing the following year. In rapid attacks, 

 the leaves often become yellow early in 

 the summer. Not infrequently the entire 

 foliage suddenly withers and the whole 

 tree dies in midseason. Again, death may 



occur during the winter, in which case 

 the tree fails to leaf out in the spring. 

 Sometimes, but not always, clusters of 

 mushrooms of a light brownish color 

 come up in the autumn around the base 

 of the trunk, or push through the soil 

 above diseased roots. In some cases, this 

 occurs before the tree is totally dead. 



As soon as a tree shows the first signs 

 of trouble, it should be examined by 

 digging the soil away from the base, and 

 a search should be made for decayed areas 

 on the trunk and roots (Fig. 2). and for 



Fij;. :;. Trunk of Apple Tree Which Dieil in 

 Midsummer. Dead bai-k removed to sliow 

 layers of wliite fungus under bark. 



peculiar black, rootletlike branching 

 strands, mostly about the thickness of the 

 lead in a pencil, clinging to the bark. 

 These strands, known as rhizomorphs, are 

 characteristic of the disease, since they 

 are a special form of the fungus which 

 causes the rot. They can be distinguished 

 from the roots of any small plants which 

 may also be present in the soil, by their 

 peculiar irregular method of branching 

 and by the white interior substance which 

 can be rather easily separated from the 



