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MANUAL OF FRUIT DISEASES 



extent that the tree may be blown over under the strain of a 

 heavy crop of fruit ; (3) affected trees in bearing usually fail to 

 mature their fruit, particularly in cases of severe infection; 

 or the fruit matures poorly, is stunted and is of an inferior 



quality ; (4) diseased trees often 

 lack the normal amount of -foliage ; 

 (5) affected plants make little or 

 no growth. 



Symptoms of Armillaria root-rot. 

 Evidence of this trouble varies 

 with the part affected and there 

 are no visible signs until consider- 

 able progress has been made by 

 the pathogene. A striking charac- 

 teristic is the marked localization 

 and the slow development of the 

 disease. The average observer 

 will not suspect the presence of 

 root-rot until individuals or groups 

 of trees die among many other ap- 

 parently healthy ones. At some 

 point it will then be found upon 

 careful examination that the tree 

 is girdled (Fig. 26) and that finally 

 the top dies. Accompanying this 

 phenomenon is a profuse develop- 

 ment of string-like, hard, black, 

 shiny, much-branched strands, ^ to ^ of an inch in diameter, 

 in the soil at the base of the tree (Fig. 27). These strands 

 have a peculiar mushroom odor and a tough texture. From 

 these rhizomorphs, as they are called, numerous white-gilled, 

 honey-colored mushrooms may arise in the autumn (Fig. 27). 

 The mushrooms may be found at the base of the affected tree 

 or at some distance along the roots. 



FIG. 26. Armillaria root-rot ; 

 note the girdling of the root. 



