98 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 wilt then be found upon 
careful examination that the tree 
is girdled (Tig. 26) and that finally 
the top dies. Accompanying this 
phenomenon is a profuse develop- 
ment of string-like, hard, black, 
shiny, much-branched strands, #5 to 7: 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 whitergilled, 
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. 
