APPLE DISEASES 97 
important fruits. In addition to the long lists of plants already 
given, the following may be added as minor hosts: olive, grape, 
crab, maple and potato. It is obvious, then, that a great num- 
ber of widely related plants are likely to be affected by this 
disease. This fact complicates the matter of control, and is a 
factor in the economic importance of the disease. 
It is believed that Armillaria root-rot was observed in America 
as early as 1887 on grape near St. Louis, and later in the states 
of Texas and California. At present the regions most infested 
are those of the Central, Southwest and the Pacific Coast region. 
The disease has attracted particular attention along the Pacific 
Coast during the last fifteen years. 
The damage done by this disease would be difficult to esti- 
mate. But bearing in mind the fact that all of the more com- 
mon fruits are susceptible, and in many localities are severely 
injured, it is not impossible to gain a fair impression of the 
amount of losses incurred. In the state of Arkansas it is stated 
that the losses due to root-rot exceed those of any other disease 
of the apple. In other localities doubtless a similar condition 
exists. As has already been pointed out, the disease in some 
states is more severe on the apple than on other fruits; again, 
the reverse is true. It may not be out of place to cite an exam- 
ple of the possible damage that this root-rot may do. In a 
western prune orchard of about one thousand trees, an average 
of about eighty trees died each year for seven consecutive years 
as a result of Armillaria root-rot. In seven years half the or- 
chard was destroyed. In another case, an orchard of five thou- 
sand trees was reduced at the rate of two hundred and eighty 
trees per year for three consecutive years, the total trees killed 
being eight hundred and fifty. Losses of this kind are always 
keenly felt. 
The disease assumes importance in one or more of the follow- 
ing ways: (1) the roots are killed and hence the trees die in 
one or more seasons; (2) the crown may be injured to such an 
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