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 



