38 



It would seem that the disease here is remarkably virulent. At 

 least, the writer has been able to find no records of such wholesale 

 destruction as it has caused in these inland districts. Unless the viru- 

 lence of the disease should become lessened in the course of a few years, 

 a phenomenon that would not be without parallel, the future of pear 

 growing in these inland areas is not clear. 



Some varieties, like Flemish Beauty, are notably more resistant than 

 others, and a bright ray of hope exists in the possibilit}^ of transfer- 

 ring this resisting power to other varieties. This, however, will require 

 many years of experimenting. 



The Idaho pear is particularly susceptible to blight, and should not 

 be planted in infested districts on that account. 



CROWN GALL OR ROOT GALL. 



This disease causes galls to appear on the roots of various trees and 

 shrubs. On fruit trees it commonl}' forms spherical swellings of 

 various sizes, occasional!}^ as large as a walnut. These globular bodies 

 have usuall}^ a peculiar warty surface. They should not be confused 

 with the galls formed by woolly aphis, which, moreover, are smaller 

 and usually oval or irregular. Besides in aphis galls some of the 

 ""wool" is usuall}^ to be foimd. 



It frequently happens that when the roots are affected with this 

 disease the secondary roots are abnormally abundant and often some- 

 what spongy in texture. 



Particular attention is called to this disease because a good many 

 nurser}^ trees have been sold in the Northwest with the roots affected 

 by it. A safer rule is to reject all trees diseased with the galls, even 

 if the latter have been removed. We have found that they are sure to 

 appear again. 



No remedy is known, and, as the disease appears to be contagious, 

 every effo>rt should be made to prevent the sale of nursery stock affected 

 by it. 



Prof. J. W. Toume}" has recent]}^ discovered in Arizona that the 

 crown gall of the almond is caused bj- a slime mold which he names 

 Dendrophagus glohos us. 



I have been unable to discover this or any similar organism in the 

 galls on apple roots. 



