222 The Commercial Apple Industry 



ing in what is known as twig-blight. Confusion very 

 often results from the use of such terms as twig-blight, 

 blossom-blight and trunk-blight. In reality they are syn- 

 onymous, being merely different names to designate the 

 part of the tree infected. 



Fire-blight is more or less prevalent in all apple regions, 

 but has been particularly serious in the Pacific Northwest 

 on account of the presence there of susceptible varieties. 

 The Esopus (Spitzenburg) is more subject to blight than 

 any other leading commercial variety. Spitzenburg or- 

 chards in the Yakima Valley have suffered severely in bad 

 blight years. On the other hand, the heavy Spitzenburg 

 plantings in the Hood River Valley, Oregon, have been 

 very little injured. It is difficult to say just how far 

 local climatic and soil conditions affect the spread of this 

 disease, but unquestionably they are important factors. 



Preventive measures consist in checking wood growth. 

 Blight works on tender succulent wood. Aphids unques- 

 tionably are active in spreading this disease and their con- 

 trol is important. 



After infection, the removal of the diseased portion is 

 the only treatment. In the care of infected branches, the 

 cut should be made about ten inches below the last visible 

 sign of the blight. Wounds should be disinfected with 

 cyanide of mercury, 1 to 500 ; tools should be disinfected 

 with corrosive sublimate, 1 to 1,000. 



Apple rosette. 



The apple rosette is a physiological disease more or less 

 prevalent in certain regions, particularly in the North- 

 west. The disease is evidenced by a shortening of the 

 terminal growth. Buds are crowded together by a failure 



