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the cause and control of fruit tree cankers is extremely sparse, however, 

 and much is outdated. Yet, losses from cankers are increasing year af- 

 ter year and there is no end in sight. 



Several misconceptions about cankers seem widespread among the 

 growers. Many growers describe cankers as "fire blight", but we found 

 no apple trees affected by this disease (which is caused by a bacter- 

 ium) in any part of the state. Others attribute the cankers on their 

 declining trees to viruses. Although this is much more difficult to 

 disprove, this does not seem to be the case either. The most that virus 

 infections can do, aside from their ov7n peculiar symptoms, is to weaken 

 and predispose trees to fungus infections. Cankers, however, are caused 

 by fungi and are generally easily detected and identified. Finally, 

 some growers blame the cankers on winter injury, drought, poor nutrition, 

 and so forth. There is no doubt that these factors may result in tree 

 injury, but it is the fungus infections on these trees that cause the 

 greatest damage, since the progress of the infections continues , long 

 after the occurrence of the condition that helped the fungi become es- 

 tablished. 



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