60 Lessons in Fruit Growing. 



maturity and may continue to develop during storage 

 (Fig. 18). It appears as a small, circular spot of pale-brown- 

 ish tissue, slightly sunken, which increases by concentric 



Fia. 18. Apple affected with bitter rot. (After Alwood.) 



areas. The affected part, which usually has a bitter taste, 

 becomes softened as the decay extends into the tissues. 



Preventive measures. Spraying as the fruit approaches 

 maturity, with ammoniacal solution of copper carbonate, 

 or a solution of potassium sulfide,' tends to prevent this 

 disease. Varieties specially subject to it should be dis- 

 carded. 



65. The apple canker, which is caused by the fungus 

 Sphceropsis malorum^ is common and often very destruct- 

 ive in orchards in the older apple-growing regions of the 

 United States. In badly infested trees, the disease is indi- 

 cated by dark and enlarged sections of the larger limbs, on 

 which the bark is thickened and much roughened. These 

 diseased sections are often six or more feet long. A por- 



'For formulae for these spraying compounds, see " Principles of Plant Cul- 

 ture." 



