108 



DISEASES OF ECONOMIC PLANTS 



the buds are unfolding, first using an 8-10-50 mixture; 

 second a 5-7-50 mixture. 

 Leaf spot (Mycosphcerella sentina Desm.) . — • The leaf spot, 

 while rarely completely destruc- 

 tive to foliage or crop, does 

 interfere with the general pro- 

 ductiveness and health of the 

 tree by diminishing its green 

 surface and sometimes by caus- 

 ing defoliation. It is known 

 over a wide range. 



The leaf spot may be distin- 

 guished from the scab and the 

 blight by the fact that the dis- 

 eased area is rather sharply 

 defined and characteristically 

 angular in outline. The center 

 of the spot, usually ashen in 

 color, is surrounded by a narrow 

 brown zone, and this in turn by 

 one of purplish hue. The ashen 

 center bears several very mi- 

 nute dark-colored pycnidia. 



The treatment recommended 

 for pear scab is effective in pre- 

 venting this disease. 

 Leaf blight {Fahroea maculata (Lev.) Atk.). — This leaf 

 blight is almost as widely distributed as is the pear itself, 

 though less abundant in the South and West than in 

 the North and East. Its spot does not exhibit the striking 

 zonal arrangement described for the leaf spot (septoriose), 



Fig. 45. — Pear leaf spot (septo 

 riose). Original. 



