18 



N. H. AGR. EXPERIMENT STATION. 



[Bulletin 157 



are often much more pronounced. In serious cases the bark maj' 

 be killed over considerable area and become conspicuously- 

 cracked and roughened (Fig. 21). It is set off from the living 

 bark by a very definite boundary. Limbs are often so nearly 



girdled that the parts beyond die. 

 Pycnida similar to those on the 

 fruit are found on the canker. 



Like the other diseases attrib- 

 uted to Sphoeropsis Malorum, the 

 leaf spot is of general occurrence 

 in New Hampshire. The disease 

 makes its appearance on the 

 leaves shortly after they unfold 

 from the bud. Infection con- 

 tinues thruout the spring, but 

 notes taken the past two years 

 indicate that it is uncommon after 

 the middle of June. At first the 

 spots are small, jDurple areas, but 

 as growth progresses they become 

 yellowish-brown in color and 

 attain a diameter of from 1-8 to 

 1-2 inch (Fig. 22). They are 

 quite uniformly circular in out- 

 line. The margins are somewhat 

 elevated, giving to the spot a 

 sunken appearance. As the spots 

 become older a secondary growth 

 may spread from the central 

 affected area, producing a some- 

 what irregular blotch in which 

 the outline of the original spot 

 can always be recognized. (See 

 Fig. 23.) It often happens that 

 several of these areas become con- 

 fluent, and thus the greater part 

 of the leaf may become affected. Spotted leaves fall from the 

 trees early in the fall and their working efficiency is always 

 greatly reduced by the middle of the summer. (See Figs. 24 



Fig. 21.— Black Rot Canker. 



