124 



N. H. AGR. EXPERIMENT STATION 



[Bulletin 144 



nouneed. In serious cases the bark may be killed over consider- 

 able area and become conspicuously cracked and roughened 

 (Fig. 21). It is set off from the living bark by a very defi- 

 nite 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 throughout the spring, but 

 notes taken the past year indi- 

 cate that it ceases early in June. 

 At first the spots are small, purple 

 areas, but as growth progresses 

 they become yellowish-brown in 

 color and attain a diameter of 

 from i/s to 1/2 inch (Fig. 22). 

 They are quite uniformly cir- 

 cular in outline. The margins are 

 somewhat elevated, giving to the 

 spot a sunken appearance. As 

 the spots become older a sec- 

 ondary growth may spread from 

 the central affected area, pro- 

 ducing a somewhat irregular 

 blotch in which the outline of the 

 original spot can always be recog- 

 nized. (See Fig. 23.) It often 

 happens that several of these 

 areas become confluent, and thus 

 the greater part of the leaf may 

 become affected. Leaves so affected fall from the trees much 

 earlier than under normal conditions, and their working 

 efficiency is always greatly reduced by the middle of the sum- 



Fi(i. 21.— Black Rot Canker. 



