ANNUAL REPORTS. 269 



and in any case it is rendered unsightly and its market value 

 decreased. Aside from the direct injury produced 

 by the disease, the breaking of the skin of the fruit 

 opens the way for the soft rot fungi, which soon des- 

 troy it. The spots on the leaves and fruit are the 

 source of an abundant crop of spores, which are able 

 to start the disease at once in new places. The fungus 

 lives through the winter in the fallen leaves producing 

 another form of spore in the spring. These spores are car- 

 ried by the wind to the young leaves and start the disease 

 anew. Sprayed apples have not suffered from this disease. 

 Black Rot (Sphaeropsis malorum Berk.). But very few 

 orchards have been visited in which this disease does not 

 occur. On the leaves it produces brown, dead spots of 

 irregular shape. It attacks the fruit when in its ripening 

 stages or when in storage. Affected apples decay rapidly, 

 turning a reddish brown at first but later becoming black. 

 They gradually dry out becoming much wrinkled and 

 shrunken. On the surface of the rotting apple may be 

 seen numerous small dots called pycnidia. A section 

 through one of these shows it to be filled with egg-shaped 

 spores. These spores escape through an opening at the 

 apex of the pycnidium to start the disease anew. The 

 fungus is also the cause of cankers on the limbs. The major- 

 ity of the cankered limbs in the orchards of the state have 

 this origin. The disease is found on the larger limbs more 

 often than on the smaller, sometimes completely girdling 

 them, thus causing the death of all parts beyond. The 

 bark of the cankered spot becomes much roughened and 

 the line between the dead and living tissue is often sharply 

 marked, making the canker quite conspicuous. A fruiting 

 stage similar to that on the apples is produced on the 

 cankered limb. (See plate 15.) 



Illinois Apple Tree Canker (Nummularia discreta, Tul.). 

 This canker is often found on the large limbs and even on 

 the trunks of trees. In fruiting the fungus produces con- 

 spicuous circular spots on the bark from an eighth to a 



