MAINE APPLE DISEASES. 361 



thread-like growths project beyond the broken epidermis. 

 Orange-colored spores are formed in these places. It is on the 

 leaves and fruit of the apple that the injuries caused by this rust 

 become of economic importance. Spraying has not been very 

 successful in controlling this disease. Where the rust appears, 

 the removal of red cedars from the neighborhood of apple or- 

 chards is recommended. 



Poivdcry mildciv. The common name for this trouble comes 

 from the appearance of the affected leaves which is shown in 

 Fig. 248. The fungus, Podosphacra o.vyacanthae (DcC.) De- 

 Bary, grows upon both surfaces of the leaf but does not pene- 

 trate the tissues, except to throw in short feeding branches. 

 During the summer many spores are formed and it is the masses 

 of spores which give the white powdery appearance. The par- 

 asite spreads rapidly by means of these summer spores. Later 

 in the season another stage of the fungus develops on the dis- 

 eased leaves and this is indicated by the presence of small but 

 plainly visible, spherical, black bodies which are scattered here 

 and there among the white mycelium. Spores are produced in 

 these bodies which carry the fungus over winter. 



On the apple, the chief damage done by this fungus is in its 

 attacks upon nursery stock where it causes considerable loss. 

 Spraying with diluted lime-sulphur should go far toward con- 

 trolling this disease. 



FRUIT DECAYS. 



During the past 3 years this laboratory has devoted consider- 

 able attention to a study of the fungi which cause decay of ap- 

 ples in Maine. Fungi have been isolated from decaying apples 

 from various places and these have been tested by means of in- 

 oculations in order to determine the extent to which each was 

 capable of causing decay. It has been found that Maine has a 

 considerable number of the apjile decay fungi which have been 

 described from other places but the relative amount of rot caused 

 by some of these fungi under local conditions differs materially 

 from the amount attributed to the same fungi in other parts of 

 the United States. For example the "bitter rot" fungus while 

 it occurs here does very little damage in comparison with the 

 amount of loss resulting from its attacks in other sections. The 

 apple decays which have been found in Maine will be described 



