402 AGRICULTURE OF MAINE. 



pathogenicity and interrelation of the various fungi found asso- 

 ciated with leaf spot, fruit decays, and limb cankers in this State. 

 The results of a part of this work have already been. published* 

 and other parts will be published later. It is sufficient for our 

 present purpose to state that out of a large number of fungi iso- 

 lated from leaf spot in Alaine Sphaeropsis malorum was the only 

 one which would produce the disease on inoculation. 



The results obtained here, taken together with the conclu- 

 sions of Scott and Rorer and the work of Lewisf in New 

 Hampshire would seem to indicate that Sphaeropsis is the only 

 one of the fungi occurring so abundantly on the dead spots in 

 apple leaves which is capable of causing the disease in this sec- 

 tion of the country. 



This fungous leaf spot causes a considerable amount of loss 

 in Maine orchards and this loss is not always realized by the ap- 

 ple growers. The dead spots in the leaves interfere with their 

 function, and, in addition to this, large numbers of the diseased 

 leaves fall prematurely, thus seriously interfering with the nutri- 

 tion of the trees. 



As has already been mentioned the fungus causes the canker 

 of the wood and the black rot of the fruit, therefore preventive 

 measures must be directed toward all 3 forms of the disease. 

 Since inoculation experiments indicate that in Maine infection 

 must take place before the middle of July spraying as recom- 

 mended for apple scab would do much to control the disease. 

 This should be supplemented with the removal and destruction 

 of limb cankers and decayed fruit. 



From their observations the writers are convinced that leaves 

 of trees which are well fertilized, cultivated and generally well 

 cared for are not so susceptible to the disease as the leaves of 

 neglected trees. It must be borne in mind, however, that a sim- 

 ilar spotting of the leaves of susceptible varieties may occur as 

 the result of spray injury. 



Rust. This disease of apple leaves and fruit which does great 

 damage in some apple growing districts does not seem, accord- 

 ing to the observations of the writers, to be of very common 



* Lewis, C. E. Apple Diseases Caused by Coryneum foUicolum and 

 Phoma mali. Me. Exp. Sta. Bui. 170, 1909. A New Species of En- 

 domyces from Decaying Apple. Me. Exp. Sta. Bui. 178, 1910. 



tLewis, Isaac M., N. H. Exp. Sta. Rep. 20, pp. 365-369, 1908. 



