84 MANUAL OF FRUIT DISEASES 



flesh of the diseased portion becomes light-brown, the surface 

 depressed, and the texture dry and leathery. Within the 

 affected area the fruiting pustules of the pathogene develop 

 in concentric circles; finally they split open, exposing the 

 creamy substance as described for the canker. 



No variety is wholly immune to the disease and some are 

 nearly ruined by it. While it would appear that certain 

 varieties are generally more susceptible than others, the degree 

 of susceptibility varies considerably in different orchards of 

 the same variety, and in different trees of the same variety in 

 any given orchard. The evidence indicates that the kind of 

 soil has little to do with susceptibility. Some hold that the 

 Baldwin, Spitzenberg and Jonathan are most commonly at- 

 tacked, and that the Newtown, Rhode Island and Graven stein 

 are somewhat less susceptible. Those showing less tendency 

 to be affected are the Ben Davis, Northern Spy, Winesap, 

 Tompkins King and Hubbardston. 



Cause of anthracnose. 



The apple-tree anthracnose is caused by the fungus Neofabrcea 

 Malicorticis. In its structure and habits it is very similar to 

 the fungus Pseudopeziza Ribis Kleb., which causes the currant- 

 anthracnose. It spends the winter as almost inactive myce- 

 lium in the cankers. In the spring the fungus renews activities 

 for a short period, but usually stops its further spread as soon 

 as the cambium becomes active. In midsummer those cankers 

 which were initiated the previous fall form acervuli (Fig. 23, 

 extreme left). W T ith the advent of the autumn rains the 

 acervuli become active, the conidia oozing forth in a creamy, 

 gelatinous mass. On being dried by the wind the conidia are 

 carried to other limbs and to fruits. With the return of the 

 rains the conidial masses again ooze out, and the process of 

 dissemination is repeated. In many cases conidia are doubt- 

 less washed by the rain to points below the cankers. In general 

 the conditions prevailing from October to December are very 



