274 



MANUAL OF FRUIT DISEASES 



the enlargement of the lesion the whole fruit becomes involved, 

 is brownish, shrunken, and eventually shrivels into a dark 

 mummy. The mummy may cling to the tree or it may fall 

 to the ground. While on the tree mummies cling together 

 in groups of two or more. 

 Cause of brown-rot. 



The pathogene, the fungus Sclerotinia cinerea, hibernates in 

 both the fallen and hanging mummies, and in the cankers. From 

 sclerotial crusts in the fallen mummies arise apothecia (Fig. 74) 



in the spring of the 

 year. The hanging 

 mummies furnish a 

 habitation for co- 

 nidia through the 

 winter; in the 

 spring these spores 

 are carried to the 

 susceptible parts. 

 These old clinging 

 mummies as well as 

 the cankers also con- 

 tain mycelium of the fungus, and in the spring conidia are 

 developed from these sources. The source of the primary 

 inoculum is found, then, in both the fallen and hanging 

 mummies, and in the cankers. The inoculum itself consists 

 of both ascospores and conidia, of which the latter are the 

 more important. In fact, it sometimes appears that ascospores 

 are not developed every year, and that they play a very 

 minor role in the life-history of the brown-rot fungus. Spores 

 of either kind are carried to the blossoms, where blossom-blight 

 is induced. The mycelium grows throughout the blossoms, 

 enters the twigs, and finally passes into the large limbs. 

 Conidial tufts develop on the petals, and even on the cankers 

 and blighted twigs, if the atmosphere has a high relative 



FIG. 74. Apothecia of the brown-rot fungus ; 

 attached to fallen mummies. 



