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FUNGOUS DISEASES OF PLANTS 



XXI. SPONGY DRY ROT FUNGUS OF APPLE 



Volutella fructi Stevens & Hall 



Stevens, F. L., and Hall, J. G. The Volutella Rot. N. C. Agl. Exp. Sta. 

 Built. 196: 41-48. 1907. 



The rot of apples produced by this fungus has been reported 

 from North Carolina in particular, although the disease has also 

 been found upon apples from other states. The disease usually 

 begins as a small spot which gradually increases to include the 

 whole fruit. A characteristic of the injury 

 is found in the coal black color of the older 

 portions of the spot. 



The effect upon the tissues is to produce a 

 rather spongy dryness, and the whole affected 

 tissue is penetrated by a much-branched, 

 closely septate mycelium, most abundant, 

 however, close to the cuticle ; in fact, a sub- 

 cuticular, hyaline stroma is formed, which 

 in places eventually becomes palisade in 

 arrangement. From these stromatic forma- 

 tions arise a mass of erect tuberculate hyphas 

 bearing numerous spores. Setae are present, 

 originating in the midst of the sporogenous 

 hyphae, each seta produced from the tip of a 

 single hypha. These vary from 100 to 400 /* 

 in length, and may be from 5 to 8 /m in 

 diameter near the base. The conidiophores arise much higher up, 

 and they are relatively short, simple, fertile hyphas, each abscising 

 many oblong-fusoid to falcate-fusoidal spores (Fig. 149). 



This fungus grows readily in culture upon ordinary nutrient 

 media, and the color of the mycelium varies greatly, being almost 

 hyaline on some and practically black on other media. Upon the 

 host the sporodochia occur in concentric circles, and these are 

 commonly subcuticular at first, becoming erumpent. The conidia 

 are continuous, hyaline to olivaceous, and about the length of the 

 normal conidiophores. The fungus has only been found on the 

 apple, to which it is probably confined. The disease is easily dis- 

 tinguished from the fruit spot. 



Fig. 149. Volutella 

 fructi. (After Stevens) 



