GRAPE DISEASES 251 



In the event that half-grown berries are attacked they become 

 irregular in shape. 



The leaves and other parts of the vine when affected by 

 anthracnose show lesions similar to those already de- 

 scribed on the shoots. Spots on the foliage are pale-gray 

 with dark-red borders. Cankers are produced on the petioles 

 and veins. 



Cause of anthracnose. 



The lesions described above are due to the fungus Glceo- 

 sporium ampelophagum ( = Sphaceloma ampelinum). In America 

 only one spore-stage is known; in France, plant pathologists 

 claim to have discovered a winter sexual spore-stage. Ac- 

 cordingly, the name Manginia ampelinum has been substituted. 

 The similarity of the grape-anthracnose fungus to the black- 

 berry and raspberry-anthracnose fungus has resulted in one 

 case, at least, in the suggestion of the possible identity of the 

 two organisms. 



The mycelium of the fungus grows within the affected tissue. 

 Certain threads come to the surface and form fruiting bodies 

 called acervuli. These structures burst through the skin of 

 berries and canes, sending out many erect conidiophores on which 

 conidia are produced. These spores ooze out in a gelatinous 

 mass held together by their sticky coatings. The sticky sub- 

 stance dissolves in water and the spores are thus liberated. 

 They are disseminated by rain and dew, the process occur- 

 ring from the time the berry clusters are yet in the bud 

 until the close of the season. Spores falling on green 

 parts of the vine germinate, and after about a week signs 

 of the anthracnose disease begin to appear. The germ- 

 tubes penetrate the healthy, unbroken epidermis. With 

 the advent of the dormant season the fungus apparently 

 ceases activities. It is not definitely known how the fun- 

 gus passes the winter, but the supposition is that it hi- 

 bernates as mycelium in lesions on the canes and mummied 



