302 Diseases of Greenhouse Crops 



and to prevent them from finding a place in the 

 manure or compost pile. 



European Anthracnose 



Caused by GlcBosporium affine Sacc. 



This disease has been reported by Sorauer* as 

 very serious on cultivated orchids. The trouble is 

 prevalent in overheated hothouses and on plants 

 which have been excessively fertilized. 



Symptoms. On the leaves, anthracnose causes a 

 discoloration and a drying which starts at the tip, 

 or at the periphery or border. Usually the young- 

 est foliage is attacked first. In severe cases, the 

 older leaves and even the bulbs become diseased, 

 wither, and dry up. The disease is carried about 

 with infected bulbs. The same trouble also attacks 

 other orchids such as Cattleya Mendelii and Cypri- 

 pedium laevegatum. 



The Organism. In structure, GloBOsporium affine 

 differs very little from other Gleosporiums. The 

 fungus attacks the epidermis, then works into the 

 mesophyllic layer of cells, where the chloroplasts are 

 destroyed. This explains the disappearance of the 

 green coloring matter in the affected parts. The 

 spore pustules are formed under the epidermis, the 

 latter bursting as the spores accumulate. The spores 

 are formed on what appears to be a pseudostroma. 

 The spores are one-celled, hyaline, cylindrical, and 



•Sorauer, V. P., Zeitsch. PflaDzenkr. 21:387-395, 1911. 



