300 Diseases of Greenhouse Crops 



in France. It is doubtful if it is yet to be feared 

 in the United States. 



Control. Care and vigilance should be exercised 

 to prevent the introduction of the disease to the 

 United States. All infected material should be de- 

 stroyed by fire and the plants should be sprayed with 

 a standard fungicide. 



American Anthracnose 



Caused by Glomerella cincta (B. and C.) S. 

 and S. 



The American anthracnose is very prevalent on 

 hothouse orchids. The variety most susceptible to 

 the disease is Sobralia macramtha. The trouble is 

 first noticed by a discoloration on the stems which 

 soon become brown almost to black while the tender 

 interior tissue becomes soft and decayed. Later 

 the spore pustules appear in great abundance on 

 the dead parts. On the leaves the disease works 

 in a way similar to that found on the stems. The 

 trouble, however, nearly always starts from the tip 

 and works downwards (fig. 59, c). There is usu- 

 ally a distinct line of demarkation between the 

 healthy and the diseased tissue. 



The Organism. The conidial or summer stage 

 of the fungus was described by Halsted.* The 

 conidia are elliptic and guttulate. Setffi may often 

 be present, but they are generally obscured by the 



* Halsted, B. D., New Jersey Agr. Ezpt. Sta., Fourteenth Ann. 

 Kept.: 414-41S. i893. 



