312 Diseases of Greenhouse Crops 



spots surrounded by a definite black border. The 

 spots soon enlarge and when very numerous cause 

 the premature death of the foliage. The trouble 

 is also met with on the blossoms; the petals in this 

 case become spotted and blotched. Affected young 

 blossoms become distorted or fail to open'altogether. 



The Organism. The conidiophores of the fun- 

 gus are short, simple and grayish. The conidia are 

 long, slender, rod shaped, hyaline, and many 

 septate. 



Control. It is claimed by Stone and Smith* that 

 good results were obtained by spraying with Bor- 

 deaux. The latter, however, is objectionable be- 

 cause of its staining the blossoms. Ammoniacal 

 copper carbonate may therefore be used instead. 

 Spraying may be done at intervals of every two 

 weeks. All dead and infected material should be 

 destroyed by fire. 



Root Rot 



Caused by Fusarium viola Wolf. 



This disease causes a rot of the roots and stems. 

 The causal organism (fig, 62, g to i) is usually 

 brought in the house with infected compost. As a 

 control measure soil sterilization is recommended 

 (see pp. 32-43). 



•Stone, G. E., and Smith, R. E, Mass, (Hatch) Agr, Eipt 

 Sta. Ann. Kept. 11: 152, 1892. 



