DISEASES IN GREENHOUSE loi 



Pathogenicity. The pathogenicity or 

 the disease producing power of the sweet 

 pea Rhizoctonia may be readily proven by 

 planting disinfected seeds in sterile soil 

 and also in pots which were inoculated 

 with a pure culture of the fungus (fig. 6) . 

 The best material is a culture which has an 

 abundance of sclerotia. 



The parasite has two stages — the Rhi- 

 zoctonia, and the sclerotial stages. The 

 Rhizoctonia stage consists of long and 

 narrow mycelial branches varying in color 

 from hyaline to reddish brown (fig. ja) . 

 These threads are either imbedded in the 

 substratum in which they grow, or they are 

 aerial, depending on the media on which 

 the fungus is grown. These mycelial 

 threads are the most active and are more 

 concerned in the parasitism of Rhizoc- 

 tonia. The sclerotial stage consists of 



