20 Diseases of Greenhouse Crops 



Root Rot 

 Caused by Rhizoctonia solani Kuhn. 



Although not so virulent as Pythium, Rhizoctonia 

 is a frequent cause of considerable failure in green- 

 house culture. The fungus causes a damping off of 

 seedlings and cuttings and a serious root rot. 



Symptoms, The symptoms of Rhizoctonia rot or ^ 

 wilt do not differ materially from those produced by 

 Fythium de Baryanum. On older plants, however, 

 Rhizoctonia produces cankers or deep lesions which 

 are very characteristic. These are formed on the 

 roots as well as on the base of the stem. The lesions 

 are reddish brown and extend into the cortical or 

 vital layer as well as into the woody tissue. There 

 is perhaps no other parasitic fungus which is so 

 widespread and which is capable of attacking such 

 a variety of hosts as Rhizoctonia. The work of 

 Peltier * shows that the following greenhouse crops 

 are susceptible to Rhizoctonia: beet, bean, cauli- 

 flower, celery, cucumber, egg plant, horseradish, 

 lettuce, muskmelon, pepper, radish, tomato, sweet 

 alyssum, amaranthus, ornamental asparagus, china 

 aster, begonia, candytuft, carnation, coleus, dianthus, 

 lavatera, lobelia, pansy, poinsettia, sweet pea, violet. 



Cuttings of the following hosts are also reported 

 by Peltier to damp off from Rhizoctonia : Abutilon 

 hybridum, var. lavitzii, Acalypha wilkesiana, var. 



•Peltier, G. L., Illinois Agr. Expt. Sta., Bui. 189: 283-391, 1916. 



