Aster Diseases 211 



Damping Off 



Caused by Rhizoctonia solani Kuhn. 



Symptoms. The trouble is at first manifested as 

 brownish spots on one side of the seedlings at the 

 surface of the soil. The lesions increase in size until 

 the seedlings are girdled and topple over. In time, 

 the Rhizoctonia fungus spreads over the fallen 

 plants and forms a mat of mycelia over them. 



On older aster plants, a damping off is not pro- 

 duced, but instead the typical Rhizoctonia lesions 

 appear on the stem end and on the roots. For a 

 description of the causal organism and methods of 

 control, see p. 20. 



Root Knot 



Caused by Heterodera radicicola Muhler. 



Symptoms, The disease manifests itself when 

 the plants are about three inches high. The younger 

 portions of the plant produce spindly shoots with 

 dwarfed, disfigured leaves. The color of this growth 

 is yellowish pale to white, the flowers are small and 

 stunted. Such plants are known to florists as "white 

 legs." For a description of the organism and meth- 

 ods of control see Nematode, p. 28. 



Azalea (^Azalea Indica) 



Cultural Considerations, Azaleas are very sensitive 

 as regards water. They require plenty of moisture, 



