125 



"BLACK NECK" OR WILT DISEASE OF ASTERS. 



By WILFRID ROBINSON, M.Sc. 



Lecturer in Economic Botany, Manchester University. 



(With Plates XXV, XXVI.) 



The wilt disease of China Asters is extremely prevalent in market 

 gardens around Manchester, being locally known as "Black Neck" or 

 "Black Leg" disease, and in recent years it has attacked and destroyed 

 large quantities of asters in the district. My attention was drawn to 

 the disease by a large grower of asters at Northenden late in the season 

 of 1913, but the plants then examined were so badly affected that it 

 was impossible to determine accurately the causal organism. Several 

 fungi were isolated from the dead plants but owing to lack of suitable 

 material for inoculation experiments the investigation did not at that 

 time proceed further. Early in 1914, however, the same grower notified 

 me that his seedling asters were seriously diseased, and in the course 

 of a very short time some thousands were destroyed. The seedlings 

 thus attacked formed the starting point for the study of the disease 

 which was under observation in this garden throughout the season. 



It soon became clear that the aster may show the characteristic 

 symptoms of the disease at any period in its growth. While many 

 seedlings succumb completely without growing further, the infected 

 plants often continue their growth and may even reach the flowering 

 stage before they collapse. The leaves of such older plants show clear 

 signs of flagging from below upwards, while seedlings exhibiting the 

 same symptoms often droop and damp off. The lower part of the 

 stem shows a very distinct browning or blackening of the tissues for 

 a short distance above the ground level and in many cases the whole 

 of the cortical tissues are decaying. These decaying tissues form an 

 extremely suitable medium for the growth of the various saprophytic 

 fungi, which are usually found in abundance in the latest stages of the 



