270 "Wilt" or "Crown-Rot" Disease of Carnations 



I should not at this stage like to predict, and the question can only 

 be solved by a comparative study of the two fungi. 



This disease exists throughout the Union of South Africa, but is 

 particularly bad in the Province of Natal where carnations are being 

 largely cultivated for market purposes. 



The investigation was undertaken primarily to test the growth of 

 the fungus in pure culture in the presence of various chemicals ; thus 

 it was hoped that some light would be thrown on practical methods 

 of control. Field experiments thus far conducted are not very conclusive 

 and further investigations will have to be carried out in the field. 



It is my pleasant duty to express my indebtedness to Mr B. A. Bell, 

 Krantzkloof, Natal. Not only did he place his plots at our disposal 

 for experimental purposes, but at a time when I could with difficulty 

 leave the laboratory he kept a full record of how the experiments were 

 going and in time submitted a very complete report. 



To Mr I. B. Pole Evans, under whose direction the work was under- 

 taken, I am grateful for many helpful suggestions and advice. 



The numbers and the word "Plate" bracketed after the colours 

 refer to the colour chart Repertoire de Couleurs published by the Societe 

 Francaise des Chrysanthemistes. 



A. The Disease. 



I. Symptoms of Disease. 



The lower leaves of the plants die and the sides turn upwards, 

 the colour changes to a sickly white and the leaves are more upright 

 than are those of healthy plants. The upper leaves have a withered 

 and shrivelled appearance, and soon the affected plant is dead. The 

 bast of the stem in the affected area is most frequently soft and easily 

 separated from the wood. Badly diseased plants, when pulled, usually 

 break off in this region slightly below the soil. The xylem or wood 

 just above this rotten area is brownish in colour and permeated by the 

 threads of the causal fungus. 



II. Cause of the Disease. 



1. Isolation of the causal fungus. In January, 1911, a number 

 of carnations in Large tins suddenly started wilting with the symptoms 

 given above. Small pieces of diseased tissue were sterilised in mercuric 

 chloride ( 1 : L000) and, alter being washed in distilled water, were shaken 

 up in sterilised melted beef-broth agar and poured into plates, which 



