78 Decay in Potato Clamps. [april, 



DECAY IN POTATO CLAMPS DUE 

 TO "BLACK-LEG," 



S. G. Paine and C. M. Haenseler, 



The Department of Plant Physiology and Pathology, 

 Imperial College, London. 



The very large amount of rotting of potatoes in storage 

 which occurred throughout the country, and especially in the 

 Fen district, during the early winter of 191 8, led the Board of 

 Agriculture to investigate the cause of the trouble, and Messrs. 



A. D. Cotton and H. V.Taylor, officers of the Ministry, made a 

 thorough inspection of the clamps in the districts most affected. 

 An account of this inspection, with the first impressions of the 

 investigators as to the causes of the decay, together with a 

 complete discussion of the general question of decay of potatoes 

 in clamps, are contained in an article which appeared in a 

 Supplement (No. 18) entitled " The Cultivation, Composition 

 and Diseases of the Potato," published with the issue of this 

 Journal for March, 1919.* One of us (S. G. P.) was asked to be 

 present during the last inspection, when two farms in the 

 neighbourhood of Spalding, Lincolnshire, were visited. 



The clamps on these farms were not the worst cases that were 

 seen, but their condition was extremely bad ; wreaths of 

 " steam " were rising in the winter air to a height of 4 or 5 ft. 

 above the tops of the clamps, and, after removal of the straw, 

 a thermometer was inserted to a depth of 9 in. amongst the 

 topmost potatoes, and registered a temperature of 60 C. In 

 one instance the top of the clamp had subsided in lengths of 

 10 to 30 ft. as a result of the conversion of the potatoes into a 

 condition of sludge. When the clamps were opened, many of 

 the potatoes at the top were sweet- smelling but soft in texture, 

 and appeared to be par-boiled, but otherwise unaffected. 

 Large quantities, however, were reduced by bacterial action to 

 a stinking pulp. Several specimens of the tubers which were 

 least diseased were collected for bacteriological examination. 

 These were found to contain a very mixed bacterial population, 

 in which saprophytic forms, such as Bacillus mesentericus, 



B. subtilis and B. mycoides predominated. Portions of the pulp 

 were placed upon sterile slices of potato and maintained at 

 different temperatures ; at room temperature there was, 



* Copies of this Supplement may be obtained on application to the 

 Secretary, Ministry of Agriculture and Fisheries, 3, St. James's Square, 

 London, S.W. I, price 6d. net. 



