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STUDIES IN BACTERIOSIS IP. 



A BROWN BLOTCH DISEASE OF CULTIVATED 

 MUSHROOMS. 



By SYDNEY G. PAINE. 



{Lecturer in Plant BacterioJogy in the Depart rnenl of Plant Physiology and 

 Pathology of the Imperial College of Science and Technology, London.) 



INTRODUCTIOX. 



During the spring of 1918 a disease of mushrooms was observed in the 

 beds of a large nursery in Brentford, Middlesex. Mushrooms have been 

 cultivated there for upwards of forty years, and although the disease 

 was not entirely new to the grower there would seem to have been no 

 outbreak in the past of comparable severity. Previous occurrences had 

 been of little importance and had been attributed to the effect of draughts. 

 The disease was first noticed in April, and threatened to assume serious 

 proportions. On examination of one of the houses in the first week of 

 May about one-third of the crop in certain parts of the house was found 

 to be affected^. The financial loss at this time when the wholesale price 

 of mushrooms was at its maximum must have been considerable, affected 

 mushrooms being so disfigured as to be unsaleable. Later on in the 

 month, however, the disease became less prevalent, and towards the end 

 of June had become insignificant in amount. The reason for this rapid 

 falling off will be discussed later. 



The Symptoms of the Disease. 



Circular or irregular spots of a chestnut brown colour appear on the 

 surface of the cap of the mushroom when this has attained a diameter 

 of an inch or so; they spread rapidly and coalesce to form large patches 

 which occasionally cover the entire surface of the pileus. (See Fig. 1.) 

 The stalks also may show the disease, but it is characteristically a disease 



1 The first of this sorios of studies appears in Tin: Jnunial of Ai/riciilliinil Science, 

 vol. VIII, 1917. 



- The areas most aflfected were tiiose within ten feet of either (h)or: tiiis seemed to 

 indicate that draughts were in some way eonneeted with the spread of the disease. 



