156 PLANT DISEASES 



with, otherwise the green fodder supply for our towns may 

 suffer to the same extent as the sainfoin crop in some parts 

 of France. 



Eriksson, Kongl. Landthbr.-Akad. Handl. o. Tidskr., 

 1880, No. i. 

 Prillieux, Malad. des Plantes Agric , vol. ii. p. 413, figs. 



ONION SCLEROTINIA 

 (Sclerotinia bulborum, Wakker.) 



Onions, hyacinths, and probably also other bulbs, are 

 often destroyed in immense numbers by this fungus. 

 Yellowish blotches appear on the foliage in spring or early 

 summer. These blotches are soon covered with a velvety 

 olive-brown mould. The mycelium passes down the 

 tissues into the bulb, where blackish sclerotia, varying in 

 size from a rape-seed to a small pea, are formed, more 

 especially in the outermost scales of the bulb, in some 

 instances in such quantities that the surface of the bulb is 

 almost completely covered. During the following spring 

 small, brown, cup-shaped ascophores, supported on a 

 slender, wavy stem, spring from the sclerotia. 



PREVENTIVE MEANS. Spraying with potassium sulphide 

 solution or with dilute Bordeaux mixture on the first 

 symptoms of the disease will check its spread by diffusion 

 of the Botrytis spores. Diseased bulbs should be collected 

 and burned. It is advisable not to plant bulbs where the 

 disease has existed for at least three years, as the sclerotia 

 have been shown to be capable of germination when two 

 years old. 



