82 FUNGOID DISEASES 



Preventive Measures. — 



T. Spray early with Bordeaux Mixture (p. 25). 



2. Keep the plants in good growing condition by 

 suitable manurial dressings- 



III. Black Leg or Stem Rot [Bacilhtspkyto- 

 pktkorus^). — Sometimes whole areas (75 per cent of 

 the crop) become completely rotten, the late applica- 

 tion of farmyard manure and moist warm weather 

 favouring the spread of the attack. Cereals have 

 been proved to be immune. 



Sympt07ns. — Seen in June and July, attacked 

 plants becoming wilted and discoloured from below 

 upwards, the leaves and the stems below and above 

 ground being affected. Usually spreads quickly 

 from one plant to another, and the sets may be- 

 come rotten. The chief lesions occur in the vicinity 

 of the ground level, in the form of blackened canker- 

 like areas, hence the name '' black leg ". 



Cause. — Though various fungi are found in the 

 tissues, the primary cause of the disease is a small 

 parasitic organism, Bacillus pkytopkthor7ts, which 

 destroys the living tissues of the plant ; it is un- 

 doubtedly assisted in the later stages by such fungi 

 as Botrytis cinerea, Mucor and Fttsaritcni species, 

 and others. 



^This does not belong to the true fungi. A disease is de- 

 scribed by Harrison, the symptoms of which resemble the above, under 

 the name of Bacillus solauisaprus (Cent. Blatt f Bact., Bd. 17, 

 No. 1-2). 



