104 FUNGOID DISEASES 



and the mycelium remains over the winter in the 

 roots. 



Precautions. — 



1. Remove all diseased plants. 



2. Grow some other crop for a year or two. 



3. Keep down weeds. 



II. Leaf Spot {Cercospora beticola). Fungi 

 Imperfecti ; Order : Moniliales. 



Both mano^els and sug^ar beet are attacked. 



Symptoms. — Very small grey round spots, with 

 a dark red circumference, appear on the leaf in 

 summer, consisting of conidiophores bearing long, 

 tail-like, colourless conidia with cross walls. With a 

 few spots only, no serious damage results ; if an 

 abundance the plant suffers. 



Cause. — The fungus Cercosp07'a beticola causes 

 the disease. The long septate conidia are carried 

 by the wind on to healthy leaves, where they 

 germinate. Growth is limited in area, each spot 

 being the result of a separate infection. Winter 

 spores are not known. 



The damage caused is not as a rule serious, and 

 no satisfactory preventive can be given ; burn the 

 leaves after harvesting, if the disease is abundant. 



III. Leaf Brown {Sporidesmium putr'efaciens, 

 Fuckel). Fungi Imperfecti ; Order : Moniliales. 



Both mangels and sug^ar beet suffer. 

 Sympto77is. — Appears in late summer and 

 autumn ; the oldest leaves are attacked, the 



