CHAPTER VI. 



FUNGOID DISEASES OF MANGELS AND ru:ET. 



I. False Mildew {Pejvnospora schaclitii). 

 Class: PiivcoMVCETE.E ; Order: Peronosporales. 



Both mangels and beet are attacked, the latter 

 to a serious extent in France and Germany. 



Syniptorus. — In May and June the young leaves 

 assume a light green colour, and become crumpled 

 in a bladder-like form with the outside edges 

 turned under. A grey coverino- of mycelium is 

 found on the under side. Plants attacked are 

 dwarfed in growth, or may be altogether destroyed. 

 Single plants or patches suffer. 



Cause. — The greyish patches on the under side 

 of the leaf consist of conidiophores of the fungus 

 Peronospora schaclitii which causes the disease. 

 The conidiophores grow through the stomata and 

 bear at the tips oval-shaped spores that are easily 

 detached and carried by the wind. They 

 germinate readily on a moist surface, and if ger- 

 mination takes place on beet or mangel leaves the 

 germ tube enters and grows within. Resting spores, 



with thick walls, are formed within the dead leaves, 



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