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THE FAU.MERS HANDBOOK. 



If the straws of such plants are examined at the base or butt they will be 

 found to be discoloured and usually blackened from the ground level upwards, 

 for as much as two inches in bad rasps. The roots, especially in later stages of 

 the disease, show an abnormal development of root hairs, giving them a 

 "fuzzy" and woolly appearance. The roo's become brittle and break off readily 

 if the plants are pulled up. Sometimes an excessive development of secondary 

 roots is noticed. The butts of the plants at the ground levels are, in late 

 stages, usually rotted through, which gives rise to the signs of mal-nutrition 

 in the ears referred to above. When examined microscopically, a felt-like 



Fig. 15. — Take-all on wheat. 



Bases of young wheat plants killed by Take-all fungus (Ophiobolns graminis). 

 Note the characteristic blackened areas on the lower parts of the stems (" Black feet "). 



mycelium (fungus threads) or plate of a black to brown colour is noticed 

 encrusting the stems and leaf sheaths of the plants at the base. These fungus 

 threads are ramifying in the basal leaf sheaths and in the straw, and result 

 in the early death of many of the cells. In very advanced stages there may 

 be noticed on the blackened straw of the dead plants a development of the 

 fungus spore cases. These shed their spores into the soil. 



Infection takes place from the soil, the young and growing wheat plant 

 being attacked by the fungus, whose threads fasten upon it near the ground 

 level and in the root-system and grow on its tissues. 



Various grasses are also affected with and can convey the disease, e.g., 

 Brome grass (JJromus sterilis), barley grass (Hordeum murinum), and 

 Agropyum sp. The occurrence on oats is rare in Australia, though not 

 entirely unknown. Barley is attacked. 



Controls. — Stubble from a diseased crop should be burnt off. This is not 

 a completely satisfactory method of control, as the spores in the soil and on 

 the base of the plant are seldom destroyed. Starve out the fungus in the 

 soil by rotation and bare fallow. Oats and bare fallow can be employed in 

 the rotation system. Oats are very rarely affected, but barley should be 

 avoided. Barley should not immediately follow wheat nor should wheat 



