332 THE farmers' handbook. 



FUNGUS DISEASES OF WHEAT.* 



Among the common troubles that the wheat-grower has to fight are 



Stinking Smut or Bunt, Take-all, Flag Smut, and Rust. All are due to 

 fungi, and from time to time are responsible for considerable Losses. Rust, 



fortunately, is somewhat intermittent in its attacks — several years some- 

 times elapsing between serious outbreaks in the grain districts; bvit Bunt 

 is ever present, and the farmer's only means of controlling is by treating his 

 seed wheat with a fungicide before sowing. Efforts have been made to 

 produce varieties resistant to these fungi, and some success has been 

 achieved in relation to Rust, mainly by the production of wheats that grow 

 so quickly that they mature before that parasitic enemy; but with Bunt the 

 case has been different, those that have proved resistant are not generally 

 prolific enough for cultivation on an extensive scale. 



Bunt or Stinking Smut {Tilletia iritici (Bjerk) Wint. ; T. levis, Kuehn.). 



Two pests are usually known as Smut — Bunt or Stinking Smut, and 

 Loose or Flying Smut. When, however, the farmer talks about " smut," 

 he almost without exception refers to Stinking Bunt or Stinking Smut, 

 which is caused by one or other of two closely-related fungi whose scientific 

 names are given above. Stinking Smut is so called from the objection- 

 able smell which is quite noticeable even if only a little be present in a 

 large quantity of grain. 



There are considerable differences between Stinking Smut and Loose 

 Smut; but, from the wheat-grower's standpoint, the chief one is that Stink- 

 ing Smut (Bunt) can be readily prevented by treating the seed wheat 

 before it is sown, whilst Loose Smut requires special treatment of the seed 

 for its prevention in the resulting crop. 



The minute black particles which are found adhering to a wheat grain, 

 and which are commonly called "smut," but which would be better called 

 "bunt," are the seeds or spores of a plant (a fungus), just as the grains of 

 wheat are the seeds of another plant. Fig. 3 illustrates a part of the brush 

 of a grain of wheat, and shows how very minute the spores are. Treat- 

 ment must be very thorough to kill these spores, as they cling to the fine 

 hairs, and when the grain is dipped bubbles of air are often caught amidst 

 the hairs and help to prevent the spores from being wetted and killed. Any 

 spores that retain their vitality after the treatment of the grain with the 

 fungicide, may germinate in the soil when the grain is sown. Under 

 suitable conditions they enter the young plant, grow with it, living on its 

 tissues, and finally cause the " hunted " wheat ear. 



The spores do not escape from the wheat ears in a powder, but are 

 enclosed in the ovaries and glumes, and although at first somewhat greasy, 

 they soon become dry and hard. The mass of spores in an ovary is known 

 as a " bunt ball " ; hence it is frequently spoken of as " ball smut," and 

 sometimes, on account of its hardness, as " stone smut." 



Fig. 5 shows the various stages during which a developing plant may be 

 attacked. 



The fungus growing in the plant reaches the developing ear, and pro- 

 duces its spores, forming the dark grain-like bodies (bunt balls) which take 

 the place of the normal grain (Figs. 1 and 2). 



* Compiled by Officers of the Biologica Branch. 



