1921.] 



Prevention of " Bunt " in Wheat. 



1015 



It will be seen from the table that the severity of the attack 

 of " bunt " in part A of the field varied from 7.2 per cent, to 

 21.4 per cent. — an average of 12.8 per cent., and in part B of 

 the field from 0.5 per cent, to 4.1 per cent. — an average of 1.8 

 per cent. The cultivation and manuring of both parts of the 

 field had been the same for the wheat crop, though the cropping 

 had been different in 1917.* It would appear, therefore, that 

 the greater severity of attack in part A of the field was due to 

 some circumstances favourable for infection. Other cases are on 

 record where wheat sown earlier in the autumn has been less 

 severely attacked than similar seed sown later. 



This severe natural outbreak of " bunt " provided us with 

 excellent material for producing artificially severe outbreaks of 

 " bunt " for experimental purposes. The " bunted " grains 

 collected from the crop in 1918 were broken up and mixed with 

 a certain amount of healthy seed from the same crop. After this 

 admixture, the seed, as seen by the naked eye, was more or 

 less discoloured, the end of the grain which bears a tuft of hairs 

 being noticeably darkened. On microscopical examination, it 

 could be seen that this discoloration was due to myriads of the 

 " bunt " spores adhering to the surface of the grain, the tuft of 

 hairs often being clogged with a dark mass of spores. Such arti- 

 ficially contaminated seed was used in the Field Experiments 

 carried out in 1919 and 1920 which are described below. As will 

 he seen, this seed, when sown without being treated, produced a 

 crop very severely affected with " bunt." while treatment of 

 the seed with certain substances killed the " bunt " spores 

 adhering to the seed, which consequently produced a healthy crop. 



Methods of Treating Wheat Seed. — The practice of trea ting- 

 wheat seed with a solution of copper sulphate (Bluestone) — an 

 operation often called " pickling " — has been commonly adopted 

 by farmers in this country for manv years. The strength of the 

 solution advocated for this purpose varies from one per cent. 

 (1 lb. copper sulphate to 10 gal. water) to ten per cent. (10 lb. 

 to 10 gal. water) and 1 gal. of the solution is used to the sack of 

 wheat. In the writers' opinion, the solution used at this rate 

 is insufficient to wet all the grains (devils). 



In the autumn of 1920 a sample of wheat (variety " Bed 

 Standard ") which had been pickled by a farmer in Kent with a 

 10 per cent, solution of copper sulphate, using 1 gal. to the sack, 

 was sent together with an untreated sample of the same seed 



* A had been cropped with potatoes, and B half with clover and half 

 with sainfoin. 



