Sfiiikiiii! Smut or Bunt in Wheat. 



75 



It is generally recognised that the threshing machine has a deal to do 

 with the scattering of the spores and the dusting of the grain. When a 

 wheat stack infected with bunt is being threshed, the beaters of the drum 

 will break the bunt balls, and consequently the spores in countless millions 

 will be scattered by the wind, and the wheat coming down into the bags will 

 also be dusted with them. When the same threshing machine is used for 

 another stack, which maybe free from bunt, there are plenty of spores left 

 about the machine to infect a new lot of grain. The grain in the bags 

 will necessarily be stored in a dry place during the summer, and the spores 

 cannot germinate until moisture is supplied to them when they are sown in 

 the soil. It is well known that such seed dusted with spores and kept dry 

 during the summer will produce bunted wheat in the succeeding crop if not 

 treated, and even if the seed is kept dry for three years in a bag the spores 

 will germinate and cause the disease all the same. Clean seed may also be 

 contaminated by passing through a seed drill which has been used for bunted 

 wheat, and the sacks in which the seed is stored may also be a source of 

 infection. They should be disinfected by dipping in the solution used for 

 treating the seed wheat, say 1 lb. of bluestone dissolved in 5 gallons of water, 

 even although the wheat has been treated, for the seed may be reinfected 

 through dirty bags. 



But if the spores were exposed to the vicissitudes of the weather, as in 

 the case of those falling upon stubble ground from the last year's crop, would 

 they live and infect the new crop ? BoUey'^ carried out experiments to 

 settle this point, and he found that when the seed was treated to prevent 

 any infection from that source, in no case were there any smutted heads. 

 He considered that the spores, having germinated, the conidia, even although 

 in the ground, Avere so minute that the probabilities were against their being 

 in the proper position to infect the young wheat plant at the proper time. 

 In every case where the seed was pickled there were no smutted heads, even 

 although the soil was smutted. The results of these experiments show that 

 spores falling to the ground lose their vitality the first season ; but it is 

 known that when bunt-balls remain unbroken in the ground and are broken 

 the second year the spores may infect the young wheat plant. 



Re-inpection of the Seed after Treatment. 



Reference has been made to the danger of re-infecting the treated seed 

 ' J returning it to smut-infested bags, or sowing it by means of a seed drill 

 not properly cleaned. In the case of bluestone, a thin film of the solution 

 coats the grain, when it is properly soaked, and this is known to protect it 

 against infection from spores on the grain itself, and from bunt-balls iu the 

 soil. But what happens when the grain receives a fresh coating of spores 

 after treatment, either from broken bunt-balls or dirty bags, is a natural 

 question to ask. This has been investigated by the late Mr. Farrer, and our 

 own experiments are at present under way, the results of which will be 

 available later. 



As early as 1899 Farrer- commenced experiments with various fungicides 

 for the treatment of stinking smut, and he found it necessary, at the same 

 time, to test the effect produced by bunt-balls left among the grain and soa\ti 

 with it. In treating the seed, if the bunt-balls are not removed in the process, 

 they are likely to be broken in the subsequent handling of the grain, and 

 possibly infect it afresh, even although all the loose spores on the seed may 

 have been destroyed. 



The first experiments were designed to ascertain whether, and to what 

 extent, the bunt-balls when crushed and treated with fungicides were capable 

 of infection. The seed used was free from spores to begin with, and taken 



