116 



There is however nothing unusual in this. It is a common feature of 

 this rust disease, and only shows how likely an outbreak of the disease 

 is, once the conditions are favourable to it. 



The rust found upon oat crops is one that is well known so far 

 as I am able to say at present, in fact it would be remarkable if this 

 were not so. I hope to examine specimens later in the season that 

 will set at rest all doubts upon this head. From an examination of the 

 uredospores the species appears to be Puccinia coronata.* 



The conditions that favour the spread of the rust disease are warmth 

 and moisture. As these factors vary from season to season it is easy 

 to understand why the disease varies in intensity in different years. 

 It is sometimes said that rust has ' ' suddenly appeared " in a district. 

 Such a statement is rarely true, the fact being that it has been all the 

 time present. What is meant is that it has suddenly increased in in- 

 tensity. This is due to favourable weather conditions. It is very 

 necessary to bear this in mind in reasoning about the disease, other- 

 wise there is danger of arriving at wrong conclusions. 



The species of rust that attack the various cereal crops though 

 similar to one another are not always the same. The tendency of 

 recent research is toward the belief that each species of rust is very 

 particular about its host plant, and that although two rusts may 

 resemble each other very closely they are often found each to be 

 associated with a single crop or a very limited number of related crops. 

 From this it follows that we should be careful about confounding 

 rusts found on various crops. The rust of wheat is a different rust for 

 instance from that most common on oats. Yet if a crop of wheat 

 were found growing alongside oats and both were found to be rusty it 

 would be natural to think that both crops were suffering from the same 

 disease, if we did not allow for the abovementioned fact. Nevertheless 

 the chances are that the two crops would be suffering from different 

 diseases derived from quite different sources, having no connection 

 with each other. These facts are mentioned to put farmers on their 

 guard in reasoning about the occurrence and prevalence of rust. 



The principal interest centres in what can be done to minimise the 

 losses due to the disease. What one will do depends entirely on how 

 much he is losing and how much he fears he will lose. As before 

 remarked, the amount of oat rust at present is not such as in my 

 opinion to cause great alarm. But it is enough to justify making 

 inquiries and experiments as to how the losses can be minimised. 

 Those experiments could be most profitably carried out on private 

 farms and at the Experiment Farms located in various districts. I 

 would advise farmers to beware of experiments and opinions derived 

 from districts other than their own, unless it is quite certain that such 

 districts are similar in all respects to their own district. 



The experiments that in my opinion would be advisable relate to 

 trials of various varieties of oats, to the use of other sorts of winter 

 feed, and to the trial of ensilage. 



* This determination has since been confirmed. 



