16 Letters on the Diseases of Flants. 



Loose smut first appears at the time the wheat comes into flower, and this 

 fact is in itself almost a guarantee that this is the period at which it infects 

 the next crop. 



Bunt, on the other hand, does not break loose from its ball-like enclosures 

 until harvested and threshed. That is the period at which it infects the 

 next crop, either through immediate contact with healthy seed or by- 

 becoming disseminated on the land so as to infect the seed when sown. 



Treatment either with hot water for fifteen minutes at 130°-135° 

 Fahrenheit, or soaking in a weak solution of bluestone or sulphide of potash 

 will prevent the appearance of bunt. 



In case of loose smut of wheat, however, I still doubt if any of these treat- 

 ments can be guaranteed to do very much good. I have treated thousands of 

 samples of wheat with hot water for instance, and while I observe that 1 am 

 thus able to largely control the disease called bunt, the results as regards loose 

 smut are very uncertain — so uncertain that any success I may attain I am 

 inclined to put down to some unknown factor. For one thing it seems very 

 reasonable to suppose that the state of the weather at the time of blossoming 

 (i.e. time of appearance of the loose smut) must have a great influence on 

 the prevalence of the disease the next season, although it is difficult to 

 advance the precise reasons beyond what has been already said. 



It is not uncommon for me to receive letters stating that seed wheat 

 treated with solution of bluestone has produced a smutty crop. In most 

 such cases I find the disease to be loose smut, which is again confirmatory of 

 the comparative inefficiency of the above treatments so far as this disease 

 is concerned. 



I have found the most certain preventive measure to be the plucking and 

 destroying of all loose-smutted heads. I fancy the owner of a thousand 

 acres of wheat will smile at the idea of going through it and weeding out 

 and burning the smutted heads. That, however, will be because he does not 

 understand my meaning. To make it clear I will describe the method 

 adopted and successfully carried out for four years at Wagga. 



To begin with, the seed for the Wagga Experiment Farm was collected 

 during the years 1890 and 1891 from all parts of the world, and it is quite 

 safe to say that I received along with it quite a fair share of every 

 important wheat disease. Stud plots were started, and were located 

 as they should be, namely, on the side of the farm or paddock towards 

 the prevailing wind, or, if not, then at a distance from all other wheat. 

 Unfortunately this rule has sometimes had to be abandoned, but always, 

 I am now convinced, with disadvantage. Each stud plot, one for each 

 principal variety, was grown from selected seed. When ripe, and during 

 growth, the plants were inspected, and all the diseased ones removed 

 and destroyed. This gave a crop of healthy seed. The reason the windward 

 side of the field was preferred as a location for the stud plots was the fact 

 that in that position fewer spores, either of smut or other diseases, would 

 be blown on to the plants it was desired to improve by selection. They 

 would thus be kept all the more free from disease. A few of the very best 

 plants from each stud plot were reserved so as to secure seed for a similar 

 stud plot next year. The remainder (after all undesirable plants had been 

 culled out, see Fig. 19) was used as seed wheat next year, and produced a few 

 acres of as healthy wheat as could be obtained. The seed, being derived 

 from healthy plants, did not need to be treated with hot water or anything else, 

 SO this expense was saved. These few acres were subjected to a less rigid 



