36 



growth, with the result that the crops upon the plot were much 

 more free from rust than those untreated. 



A further experiment performed by Mr. Whelan in Gipps- 

 land, confirms this. In his report, he says : " In addition to 

 preventing rust, a weak solution of ferrous sulphate will cure 

 the rust. I marked a rust-infected wheat plant and syringed it 

 with a solution of ferrous sulphate (one oz. to a gallon of 

 water), with the result that all the rust had disappeared in 

 twenty-four hours ; nor was the plant again attacked for 

 fourteen days." 



It appears that this treatment keeps off rust for fourteen 

 days ; the period during which rust may be considered to 

 jeopardize the yield of grain is probably not more than one 

 month to six weeks, so that if during this period the crop 

 were to be sprayed three times with a dilute solution of 

 sulphate of iron, say 6 Ibs. to the acre, at intervals of a 

 fortnight, it is anticipated that it would effectually save the 

 crop. At this rate, the cost of material would be trifling, from 

 8d. to 15. per acre, and the cost of application from 2d. to 3^. 

 per acre, or is. 6d. at the outside. It would not need to be 

 applied every year, but only during rusty years. 



Dr. Cobb, of New South Wales, at the Rust Conference held 

 in Sydney in June 1891, remarked "with regard to cura- 

 tive measures, the fact of the Strawsonizer being good or not, 

 was only a question of time. I have settled beyond doubt that 

 we are able to recommend a solution to be used with the 

 Strawsonizer which will kill the spores of rust. Wheat has a 

 bloom upon it which prevents anything but the finest spray 

 from having an effect upon it. This may be a good thing, 

 because the rust will wet more readily, and if we can wet the 

 rust without wetting the wheat, it will be all the better." Dr. 

 Cobb, it appeared, had not tried sulphate of iron, but sulphate 

 of copper, and he advised that molasses, or treacle, should be 

 mixed with it. 



In 1892, at the Rust Conference held in Adelaide, Dr. Cobb 

 showed a figure of a piece of a wheat leaf that had been 

 sprayed with ammonia-carbonate of copper ; that is, carbonate 

 of copper dissolved in dilute ammonia. He said : " After a plant 

 has been sprayed with this solution, the diluted ammonia 

 evaporates and leaves the carbonate of copper in the shape of 

 an exceedingly fine powder. Consequently, when we examine 

 the surface of the sprayed plant with a microscope, we 

 instantly notice this deposit distributed .in patches. It is 

 clear that by spraying the wheat leaf we have dotted it with 

 tiny patches of poison. As long as the patches of poison 

 remain, they constitute a protection against the "infection that 

 occurs by means of the spores falling upon the sprayed leaf. 

 Even should a spore fall on a portion of the leaf where 

 there is no poison, growth may be prevented." In the 

 figure alluded to, spores are shown where germination had 

 been checked because their germ tubes had run against 

 and absorbed some of the poison. Dr. Cobb continued 



