48 PROTECTION OF PLAJSTS, 1920-21 



sprinkled on the grain, which is shovelled well so that each grain receives a 

 coating of the disinfectant. I must point out here that some farmers have 

 achieved excellent results by sprinkling copiously. The disinfecting action of 

 formalin is only completely realised when the vapor is produced and in order to 

 ensure the effect of formaldehyde vapor on the grain it is necessary to cover it 

 with sacking for five or six hours. Experiments made by farmers have shown 

 that even if left covered for as long as twelve to eighteen hours there was no 

 injjLiry to the grain and the crop is healthy. 



Concentrated Solution. — This is a recent method which has the advantage 

 of avoiding the necessity of handling a large quantity of water. It is carried 

 out by spraying with a concentrated solution consisting of one pint of formalin 

 with one pint of water. This is sufficient for fifty bushels. The grain is shov- 

 elled well during the spraying and is then covered for several hours. For my 

 part I prefer the previous treatment, because it has given the best results in our 

 county demonstration experiments. 



The treatment with formalin we owe to the work of BoUey, Swingle, Genth- 

 er, Arthur and others, but it is not the only method in use. Before the use of 

 formalin came into vogue and towards the end of the nineteenth century, Ben- 

 edict Prevost had succeeded in controlling stinking smut of wheat by soaking 

 it in a solution of copper sulphate. Mathieu de Dombasle verified the metlaod 

 but the growers, believing this substance to be very poisonous, continued to use 

 a simple heating or sulphate of soda followed by heating. Kuhn again used the 

 method and Linhart perfected it. The copper sulphate treatment is now the 

 only one in use in Australia. 



Among the diseases of cereals we find two in which the organism does not 

 exist on the surface but lives over in the seed itself. These are the loose smut 

 of wheat and of barley. In this case, therefore, formalin treatment is not applic- 

 able, but Jensen discovered that by careful treatment with hot water these 

 diseases may be controlled. 



Hot Wate?- Treatment.— In this method it is necessary to work with a tem- 

 perature which will kill the organism without affecting the germination of the 

 grain. This is done by using three baths with a gradually increasing temper- 

 ature as follows : 



1. Soaking at 86° F. for 4 hours. 



2. Soaking at 112° F. for 15 to 20 minutes. 



3. Soaking at 129° F. for 10 minutes. 



The first bath facilitates the heat penetration of the later soakings which 

 are of much shorter duration because of the higher temperature. It is impoit- 



