1-6 J ouDial oj :\griciilluri.\ Victoria. [lo Feb., ipii. 



PREVENTION OF POTATO BLIOHT BY SPRAYING. 



D. McAlfhie, Vegetable Pathologist. 



In the leaflet issued by the Department of Agriculture and Technical 

 Instruction for Ireland on the Prevention of Potato Blight, the value of 

 spraying is shown in the results of experiments, and the following statement 

 regarding its utility is made: — " The experience of recent years has con- 

 clusively proved that the loss caused by potato blight can be, to a great 

 extent, prevented by spraying — an operation which has now come to be 

 regarded as an essential part of the work connected with the successful 

 cultivation of the potato crop. The reports received by the Department 

 from a large number of districts show that those who take the trouble 

 to carry out the work properly are abundantly rewarded, while those who 

 neglect to spray suffer heavy loss, both in the quantity and quality of the 

 crop." 



Sulphate of Copper and Washing Soda Recommended as a Spray. 

 The spraying mixtures recommended are either of the two following : — 



1. Sulphate of copper or bluestone and washing soda. 



2. Sul[)hate of copper and lime. 



The former is recommended by preference for the following reasons : — 



1. It adheres longer to the foliage of the plants, and is not so^ 



readily washed off by rain. 



2. It is more easily prepared. 



3. It is not so liable to clog the nozzles of the machine, because if 



the mixture is carefully prepared there should be no 

 sediment. 



Preparation of the Mixture. 



The mixture is made in the following proportions: — ■ 



S lbs. sul|>hate of copper. 

 10 lbs. washing soda. 

 40 gallons water. 



The sulphate of copper is dissolved in a barrel or wooden tub, because 

 the solution has a corrosive action on metal. Pour into the barrel 35 

 gallons of clean water. If there is any grit or foreign material in the 

 water it should be strained through a piece of hessian, so that it does 

 not clog the nozzles of the sprayer. 



The 8 lbs. of sulphate of copper should be tied up in a piece of hessian 

 and moved about in the water in the barrel until the crystals are all dis- 

 solved. The operation is hastened if the crystals are previously ground. 



Next dissolve the 10 lbs. of washing soda in five gallons of water in a 

 separate vessel. Then pour the washing soda solution slowly into the 

 copper sulphate solution in the barrel, stirring continuously, and the mixture 

 is ready for use. If convenient to have hot water, both the sulphate of 

 copper and the washing soda can be more quickly dissolved, and the 

 required quantity of cold water can afterwards be added. A quarter of a 

 pound of Paris green mav be added to the 40 gallons if it is desired to 

 destroy grubs as well. There is no harm in dissolving the sulphate of 

 copper and washing soda in separate vessels and keeping them in that 

 condition for several days, but once they are mixed together, the mixture 

 should be applied immediately. The mixture deteriorates rapidly even 

 when held over for one day, and is then much more readily washed off the 



