162 



giving the first dressing is as soon as the haulm has 

 recovered from the bruising received during the mould- 

 ing-up. In wet and warm seasons disease becomes 

 apparent earlier than usual, and judgment must be 

 used as to the advisability of spraying small plants. 

 The necessity of commencing to spray early is in- 

 creased by the fact that when the weather is continu- 

 ously wet, and favourable to the development of 

 disease, it is difficult to get about the crop and use the 

 machine. 



The number of dressings necessary to render the 

 crop safe from serious injury is regulated by the nature 

 of the weather and the power the particular variety 

 has of resisting disease. In dry seasons one dressing 

 will prove efficacious, whereas in wet ones three may 

 be required. Varieties which are easily attacked 

 usually require two dressings. 



It has been suggested that one of the effects of 

 spraying the plants with sulphate of copper might be 

 to introduce copper into the tubers. Dr. J. M. II . 

 Munro made special analyses in connection with the 

 Warminster experiments with a view of ascertaining if 

 this were correct, and reported as follows : " Not a 

 trace of copper could be discovered by the most 

 delicate tests in the concentrated extract from over 

 one pound of tubers (previously reduced to ash) from 

 the various dressed plots." 



Lysol. 



It is hardly probable that sulphate of copper is the 



