340 Mosaic Disease of Potatoes. [July, 



(2) In the south, where the disease not only occurs in more 

 severe form but is apparently more liable to spread (perhaps 

 owing to earlier and more extensive attacks of aphides), 

 extra care should be taken as to " seed." Where the 

 disease occurs, no " seed " should be saved, but fresh 

 " seed" should be obtained from a good district in the 

 north of England or from Scotland or Ireland. 



(3) Where Mosaic is persistently troublesome, varieties 

 particularly subject to it should not be grown. 



(4) Early rogueing is of some value, but under ordinary farm 

 or garden conditions the amount of success obtained is 

 not commensurate v^ith the cost. In the case of new 

 varieties or seedlings the matter is different and special 

 methods are warranted. If rogueing is carried out with 

 extreme care and thoroughness, and if aphis attacks are 

 prevented by spraying with a good insecticide (such as 

 nicotine and soft soap) , complete success should be 

 possible. In the case of valuable crosses, the use of aphis- 

 proof cages might be considered. 



(5) Those who grow for wholesale " seed " purposes should 

 remember that, though the effect of Mosaic may be com- 

 paratively slight in the north , it is often more severe in the 

 south, and as the disease becomes known the demand for 

 Mosaic-free " seed " will increase. Disease-free stocks 

 should be therefore retained and worked up for " seed " 

 purposes. In the case of new varieties, it may pay to 

 isolate these from other stocks, rogue carefully, and even 

 spray with soft soap and nicotine in the summer months. 



