1920.] 



The Distribution of Wart Disease. 



737 



It was not until 1907 that the serious nature of Wart Disease 

 was generally realised by scientists. It became obvious at that 

 time that it was increasing in intensity in infected districts, 

 although growers were not inclined to believe that the disease 

 would cause any commercial loss in the crop. 



In 1908 an inquiry made by the Board of Agriculture into the 

 nature and extent of the disease in England, Wales, and Scot- 

 land revealed that in certain areas, especially Lancashire, 

 Cheshire, Staffordshire and South Scotland, the disease was 

 extensive, and had been present for manv years, and that 

 certain varieties, viz., Conquest, Snowdrop, Golden W^onder, 

 and Langworthy, appeared to resist the disease, although 

 Up-to-Date growing alongside suffered severely. 



Before dealing with the way in which this second discovery 

 was made use of, it is necessary to pursue the history of the 

 spread of the disease. 



Spread in Recent Years. — In 1910, as in 1908, Wart Disease 

 was chiefly confined to the counties of Lancashire, Cheshire, 

 Staffordshire (and certain other counties in the Midlands), 

 South Scotland, with a few cases in North and in South Wales, 

 and isolated outbreaks in other parts, e.g., Huntingdon, 

 Cambridge, Middlesex, Berkshire, Cumberland and Yorkshire 

 (West Biding) . 



Although, after a farther period of three years, considerably 

 more Wart Disease cases were knovvm to exist in the country, 

 the disease being more widespread in the old infected parts 

 than hitherto, its actual spread to other parts of England was 

 limited to a few outbreaks in counties which had hitherto been 

 supposed free from disease, viz., Northumberland, Durham, 

 and Westmorland in the North, and Somerset and Wiltshire 

 in the South West. 



By the end of 1916 Wart Disease had attained a firmer hold 

 throughout the country and had spread in the former infected 

 districts, especially in Wales and the West (the result it is said 

 of planting seed from the infected districts of Lancashire) . 

 Outbreaks of the disease had also appeared in the extreme^ 

 South, viz., in Dorset and Hampshire, and also in the South 

 East (Kent), but generally the Eastern and Southern potato dis- 

 tricts still remained clean. 



A survey made at the end of 1919 shows that Wart Disease 

 is now widely spread throughout the whole country, and that 

 there is probably no county free from this disease. There is 

 no doubt that the disease has made steady progress east- 



