THE POTATO 169 



quently found on the same plant they are some- 

 times confused. 



"The disease has caused most damage in gar- 

 dens or allotments where potatoes are grown every 

 year, but in a few cases there has also been serious 

 loss in potatoes grown on farms worked on a four- 

 course rotation. 



"The occurrence of the wart disease in the 

 affected districts is similar to that of the Finger- 

 and-toe disease which, on certain soils and in some 

 seasons, causes serious damage to turnips. Al- 

 though in the first instance only a few plants may 

 show the wart disease, it is almost sure to spread, 

 and the disease must be treated as a dangerous 

 enemy, which, if neglected, may entirely prevent 

 the profitable culture of potatoes where it occurs. 

 Land may be unfit for potato growing for as long 

 as six years after infection, and possibly for a much 

 longer period. 



"The diseased tubers or haulms contain number- 

 less 'spores' (the 'seeds' of the disease), which are 

 not only capable of infecting healthy potatoes the 

 following season, but appear to be able to lie dor- 

 mant in the soil for several years. 



"The diseased tuber is the usual source of infec- 

 tion and the spread of the disease from one hold- 

 ing to another is mainly to be attributed to the 

 planting of infected sets. 



"When disease appears it may, if neglected, 

 spread over a farm and render the soil useless for 

 potato growing in the course of a few years. It is 

 spread by manure, by the decay of affected haulms, 

 tubers and runners in the soil, and it may even be 

 carried from one field to another on implements and 

 boots. 



"Diseased potatoes must always be well boiled 



