136 INSECT PESTS 



serious and difficult to handle than the Blight where it 

 gains a hold and is due to a fungus known as Synchytrium 

 endohiohcum. It lives as a parasite within the cells 

 of the potato, the cells being stimulated into active 

 subdivision much like Club Root of turnips, the tubers 

 being entirely destroyed. Here again we are in the 

 hands of the invisible spore, which may remain dormant 

 m the soil for years ; it may be conveyed on the boots 

 of the grower from one place to another ; it may be dropped 

 by birds, or it may pass harmless through the body of 

 a pig if the animal has been fed on the spoilt tubers, 

 which latter by the way is a criminal offence. 



It has been said that Wart Disease is the most difficult 

 of all diseases to eradicate from the soil. This is mainly 

 for want of a cheap method, but in a bad case over a 

 small area the carboUc treatment should be effectual. 

 As stated above, the pest can come in so many ways, 

 and is most likely in the seed-tubers when planted, so 

 that disease-resisters should always be chosen wherever 

 it has occurred. Among earhes these are King George, 

 Great Scot and Conquest. Among lates try Abundance! 

 Admiral, or Langworthy. (See Plate 31.) 



Corky Scab {Spongospora subterranea) is a milder dis- 

 ease of potatoes, more prevalent in the wetter parts of 

 the country. It is usually confined to the outer skin, 

 but in severe forms penetrates the flesh and becomes a 

 canker. Steeping the seed if affected in a solution of 

 formahn (about a dessertspoonful to a gallon of water) 

 will clean it, and as regards soil, it should be ascertained 

 whether there is an excess of hme, which, as it happens, 

 favours this particular fungus. If so sulphate of ammonia 

 should be appHed. 



Dry or Winter Rot of Potatoes, caused by Nectria 

 solani, happens when the tubers are insufficiently dried 

 after storing, with the result that they shrink and collapse, 

 becoming in a short space of time a culture ground for 

 Other fungi. Kainit, if it can be got, is a good artificial 



