VII 



POTATOES 211 



coloration which frequently runs upward for several 

 inches. Drying kills the organism, but the corrosive 

 sublimate treatment as used for scab is recommended. 



Wet Rot. This is also a bacterial disease, which 

 occurs in Western Australia and causes considerable 

 trouble in warm, damp seasons and also in storage. 

 Dark patches appear beneath the skin of the tubers, 

 and the entire interior becomes brown and slimy. All 

 diseased plants and tubers should be destroyed. If it is 

 desirable to use the tubers for feed for live stock they 

 should first be boiled, or the spores will be returned to the 

 soil and re-infect the new crops. Use clean seed and 

 rotate the crops. 



Scab. This disease is due to the fungus Oospora 

 scabies, Thax., and is widely distributed throughout 

 most, if not all, of the potato-growing countries of the 

 world. It is very abundant in the West Indies, Europe, 

 Africa, New Zealand, and the United States. The 

 surface becomes more or less roughened and scabby, and 

 its value is greatly reduced. The scabby condition may 

 be confined to the surface, or it may extend throughout 

 the greater part of the tuber. The fungus penetrates the 

 tuber, causing an irritation which results in the scabby 

 growth just referred to. Unfortunately the organism 

 will live in the soil for several years (five or seven), and 

 will also attack other plants, such as beets, turnips, 

 cabbages, carrots, etc. Alkaline soils and fertilizers are 

 said to be most favourable for its development. 



Crops which are subject to this disease should not 

 be put in soil known to be infected, but some other 

 crop should be used until the disease has had time to 

 die out. Use clean tubers for seed, and, as a precaution, 

 treat them with either corrosive sublimate or formalin. 

 The corrosive sublimate (bichloride of mercury) should 

 be dissolved at the rate of two ounces in fifteen 

 gallons of water. Put the potatoes into a sack or crate 

 and suspend in the solution for one hour and thirty 

 minutes. Spread and allow to dry. CAUTION : 

 Corrosive sublimate is poisonous, and must be kept 



