1922.] 



Potato Pink Bot. 



1129 



popular name from the fact that the cut surfaces of infected tubers 

 quickly turn pink when exposed to the air. It commences when 

 the potatoes are still in the ground and attached to the 

 parent plant, and has been found from the end of July onwards. 

 In most cases the attack in the tuber begins at the heel end, 

 because the fungus enters through the stalk, and it pro- 

 ceeds rather rapidly towards the rose end. Diseased tubers 

 remain firm, but of an india-rubbery consistency, and if pressed 

 exude a quantity of juice, while finally they become completely 

 rotten. They do not, however, develop cavities, as in the case 

 of Blackleg. A characteristic series of cciour-changes takes place 

 when affected tubers are cut open and exposed to the air and these 

 form an important character for diagnosing the disease 

 in the field. A pink colour begins to show a few minutes after 

 cutting, and within half-an-hour the whole of the diseased por- 

 tion becomes a deep salmon-pink. With an exposure of several 

 hours the cut surface gradually darkens and becomes purplish- 

 hrown or nearly black. 



Plants infected with the Pink Bot fungus show also indica- 

 tions of unhealthiness in the foliage, due to the presence of 

 mycelium in the stem and roots. This usually occurs rather 

 late in the season. The leaves become pale green or yellow and 

 ultimately collapse or fall off. The symptoms are on the whole 

 those of a Wilt, though the denuded stem somewhat resembles 

 those which have been severely attacked by Blight. Besting 

 spores of the fungus are found in the underground stems and 

 also in old diseased tubers, and in this way the contamination of 

 the soil is brought about. 



The losses caused in some of the western districts of Ireland 

 by Pink Bot may be very considerable, in some cases heavier 

 even than those due to Blight, and are greatest in crops grown 

 continuously or too frequently on the same land. 



Conclusion.— The discovery of Pink Bot need not alarm English 

 growers. As stated above, it is probably not an absolutely new 

 introduction, but has now been detected for the first time. 

 Its discovery is, however, of great importance, since if the view 

 be correct that Pink Bot" has existed in the country for several 

 years and been regarded as Blight, it is obvious that spraying as 

 a preventive would be a waste of time and money. In 

 Ireland it has been known now for many years but has 

 apparently not spread to any extent, and with proper rotation 

 of crops, care as to seed and precautions as to the use of town 



