1909.] Insect, Fungus, and other Pests. 



33 



Sprain in Potatoes. — Several complaints have reached the 

 Board respecting the losses caused to potato growers from 

 the ailment known as sprain in pota- 

 Notes on Insect, toes » anc * ^ 18 asserted that cases of it 



Fungus, and other are becoming more frequent and are 

 Pests. causing some anxiety in Scotland 



and elsewhere. Considerable uncer- 

 tainty prevails respecting this ailment, and not only is the 

 cause unknown, but even the symptoms are not always agreed 

 upon. The following points, however, appear to be settled. 

 When the potato is cut through the middle, brown spots are 

 found, which one correspondent has described as like the 

 currants in a currant loaf or scone. When the potato has 

 been cooked, the spots do not blacken, but can be picked out 

 almost like pellets. The cropping of the potatoes is not 

 affected, and the ailment is found in well-proportioned tubers. 

 Nor is there any appearance in the haulm to indicate the 

 presence of "Sprain," though according to another corre- 

 spondent the haulm of the potato is darkened and covered 

 with a white scale when the tubers are beginning to be 

 attacked. The ailment develops in the pit, and in one case 

 where part of a crop was sold off the field, and part was put 

 into pits, the former was slightly and the latter seriously 

 affected. It starts at the "heel end" of the potato. 



The varieties likely to be able to resist "Sprain" are a 

 subject of inquiry, but the Board are informed that practically 

 every variety is liable, though British Queen is particularly 

 susceptible. The ailment is usually found on a gravelly, but 

 sometimes on a sandy soil, and it is said to be unknown on 

 a stiff soil. It has been suggested that it is due to a deficiency 

 of potash or lime in the soil, but at least one case has been 

 quoted to the Board in which a field has been affected where 

 these ingredients were not lacking. The weather has a mate- 

 rial effect on the progress of the ailment, for it grows much 

 worse in dry, hot seasons, while in damp years it is very 

 little known. Finally, there is no evidence that it is conveyed 

 by the seed, and sprained potatoes have been planted over 

 and over again without any bad results. Further informa- 

 tion is clearly desirable, and the Board would welcome any 

 other communications which would add to their knowledge 



D 



