646 



Notes on Insect and Fungus Pests, [nov., 



ground level. As a rule, the injury caused is slight, but 

 occasionally, as in the case reported to the Board, the haulm 

 is killed. The tubers, however, are not attacked. Lime 

 should be applied to the infected land. 



A much more serious disease was reported from the neigh- 

 bourhood of St. Helens in Lancashire, namely, Potato Leaf 

 Blotch, a disease well known in Ireland and on the Con- 

 tinent, but not previously recorded in Great Britain. The 

 foliage is the part attacked, the parasite Sporidesmium 

 solani varians, Vanha, forming small scattered brown 

 patches on the leaves. These patches gradually increase in 

 size and fuse together, forming large, well-defined blackish 

 patches. Leaves that are attacked become black and die. 

 When the disease appears early in the season, the growth of 

 the tubers is seriously checked. Spraying with half strength 

 Bordeaux mixture is said to check the spread of the disease, 

 if applied on its first appearance. Diseased tops should, of 

 course, be burned, as the winter stage of the fungus is 

 usually present in quantity, and would endanger future 

 crops. 



A single case of Blackleg or Potato Stem Rot, caused by 

 Bacillus phytophthorus, was recorded in Herefordshire. 

 The potatoes in this case were entirely destroyed in the 

 manner shown in the accompanying illustration. The 

 variety was a pink kidney, Mr. Breeze, which had been 

 grown in the garden for two years. There was no disease 

 in the garden last year, and in another plot, planted this 

 year with seed from the same source, the crop is healthy. 

 Indeed, no similar case of disease has been observed on 

 the holding before. The manure was obtained locally, but 

 other potatoes, manured with the same material, are appar- 

 ently healthy. The particular plot on which disease occurred 

 had not been planted with potatoes for three years. Un- 

 luckily, the case was not brought to the Board's notice early 

 enough to enable them to obtain a photograph showing the 

 effect of the disease on the stem and the relation of the stem 

 to the diseased tuber. 



