34 



Insect, Fungus, and other Pests. [april, 



of the symptoms and development of the complaint. Up to 

 the present no cause can be assigned for "Sprain," but it 

 appears to be of a physiological nature, and, if so, the 

 name "Sprain," which suggests a mechanical cause, is not a 

 very suitable one. 



One curious case in connection with "Sprain " was reported 

 to the Board. A correspondent from Chester forwarded a 

 potato which he believed was suffering from this complaint. 

 Upon investigation this proved to be a case of arrested 

 Winter Rot (Leaflet 193). For some unknown reason the 

 disease was stopped in its development, and instead of run- 

 ning its entire course and causing a complete wet rot, it 

 simply produced slight rifts in the flesh of the tuber, accom- 

 panied by the discoloration of the tissue in places. 



Collar Fungus. — A disease respecting which the Board 

 have received many complaints is that known as Collar 

 Fungus. Strictly speaking, this is an incorrect and unscien- 

 tific name, and merely implies that the collar of the plant is 

 affected. Hence a certain amount of confusion appears to 

 have arisen. Occasionally the words are used for the para- 

 site Armillaria mellea, WahL, otherwise called Tree Root 

 Rot (Leaflet 174). This is one of the most abundant and 

 widely distributed of British toadstools, and grows in dense 

 clusters round the roots of living trees and dead stumps. But 

 there is another disease known as Gooseberry Collar Fungus, 

 which is due to Cytosporina ribis, P. Magnus. This latter 

 parasite has also been recorded as causing the disease 

 in Holland (Van Hall in Annales Mycologici, Bd. 1, 

 I 9°3> P' 5°3)' Bushes attacked by this disease often die 

 somewhat suddenly and for no apparent reason. A careful 

 examination of the bush shows that the bark of the stem 

 just above the ground line is browned and dead. The fungus 

 fruit in such cases may be seen in the form of small black 

 bodies embedded in the bark, but in some cases the larger 

 branches of the root are also attacked. In other cases, how- 

 ever, the disease seems to affect one branch to begin with 

 and to spread gradually until in one or two seasons the tree 

 is killed. It does not spread continuously through a garden, 

 but appears irregularly among the bushes, in a manner that 

 suggests a wound fungus. Perhaps for this reason fruit 



