48 



L. Sibyl T. Jevvson and F. Tattersfiei.d. ''The Infestatiou 

 of Fungus Cultures by Mites." Annals of Applied 

 Biology, 1922. Vol. IX. pp. 213-240. 



Mites are a serious pest of fungus cultures. The species that 

 most frequently occur are Aleurobius farince and Tyroglyphus 

 longior, with an occasional infestation with Glyciphagus 

 cadaverum. 



They can be controlled by exposing the cultures to the vapour 

 of Pyridine, after which treatment the fungi can be sub-cultured 

 safely. An exact description of the application of the method is 

 given. (Commercial Pyridine is as effective as the pure material.) 



If these pests occur in laboratory apparatus, they can be 

 eliminated by the application of strong ammonia. Ammonia and 

 its vapour are very rapidly effective against mites, but they should 

 not be allowed to come into contact with cultures of fungi for too 

 long a period of time in too high a concentration. 



Pyridine is shown to have a slight toxic action to fungi, and to 

 inhibit growth completely in certain concentrations which, how- 

 ever, are not at all likely to be objectionable in practice, especially 

 if the treated cultures are sub-cultured. 



A brief analysis of the toxic action of Pyridine on both mites 

 and fungi is given. 



(a) In the case of mites, minute doses have so powerful a 

 paralysing action as to render it probable that Pyridine is specific 

 in its toxic effect to these pests. 



(b) In the case of fungi, the action of Pyridine upon the 

 germination and growth of Aspergillus niger was closely studied. 

 It is shown that up to about .25%, Pyridine has apparently very 

 little toxic action and no feeding effect, but that above this con- 

 centration the toxicity increases with great rapidity. It is shown, 

 however, that the toxic action is one of inhibition of germination 

 and that the neutralisation of the base up to 0.6%, the highest 

 concentration tested (even though spores have been exposed to its 

 action for three weeks), permits growth to take place rapidly. 

 Pyridine acts chiefly as a poison through its basic properties but 

 not by the change in the pH of the medium which ensues on its 

 addition. 



WART DISEASE OF POTATOES. 



LI. William B. Bkierley. ''Some Research Aspects of the 

 Wart Disease Problem." Report of International 

 Potato Conference, London, 1921. 



The empiricism of present control methods is emphasised. 

 The disease is a complex state depending upon the physiology and 

 genetical constitutions of the host and the fungus, and this dual 

 entity exists in relation to a changing environment. The several 

 factors in this complex and their relation to the immunity or 

 susceptibility of potato plants to wart disease, are discussed. 

 The problems under investigation at Rothamsted — tuber quality of 

 immunes and non-immunes, nature of immunity, germination and 

 infection studies, soil sterilisation, etc. — are indicated, and other 

 aspects of wart disease research suggested. 



