240 Infestation of Fungus Cultures hy Mites 



3. If these pests occur in laboratory apparatus they can be ehminated 

 by the apphcation 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. 



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

 inhibit growth completely in certain concentrations which, however, are 

 not at all likely to be objectionable in practice, especially if the treated 

 cultures are subcultured. 



5. 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 w^as closely studied. It is shown that up 

 to about -25 per cent.. Pyridine has apparently very little toxic action 

 and no feeding effect, but that above this concentration the toxicity 

 increases with great rapidity. It is show^n, howes-er, that the toxic action 

 is one of inhibition of germination and that the neutralisation of the base 

 up to 0*6 per cent., the highest concentration tested by us (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 jwH of the medium which ensues 

 on its addition. 



REFERENCES. 



(1) Bales, N. B. (1917). Ann. App. Biol. iv. 29. 



(2) Newstead, R. and Duvall, H. M. (1919). Rev. App. Ent. A7, 91. 



(1918). Roy. Soc. Rept. of Grain Pests (War) Comm. No. 2. 



(3) Tatteksfield, F. and Roberts, A. W. R. (1920). J. of Agr. Sci. x. 199. 



(4) Henderson .Smith, J. (1921). Ann. App. Biol. viii. 27. 



(5) Brenner, W. (1914). Centr. Bald. Abt. 2, Bd. 40, 555. 



(6) LtTTZ, L. (1905). Bull, de la Soc. Bot. de France, L,u. 194. 



(7) Harvey, T. F. and Sparks, C. F. (1918). ./. Soc. Chem. Ind. xxxvii. 4 IT. 



(8) Brunton, T. L. and Tunnicliffe, F. W. J. Physiol, xvii. 272. 



(9) Fryer, P. J. (1920). Insect Pest and Fungus Diseases (p. 445). 



(10) Rept. of the Entomologist U.S. Dept. of Agriculture, Washington, Aug. I, 1921. 



(11) Morgan, G. I. and Cooper, E. A. (1912). 8th Inst. Congr. of App. Chem. xix. 



243. 



(12) Newton Harvey, E. Publ. Carnegie Inst, of Washington, No. 183, p. 131. 



{Received July 19th, 1922.) 



