470 Ftiinjici<Ud I'ropcrticH of (Certain Spraij-FLaids 



It is believed also that the alkaline nature of the solutions may aid 

 the fungicidal action of the sulphur, although the sulphur which is 

 deposited on the decomposition of the sulphides is believed to be the 

 chief fungicidal agent. In a recent publication on this subject, Foreman' 

 goes further than this as the result of a number of experiments with 

 germinating spores of Botryiis cinerea and S'phaerotheca mors-uvae, and 

 claims that the most potent fungicidal agent is the free alkali. From 

 this point of view it is interesting to find that caustic alkalies and alkaline 

 solutions have sometimes been used as fungicides. For example, 

 solutions of sodium carbonate ranging from 0-05 % to 2-5 % have 

 been found to inhibit the germination of the spores of certain fungi; 

 a 1 % solution of ammonium carbonate perceptibly hinders the germina- 

 tion of uredos pores'' . 



It would obviously be unsafe, however, to assume that the con- 

 centration at which a fungicide is able to inhibit the germination of 

 the spore is that at which it is fungicidal to the well-established 

 actively-growing fungus. It has been pointed out by Wallace, Rlodgett 

 and Hesler^ that a solution which gives satisfactory results when used 

 against spores in the laboratorj' requires a concentration several hundred 

 times stronger to control the same fungus when growing on the plant. 

 Foreman* records that a 0-16 % solution of caustic soda prevents the 

 germination of the spores of Bolrylis cinerea and Sphacrollieca mors- 

 uvae ; we have found, however, that a 0-3 % solution does not kill 

 well-developed patches of S. Humuli. It is clear that experiments 

 based on the behaviour of spores placed in the fungicide have little 

 practical value as indicating the strength at which the same substance 

 will be fungicidal when used against the giowing fungus on the j)lant. 



A substance of more recent introduction for use against "powdery 

 mildews" is iron sulphide. P. J. O'Gara speaks^ of a spray-fluid con- 

 taining 0-,38 % iron sulphide as being '' the standard summer-spray for 

 apple and rose mildew" in fruit-growing districts in Oregon, U.S.A. 

 In some field experiments carried out by one of us" in 1 91 1 iron sulphide 



' Foreman, F. W., "The Fungicidal Proportica of Liver of Sulphur" (Jmirn. Agric. 

 Science, m. 401 (1910)). 



- HoUrung, M., Handh. d. chew. Mill j)p. 49, CO. 



» Wallace, E., Blotlgett, F. M., and Hesler, L. R., "Studies of the Fungicidal Value 

 of Lime-Sulfur Preparations" {Cornell Univ. Agric. Erper. Station. Bull. 2!I0 (1911)). 



' Foreman, F. W., loc. cil. 



' Leaflet, Rogue River Valley, Medford, Oregon (1911). 



' Salmon. R. S., "Report on Keonomic Mj'cology" {Jouni. S.F. Agric College, xxi. 

 p. 346 (1912)). 



