IRISH GARDENING. 



67 



of liver-of -sulphur used in this way before finally 

 rejecting this substance for the treatment of the 

 niildew, especially in view of the frequent use 

 of this substance as a fungicide, and its con- 

 venience and cheapness for this purpose. The 

 primary object of this note is to call attention 

 to this mixture, as used in the 1915 experiments, 

 in the hope that it may be tried by other workers 

 during the coming season and its actual value 

 tested under a variety of conditions. 



The work was started at Long Ashton during 

 the summer of 1914, in consequence of a slight 

 outbreak of the disease in the plantations at the 

 Research Station. It was decided to attempt 

 to ascertain to what extent the disease could be 

 controlled by summer spraying, the point of view 

 taken being that if the summer stage of the 

 disease could be adequately controlled the 

 amount of the winter stage formed would be so 

 limited that, with the further reduction of the 

 latter by tipping, the outbreak the following 

 season ought to be reduced eventually to in- 

 significance. Details of the 1914 experiments 

 ha\ang already' been published,* only a short 

 summary need be given here. 



The procedure adopted in the first set of ex- 

 periments on the affected bushes was to apply, 

 firstly, a spray which would kill by direct 

 contact so far as possible the mycelium and 

 conidia present on the bush, and, secondly, a 

 protective spray to keep the parts on which the 

 fungus had thus been killed free from infection 

 from external sources. A number of fiuids of the 

 first type, i.e., '' hitting " or " contact " sprays, 

 were tested, including one composed of 4 lb. of 

 liver-of -sulphur and 20 lb. of soft soap in 100 gal. 

 of water. On each of the plots thus treated a 

 series of protective or "' cover " spraj^s, such as 

 Bordeaux mixture, lime-sulphur, &c., were 

 applied. The applications were made at the 

 end of July, the outbreak being a very late one. 

 None of the results was entirely satisfactory, the 

 mildew reappearing fairh' generally, although 

 only slightly. 



In the course of this experiment it became 

 evident that the "' hitting " sprays were all more 

 or less ineffective, because they failed to wet the 

 fungus uniformly owing to the presence of air 

 between the conidioj^hores and the conidia. The 

 importance of this iX)int has also been empha- 

 sised in the x>aper by Messrs. Ej-re and Salmon, 

 who, owing to this difiiculty, used their test 

 fluids made up with 1 per cent, of soft soap. 

 The \vriters, however, found that twice that 

 quantity of soft soa^o did not sufiice to give com- 

 plete wetting, when the fluids were tested on a 

 practical scale. Under those conditions liver-of - 

 sulphur in the 0.4 per cent, solution mentioned 



* Ann. Report of the Univ. of Bristol Agric. 

 and Hort. Research Station, 1911. 



above proved inefficient. Messrs. Eyre and 

 Salmon found that it failed in soap solutions of 

 half that strength, when the percentages of the 

 sulphur compound used were about the amount 

 stated. It is, therefore, probably correct to con- 

 clude that liver-of-sulphur used at the rate of 

 0.3 or 0.4 per cent, in aqueous solutions or in 

 soft-soap solutions is, at the most, of only 

 limited value against mildews. (It is possible 

 that a I per cent, solution might wet the less 

 fioury mildews, such as pea mildew, but fail with 

 American gooseberry-mildew. ) 



The failure of soft soap alone to give the spray 

 fluids under trial the necessar\^ degree of wetting 

 power led eventuall}' to the use of soft-soap-and- 

 paraffin emulsion. From previous spraying 

 trials against woolly aphis on apple trees it had 

 been found that with the comparatively hard 

 water at Long Ashton the most wetting com- 

 bination was an emulsion of paraffin in soft-soap 

 solution at the rate of 20 lb. of soap and 2 gal. 

 of paraffin to 100 gal. of water. With soft water 

 not more than 1.5 lb. of soft soap need be used. 

 This emulsion, both when used alone and when 

 various fungicidal substances were dissolved in 

 it, proved capable of completel}' wetting the 

 densest patches of mildew. Even when a fungi- 

 cide was not added to it, it appeared to possess 

 a marked toxic action on the mildew, the conidia, 

 so far as could be judged in the original trials 

 by a microscopical examination, being killed 

 after contact with it. Tlie results of subsequent 

 experiments tended to show that the emulsion 

 alone could not be relied on to kill the " summer 

 stage " completely, and on that account it was 

 eventually decided after trial to use it in con- 

 junction with liver-of -suljDhur for the main 1915 

 experiment. 



This experiment was an attempt to stamp out, 

 if possible, the " summer stage " of the mildew 

 from a fairly well-isolated gooseberry plantation 

 in the neighbourhood of Weston-super-Mare, 

 with the object of ascertaining if the disease 

 would reappear the following season after this 

 treatment supplemented b}^ winter tipping, and 

 if so, if the time of the outbreak was delayed 

 sufficiently for the fruit to escape infection. 



The fungicide used was the soft-soap-and- 

 paraffin emulsion referred to in a previous 

 paragraph, with the addition of liver-of-sulphur 

 at the rate of 31 tb. per 100 gal. of the fluid, 

 i.e., a 2 per cent, emulsion containing approxi- 

 mately 0.35 per cent, of liver-of-sulphur.* 



* The mixture is made as follows : — In 5 gal. 

 of boiling water 20 lb. of soft soap and 3^ ft. of 

 liver-of-sulphur are dissolved by constant stirring. 

 Two gal. of paraffin (preferably " Solar Distil- 

 late " brand) are forcibly sprayed into the hot 

 solution, using a garden syringe with a rose 

 attached for this purpose. For use add 19 gal. 

 of water to every gallon of concentrated emulsion. 



