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cresol, chlordinitrobenzene and nitrobenzene. Satisfactory infec- 

 tion was not obtained in pot experiments; this method was 

 therefore abandoned in favour of field experiments. 



The incorporation of chemicals with the soil in the field was 

 carried out with the Simar Rotary Tiller, great care being- taken 

 to ensure very thorough and even distribution. Results suggest 

 that the efficiency of the treatment depends on this thoroughness 

 of incorporation. During 1922 a selection of the chemicals tried 

 in 1921 and others were tested. From these sulphur was selected 

 in 1923 lor more extensive study as being the most hopeful 

 because of its efficiency and cheapness. 



In 1924, a year of very heavy disease, it was proved at 

 Ormskirk that when the dose of ground sulphur was increased 

 through 1, 2, 3, 4, 5, 10 cwts. per acre the degree of infection 

 was reduced in direct ratio from 73 per cent., the value for un- 

 treated soil, to 8 per cent, for an application of 10 cwts. per 

 acre. Doses greater than the latter did not produce propor- 

 tionate decreases of infection ; but there are reasons for thinking 

 that this small amount of disease in certain of the plots was clue 

 to recontamination of those plots later in the season. When the 

 results are represented in graphical form the straight line of 

 nearest fit to the experimental values cuts the horizontal axis at 

 a point representing 11.2 cwts. per acre of sulphur; 

 and, in the absence of secondary infection, this quantity of sulphur 

 should be slightly more than the minimum necessary to free the 

 Ormskirk soil of disease. 



On the heavy clay soil at Hatfield it was found necessary to 

 use much heavier applications of sulphur (about 40 cwts. per 

 acre) to ensure absolutely clean plots. 



Gasworks-spent-oxides, tried as an alternative source of 

 sulphur, proved rather less effective than ground sulphur when 

 equal quantities of sulphur were applied in each case. The result 

 was probably due to the unsatisfactory state of division of the 

 sample of spent oxides. 



Sulphur inoculated with Thiobacillus ihiooxydans showed no 

 increased efficiency over uninoculated sulphur on Ormskirk soils 

 and appeared less effective than the latter on the Hatfield clay. 



The elimination of wart disease in the field by sulphur and 

 sulphur compounds was not correlated with the degrees of acidity 

 produced and it would appear that some sulphur product other 

 than sulphuric acid is the active fungicidal agent. 



The sulphur treatment will be put to a large scale critical 

 test in 1925-6 ; but the results to date seem to show that a 

 feasible method of eradication of Wart Disease from contaminated 

 land may have been found. 



Many outbreaks are in gardens or allotments situated in the 

 midst of rich potato districts; but owing to legislation limiting 

 the movement of potatoes from relatively large areas surrounding 

 these outbrciks, they are the cause of great losses to neighbouring 

 growers. Hence it is economically possible to spend relatively 

 large sums of money in dealing with these small outbreaks which 

 would be out of the question if treatment at a proportionate cost 

 were to be applied to larger areas. The results described in 



