Erysiphc Polygoni. G. 0, Searle. 275 



A number of the infected leaves were picked and placed in a 

 warm moist atmosphere for twenty-four hours to encourage the 

 formation of conidia. Tlie leaves were then washed in large 

 cans of water until it became quite milky from 'the number of 

 conidia contained. This spore suspension was then sprayc^l 

 through a fine rose, as evenly as possible, over the seventy-seven 

 plots. Pre\'ious to spraying a very careful examination was 

 made but no mildew could be found on any plot. The weather 

 was dull but no rain fell for three or four days after inoculation. 



Examined on Sept. 2nd, a few minute patches of mildew were 

 found on nearly every plot. From Sept. 6th to Oct. 9th the 

 severity of attack was classified once a week in the following 

 manner: Marks were assigned each week to each plot, these 

 marks varying from o-io according to the severity of the 

 attack; the plots marked o were those on which no trace of 

 mildew could be found, and so on proportionately up to 10 

 assigned to the plots most severely attacked, and on which not 

 a single leaf could be found free from mildew. By Oct. 9th the 

 attack seemed to have attained its maximum severity, and on 

 Nov. 3rd all the roots were pulled, topped, cleaned and weighed. 

 On an average the plots contained fifty roots each. 



The following are the salient points of the results. 



No variety of Swede, Turnip or Rape was found to be wholly 

 immune. 



Only two varieties, both Turnips, were marked as low as " i " 

 when the weekly readings were averaged at the end of the trials. 



The Swedes were attacked more severely than the Turnips; 

 the Rape came approximately midway between the two in the 

 severity of the attack. The Turnips were attacked most on the 

 underside of the leaf. 



It was reported by nurserymen that, in the North of England 

 at any rate, Bronze Top Swedes were more liable to mildew 

 than Purple or Green Top varieties and that Purple Top Yellow 

 is more susceptible than Green Top Yellow ; this was not con- 

 firmed by the trial, a Green Top Swede being one of those 

 averaging 9^, whilst another Green Top averaged only 2\, two 

 Bronze Top varieties averaged 8. 



The plots being so small, too great an experimental error was 

 introduced to allow any reliable comparison of yields with 

 severity of mildew attack, though it is of interest to note that 

 the two highest yields, each 106 lbs. per plot, averaged in 

 marking 2 in one case and 2f in the other; these were both 

 Turnips. 



In 1914 one hundred and four varieties were obtained, in- 

 cluding all those previously tested, but owing to the outbreak 

 of war the trials came to an end. 



