H. WOKMALD 201 



of a "cover-spray"' to protect the stiginatic surface is out of the question, 

 therefore a wash to be effective must be applied before the flowers open 

 and must be capable of destroying the powdery conidial stage, or at 

 least must prevent the conidia from falling during the period through- 

 out which the flowers are open and receptive. 



Experiments have been tried in the open with the Lime-sulphur 

 Wash, which is frequently recommended for cases of Brown Rot, but 

 no favourable results have been obtained. "Winter- washing" with 

 Lime-sulphur failed to check a serious outbreak of the disease in the 

 following spring. Facilities for testing the value of Lime-sulphur as 

 a summer spray were kindly offered by Mr P. Man waring ^ of Hors- 

 monden, Kent, who permitted a plantation of Lord Derby trees (four 

 rows each with thirty-two trees), which had had a severe attack of the 

 Blossom Wilt in the previous year, to be used for experimental purposes. 

 Three rows were thoroughly sprayed with Lime-sulphur at "summer 

 strength" (s.g. 1-01) immediately before the flowers opened, the fourth 

 row remaining untreated and kept as control. Li May all the rows 

 showed a serious attack of the Blossom AVilt and no difference in intensity 

 could be detected between the unsprayed row and the rest; many of 

 the latter had 50 % or more of the trusses killed by the fungus, and the 

 numerous Monilia pustules on the dead spurs were apparently uninjured 

 by the spray fluid. 



This result is doubtless due to the fact that such a liquid as the 

 Lime-sulphur solution is unable not only to penetrate but to adhere to 

 the powdery pustules. Experiments carried out in the laboratory 

 showed that Lime-sulphur solution even when applied in the form of a 

 very fine spray with an atomizer immediately ran off from the pustules 

 which appeared totally unaffected by the treatment. 



Bordeaux Mixture applied similarly with an atomizer adhered a 

 little more readily but the majority of the pustules were not covered 

 by the spray. 



An Ammonium Sulphide solution containing soft-soap, as recom- 

 mended by Dr Eyre and Mr Salmon^ for use on the conidial stage of 

 the Erysifhaceae, was also tried in the same way. This wash did wet 

 the pustules which in consequence became brown on the surface and 

 lost their pulverulent appearance. The pustules themselves were not 



^ I take this opportunity of thanking Mr Manwaring for the facilities offered for 

 investigating the disease in his plantations. 



^ Eyre, J. Vargas and Salmon, E. S. The Fungicidal Properties of Certain Spray 

 Fluids. Journ. Agric. Science, Vol. vn. pp. 473-507. 



