90 MASSACHUSETTS HORTICULTURAL SOCIETY 



During the summer thirteen treatments were made on the 

 following dates: May 26, June 4, June 11, June 18, June 24, 

 July 3, July 13, July 20, July 31, August 9, August 21, August 29, 

 and September 9. 



Final observations were made on September 24. Due to the 

 fact that the plats did not contain the same varieties it was im- 

 possible to compare the treatments by determining the percentage 

 of diseased leaflets. Gross observations were made by the wTiter 

 who also obtained the opinion of the gardener and others not 

 directly interested in the work. The plants of the dusted plat and 

 those sprayed with fungi-bordo and lime-sulfur solution stood out 

 in sharp contrast to the other plants in the garden due to their 

 healthy leaves and heavy foliation. It was impossible to deter- 

 mine from gross observations which of these treatments was most 

 efficient. The plats treated with ammoniacal copper carbonate 

 and with Hammond's copper solution contained but slightly less 

 affected plants than the check, and marked defoliation occurred 

 in all three plats. 



From these experiments it would seem that lime-sulfur solution 

 1 to 50, bordeaux mixture 5-5-50, and the dust mixture consisting 

 of 90 parts finely ground sulfur and 10 parts arsenate of lead, are 

 three efficient fungicides for the control of black-spot of the rose, 

 while Hammond's copper solution and ammoniacal copper car- 

 bonate solution are much less efficient. Due to its ease of applica- 

 tion and to the fact that its use discolors the foliage less than the 

 other two, the sulfur-lead dust ^ is to be given the preference. 



Powdery-mildew. 



Powdery-mildew is one of the most common and injurious 

 diseases of the rose, especially of plants grown under glass. Out- 

 of-doors plants are commonly attacked, the Crimson Rambler and 

 related forms being especially susceptible. Varieties differ greatly 

 in susceptibility. The disease was held by investigators to occur 



1 The sulfur-lead dust was obtained from the Union Sulphur Company and was so finely 

 ground that at least 98 per cent would pass through a 200-mesh sieve. It was applied with 

 a hand duster. 



