as MASSACHUSETTS HORTICULTURAL SOCIETY 



Proteciion. Protection by spraying is the usual recommendation 

 for the control of the disease of roses caused by Diplocarpon rosae 

 Wolf. Of the numerous fungicides recommended in literature 

 probably bordeaux mixture and ammoniacal copper carbonate are 

 the two most often mentioned. Statements to the effect that the 

 latter fungicide is as efficacious as the former are common in liter- 

 ature. Results of the following experiments conducted in 1917 

 indicate that ammoniacal copper carbonate is not as efficient as 

 bordeaux mixture for the control of the disease. A mixture of 90 

 parts finely ground sulfur and 10 parts powdered arsenate of lead 

 dusted upon the plants proved to be as efficient as bordeaux mixture 

 and its use rendered the plants far less unsightly than the latter 

 fungicide. Lime-sulfur solution, 1 part of the commercial con- 

 centrated solution to 50 parts water, was found to be more efficient 

 than ammoniacal copper carbonate and probably as much so as 

 bordeaux mixture and the sulfur-lead dust. However, lime-sulfur 

 discolors the foliage almost as much as bordeaux mixture. 



Experiments in the nursery. 



In the experiments performed in the nursery there were nine 

 rows of rose plants, each of a single variety, the following eight 

 varieties being involved: J. B. Clark, Gruss an Teplitz (2 rows), 

 Prince Camille de Rohan, Clio, Mrs. John Laing, John Hopper, 

 Madame Gabriel Luizet, and Margaret Dickson. A part of each 

 row of plants was included in each of the diiferent plats. There 

 were 450 plants in each of the five plats which were treated as 

 follows: plat 1, dusted with sulfur 90 parts, and arsenate of lead 

 10 parts; plat 2, sprayed with bordeaux mixture, 5-5-50; plat 3, 

 sprayed with lime-sulfur solution 1 to 50; plat 4, sprayed with 

 Hammond's copper solution,^ 1 to 100; plat 5, untreated. 



The first applications of dust and spray were made on May 31. 

 All of the buds had opened and most of the leaves were well de- 

 veloped on this date. Subsequent applications were made on June 

 12, June 23, July 4, July 24, August 2, and August 25. Final data 

 were recorded on September 13, the middle row (variety Clio) being 



1 Hammond's Copper solution is a cupro-ammonium wash containing according to the 

 manufacturer 3.05 percent metallic copper. 



