DISEASES OF ROSES 89 



selected and the numbei* of infected leaflets counted on twenty 

 plants. The part of the row included in each plat consisted of 

 approximately sixty plants, and the data were obtained from every 

 other plant in the central area. Defoliation was not taken into 

 consideration. From observations it was determined that the 

 amount of defoliation varied directly with the percentage of leaflet 

 infection in the various plats. 



The percentage of diseased leaflets for each plat was as follows: 

 sulfur 90 parts and arsenate of lead 10 parts, 7.66; bordeaux 

 mixture 5-5-50, 8.51; lime-sulfur solution 1 to 50, 24.43; Ham- 

 mond's copper solution 1 to 100, 37.77; untreated 80. 



A point to be noted in the above experiment is the fact that the 

 plat treated with lime-sulfur solution was situated on low ground 

 where there was poor drainage. Owing to the heavy precipitation 

 throughout the season these plants were "subjected to more moist 

 conditions than those in the other plats which had better drainage. 

 Consequently it is probable that lime-sulfur is more efficient in 

 the control of rose black-spot than the above results would indicate. 

 This probability is further emphasized by the following experi- 

 ments. 



Experiments in the test garden of the American Rose 



Society. 



A somewhat similar experiment for the control of Diplocarpon 

 rosae was conducted in the test garden of the American Rose 

 Society at Ithaca, New York. Here the plants were arranged in 

 beds, there being on an average, four varieties of six plants each in 

 a bed. There were six plats, each of which included twelve beds, 

 treated as follows: plat 1, dusted with sulfur 90 parts and arsenate 

 of lead 10 parts; plat 2, sprayed with ammoniacal copper carbon- 

 ate; ^ plat 3, sprayed with lime-sulfur 1 to 50; plat 4, sprayed 

 with fungi-bordo 5-5-50;- plat 5, sprayed with Hammond's copper 

 solution 1 to 100; plat 6, untreated. 



' The ammoniacal copper carbonate solution was composed of 5 ounces of copper car- 

 bonate, 3 pints of ammonium hydroxid (sp. gr. 0.90), and 50 gallons of water. 



2 Fungi-bordo is a dry, finely ground mixture of anhydrous copper sulphate and hydrated 

 lime. It was used at the rate of 10 pounds to 50 gallons of water which is approximately 

 equivalent to a 5-5-50 bordeaux mixture. 



