EXPERIMENTS ON THE CONTROL OF APPLE SCAB AND BLACK 

 ROT AND SPRAY INJURY IN 1924.* 



By W. L. Dor AN 



The experiments of 1924t were planned with the object of securing further 

 data on the comparative efficiency of several materials and schedules in con- 

 trolling apple scab caused by Venturia inaequalis. In addition to this, some 

 attention was given to black-rot caused by Physalospora cydoniae, with a view 

 to increasing our knowledge of its economic importance, seasonal occurrence, 

 and control in Massachusetts. Data were also secured which, it is believed, will 

 assist orchardists in reducing the severity of spray injury on fruit and foliage. 



Materials and Methods. 



At Middlesex Fruit Farm, Gravensteins having a spread of about 35 feet and 

 a height of about 25 feet were sprayed, and Baldwins having a spread of about 

 30 feet and a height of about 25 feet were dusted. At both Harvard Fruit Farm 

 and Pine Crest Orchard only Mcintosh trees were used. At the former orchard 

 these trees are eight years old and about 15 feet in height and diameter, and at 

 the latter orchard they are 11 years old and larger in proportion. 



At Harvard Fruit Farm and Pine Crest Orchard, Friend sprayers were used 

 with a pressure of about 200 pounds. At Middlesex Fruit Farm an Arlington 

 X L Sprayer was used with a pressure of about 150 pounds. At Middlesex 

 Fruit Farm two spray rods were used. Spray guns were used at Pine Crest 

 Orchard and at Harvard Fruit Farm, two at the former and one at the latter. 



At Middlesex Finiit Farm liquid lime-sulfur, 1 gallon in 50 gallons, was used; 

 and in the other orchards dry lime-sulfur, 4 pounds in 50 gallons, was used. 



Lead arsenate was present in all sprays or dusts in the usual proportions for' 

 the pink and calyx applications and for the application about two weeks after 

 the calyx. 



The Bordeaux mixture used was of the 3-10-50 formula. 



Dry-mix sulfur-lime was made up to contain 8 pounds of sulfur, 4 pounds of 

 hydrated lime, and I/2 pound of calcium caseinate in 50 gallons of spray, as 

 described by Farley.** 



The copper dust used contained 11 per cent monohydrate copper sulfate. The 

 sulfur dust used contained 90 parts or 85 parts sulfur, and 10 parts or 15 parts 

 lead arsenate in 100 parts. Niagara Sulfo-dust without arsenic was used for 

 all applications except those specified above as receiving an arsenical. 



The dusting was done with Niagara power dusters. In dusting, the halves of 

 the application were not "split," that is, at each application each tree was 

 dusted from two sides. The dusting was done either early in the morning or in 

 the evening, in order to have the foliage moist and to avoid wind. 



Two Mcintosh orchards were dusted and two Mcintosh orchards were sprayed. 

 An orchard of Gravensteins was sprayed and an orchard of Baldwins was dusted. 



All plots were sprayed or dusted at least four times. The dates of applica- 

 tions were as follows in the Mcintosh orchards: prepink. May 5-7; pink. May 

 14-17; calyx, May 31 — June 2; fourth, June 11-16; fifth spray, July 14; fifth 

 dust, June 30 — July 1; sixth dust, July 14-15; seventh dust, August 9-11, On 

 the other varieties, the applications were made at about the same time, although 

 in the case of the preblossom and calyx applications, the Gravenstein orchard 

 received treatment a few days before the Mcintosh, and the Baldwins a few days 

 after the Mcintosh. 



* Acknowledpment. This work was done with the co-operation of the Nashoba Fruit 

 Producers' Association, in the following orchards : Mr. Albert Jenks' Middlesex Fruit 

 ^'arm. West Acton ; Mr. Stephen W. Sabine's Pine Crest Orchard, Groton ; and Mr. 

 Philip H. Babcock's Harvard Fruit Farm, Harvard. In scoring the fruit, assistance was 

 given by Professors A. I. Bourne, B. D. Drain, J. S. Bailey, and W. H. Thies of Massachu- 

 setts Agricultural College. Mr. W. P. Wharton furnished rainfall records. 



t For results of earlier experiments in Massachusetts, see : Mass. Agr. Expt. Sta. Bul- 

 letins 214 and 219. 



** Farley, Arthur J. Dry -mix sulfur lime. New Jersey Agr. Expt. Sta. Bui. 379. 1923. 



