APPLE POWDERY MILDEW. 11 



chamber nozzles of the " driving-mist " type were always used. One 

 line of hose was operated from the top of the sprayer, where special 

 attention was directed toward covering the terminal branches in the 

 tops of the trees and the outside parts of the trees. Another line of 

 hose was operated from the ground and directed against the interior 

 parts of the trees and upward against the under side of the leaves. 

 In this manner an endeavor was made to cover completely all of the 

 vegetative and fruit surface on each tree and obtain as complete pro- 

 tection as the different spray materials could afford. The details of 

 the experiments are presented in Tables I to IV. 



The materials tested are listed belcw, with a statement as to the 

 manner of their preparation or dilution. In connection with each is 

 given the formula number referred to in the spraying schedules. 



List of the spray materials tested, showing the composition of the formulas 



used. 



Formula 1. — Commercial liine-sulphur, 34° Baume, diluted li to 50. 



Formula 2. — Commercial lime-sulphur, 34° Baume, diluted 1 to 50. 



Formula 3. — Commercial lime-sulphur, 34° Baume, diluted 1 to 75. 



Formula 4- — Commercial lime-sulphur, 34° Baume, diluted 1 to 100. 



Formula 5. — Self -boiled lime-sulphur, 8-8-50. Add 8 pounds of sifted sulphur 

 to 8 pounds of stone lime, slaking in a barrel. Stir well, and add sufficient 

 water from time to time to keep it from burning. After ebullition ceases, 

 'dilute to 50 gallons and strain into the spray tank, when it is ready for use. 

 In practice it is best to make up enough for 150 to 200 gallons at once. 



Formula 6. — Iron sulphid (Ballard's formula). Dissolve 10 pounds of iron 

 sulphate in a barrel containing 50 gallons of water. Add lime-sulphur solution 

 until no more precipitate forms. Allow the precipitate to settle and drain off 

 the supernatant liquid. Again fill the barrel "with water, stir up the precipitate, 

 and allow to settle, and then drain off the clear liquid as before. Continue this 

 washing process until the yellow color disappears from the clear liquid. Make 

 up to 50 gallons for stock solution. For spraying, stir the stock solution well 

 and dilute 10 gallons in 90 gallons of water to make 100 gallons of spray. 



Formula 7. — Iron sulphid (Wenatchee formula). Slowly- add 2 pounds of 

 granulated iron sulphate to 100 gallons of water in the spray tank, keeping the 

 liquid well agitated. The iron sulphate goes into solution very quickly. Add 3 

 quarts of lime-sulphur solution (at a strength of 34° Baume) and use imme- 

 diately. 



Formula 8. — Colloidal sulphur. 1 Dissolve one-half pound of cheap glue in hot 

 water and add to 50 gallons of water in the spray tank. With the agitator run- 



1 This formula was adapted from a rather meager description of a method for pre- 

 paring colloidal sulphur contained in the Gardener's Chronicle, Aug. 7, 1915, by J. M. 

 Hector and S. J. M. Auld, of University College, Reading, England. They employed 

 this material against American gooseberry mildew at Heston, England, but a complete 

 report of their work has not been published. In a letter to the writer, dated Mar. 

 10, 1916, Prof. Hector furnished the formula used by them. It differed from the 

 one here described in that they employed gelatine instead of glue and hydrochloric acid 

 instead of sulphuric acid, and they made up a stock solution, which was diluted for spray- 

 ing. Prof. Hector stated that the chief objection to its general use was its expensiveness. 

 However, by the substitution of glue and sulphuric acid, as employed in formula 8, its 

 cost is greatly reduced. The formula as used at Wenatchee has been satisfactorily em- 

 ployed against apple scab in the Willamette Valley, Oreg., and against prune brown-rot 

 in Clarke County, Wash., in experiments carried on by the Office of Fruit-Disease Investi- 

 gations. 



