. Bulletin of the Department of Agriculture. Agriculture; Agriculture. Contribution from the Bureau of Chemistry CARL L. ALSBERG, Chief. Washington, D. C. August 24, 1920 PICKERING SPRAYS. By F. C. Cook,1 Physiological Chemist, Insecticide and Fungicide Laboratory. CONTENTS. Introduction. Results of previous investigations. Purpose of present Preparation of sprays used Results of investigation: Potatoes Grapes Page. I Page 1 ; Results of investigation—Continued. 2 Apples 29 6 Cranberries 37 7 Suggestions for the preparation of Pickering spray on a commercial scale 42 S
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. Contribution from the Bureau of Chemistry CARL L. ALSBERG, Chief. Washington, D. C. August 24, 1920 PICKERING SPRAYS. By F. C. Cook,1 Physiological Chemist, Insecticide and Fungicide Laboratory. CONTENTS. Introduction. Results of previous investigations. Purpose of present Preparation of sprays used Results of investigation: Potatoes Grapes Page. I Page 1 ; Results of investigation—Continued. 2 Apples 29 6 Cranberries 37 7 Suggestions for the preparation of Pickering spray on a commercial scale 42 Summary 44 22 i Bibliography 46 INTRODUCTION. When, in 1916, the price of copper sulphate (bhiestone or blue vitriol) rose to 25 and 30 cents a pound in certain parts of the country, the United States Department of Agriculture began to receive many inquiries as to the possibility of controlling certain fungous diseases of fruits and vegetables, either by using sprays other than those containing copper or by reducing the amount of copper sulphate used per given amount of spray. Past work having failed to show any fungicides which could replace the copper sprays for certain important plant diseases and the search for a new spray appearing rather unpromising, it seemed advisable to seek a copper spray which was more effective per unit of copper than the standard Bordeaux mixture and at the same time not so caustic as to injure vegetation. Accordingly, the Bureau of Chemistry, in cooperation with the Bureau of Plant Industry and the Maine Agricultural Ex- periment Station, undertook an investigation to determine the com- parative efficacy of the so-called Pickering sprays, which had been 1 The author wishes to express his appreciation of .the cooperation he received from J. K. Haywood,. Bureau of Chemistry; from W. B. Clark, H. A. Edson, L. H. Evans, W. A. Orton, J. W. Roberts, E. S. Schultz, C. L. Shear, M. B. Waite, E. Wallace, and R. B. Wilcox, of the Bureau of Plant "Indu
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