UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 866 
Contribution from the Bureau of Chemistry 
CARL L. ALSBERG, Chief 
Washington, D. C. 
August 24, 1920 
PICKERING SPRAYS 
By 
F. C. COOK, Physiological Chemist 
Insecticide and Fungicide Laboratory 
CONTENTS 
Introduction 
Results of Previous Investigations . 
Purpose of Present Investigation . 
Preparation of Sprays Used . . . 
Results of Investigation: 
Potatoes 
Grapes 
Page 
1 
2 
6 
7 
22 
Results of Investigation — continued. 
Apples 
Cranberries 
Suggestions for the Preparation of Pick- 
ering Spray on a Commercial Scale . 
Summary 44 
Bibliography 46 
42 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1920 
