TJW 



B 



CIRCULAR No. 59 



JANUARY, 1929 



UNITED STATES DEPARTMENT OF AGRICULTURE 

 WASHINGTON, D. C. 



& REMOVAL OF SPRAY RESIDUE FROM APPLES AND 

 PEARS IN THE PACIFIC NORTHWEST 



By H. 0. Diehl, Associate Physiologist, Office of Horticultural Crops and Dis- 

 eases, D. F. Fisher, Senior Pathologist, Office of Horticultural Crops and 

 Diseases, Bureau of Plant Industry, United States Department of Agricul- 

 ture; Henry Hartman, Associate Horticulturist, Oregon Agricultural College 

 Experiment Station; J. R. Magness, Horticulturist, State College of Wash- 

 ington Agricultural Experiment Station; and R. H. Robinsocst, Chemist, 

 Oregon Agricultural Experiment Station 1 



CONTENTS 



Introduction : 



General aspects of spray-residue re- 

 moval : 



Cleaning fruit by wiping or brush- 

 ing 



Dry-cleaning apparatus 



Limitations of dry-c leaning 

 methods 



Cleaning fruit by solvent methods 



Diff used-spray washer 



Forceful-jet spray washer 



Flood washer 



Flotation 



Combination of overhead dif- 

 fused spray and flotation 



Tank dipping in boxes 



Deep submersion 



Alkaline-solution washer 



Page 



Page 

 Cleaning fruit by solvent methods — 

 Continued. 



Influence of temperature on ef- 

 fectiveness! of solution 9 



Adjustment and care of equip- 

 ment 10 



Methods of rinsing 10 



Methods of drying 11 



Apparatus and methods for de- 

 termining acidity 11 



Effect of cleaning methods on keep- 

 ing quality 12 



Arsenical injury 13 



Hydrcchloric-acid burning 14 



Chemical injury at the core 15 



Rot-producing spores and 



moisture 15 



Conclusions and suggestions 17 



INTRODUCTION 



Although not all of the problems involved in the removal of spray 

 residues from apples and pears in the Pacific Northwest have yet 

 been solved, it is now possible to form certain conclusions based on 

 the experimental work and commercial experience of the past two 

 years and to derive from them suggestions for future procedure. 



The removal of spray residue may be divided into two phases : 



(1) The actual cleaning of the fruit and (2) the influence of cleaning 



treatments upon fruit injury and storage diseases. Although the 



former is the ultimate objective, it can not be attained satisfactorily 



> unless the latter is given proper consideration. 



J Both aspects of the problem have been investigated at the labora- 

 tories of the Bureau of Plant Industry at Wenatchee. Wash., and by 

 the State agricultural experiment stations of Oregon and Wash- 

 ington. 



1 Joint contribution from the United States Department of Agriculture, the Oregon 

 Agricultural College Experiment Station, and tbe State College of Washingon Agricul- 

 tural Experiment Station. Prepared by the writers in cooperation from the results of 

 their independent investigations. The names of the writers are arranged in alphabetical 

 order without reference to seniority or their contributions to the preparation of this 

 circular. 



19095 c 



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