AUO 



/ CIRCULAR No. 175 September, 1931 



UNITED STATES DEPARTMENT OF AGRICULTURE 

 WASHINGTON, D. C. 



EXPERIMENTS FOR THE CONTROL OF THE SAN JOSE 



SCALE WITH LUBRICATING-OIL EMULSIONS 



IN THE PACIFIC NORTHWEST 



By E. J. Newcomer, Senior Entomologist, and M. A. Yothers, Associate Ento- 

 mologist, Division of Deciduous Fruit Insects, Bureau of Entomology 



CONTENTS 



Page 



Introduction 1 



Spraying experiments in 1923 3 



Spraying experiments in 1924 4 



Spraying experiments in 1925 6 



Spraying experiments in 1927 — 8 



Page 



Composition of spray materials 9 



Oil emulsions and miscible oils- 9 



Oils and soaps 11 



Summary 11 



INTRODUCTION 



The San Jose scale (Aspidiotus perniciosus Comstock) has been 

 gradually increasing in many parts of the Pacific Northwest, until 

 the loss of fruit caused by this pest has become very noticeable. This 

 increase has not been due to a failure of the lime sulphur to kill the 

 scale, although there may be particular cases where this has occurred. 

 It has been due chiefly to an increasing carelessness in applying the 

 spray. The trees are becoming larger and more difficult to spray, the 

 spray guns generally used are sometimes handled improperly, and 

 men of the type employed for this kind of work appear less inclined 

 to be thorough than formerly. There have also been orchards in 

 which the customary annual dormant application has been omitted for 

 one or more years, in consequence of which these orchards have be- 

 come seriously infested with the scale, the infestation spreading to the 

 surrounding orchards. 



The successful use of lubricating-oil emulsions against the San Jose 

 scale in the Middle West a number of years ago, in place of lime 

 sulphur, greatly increased the popularity of oil sprays in the West. 

 For this reason, and because of the increase in the scale, a series of 

 tests was made by the Bureau of Entomology at Yakima, Wash., in 

 order to find out whether a lubricating-oil emulsion could replace 

 lime sulphur as a scale spray and, if so, at what strength it must be 

 used. 



Lime sulphur, while very effective, has several drawbacks. It is 

 bulky and is disagreeable to handle on account of its caustic effect 

 on the face and hands. A few drops of spray in the eyes of the 



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