UNITED STATES 



DEPARTMENT OF AGRICULTURE 



DEPARTMENT CIRCULAR 263 



Washington, D. C. 



June, 1923 



PRELIMINARY REPORT ON CONTROL OF SAN JOSE 

 SCALE WITH LUBRICATING-OIL EMULSION/ 



A. J. ACKERMAN, 



Entomologist, Fruit Insect Investigations, Bureau of Entomology. 



CONTENTS. 



Page. 



Recent increase of the San Jose 



scale In northwestern Arkansas — 1 



History of infestation 2 



Factors influencing increase of the 



San Jose scale 2 



Distribution of injurious infesta- 

 tions 3 



Seriousness of injury in Arkansas 



orchards 4 



Comparative susceptibility of apple 



varieties 5 



Control methods prior to 1922 5 



Spraying experiments in the fall of 



1921 6 



Page. 



Tests with several brands of lubri- 

 cating oil 8 



Weak dosages of lubricating-oil emul- 

 sion 9 



Use of oil emulsion for dormant 



spray in commercial orchards 9 



Summer treatments with oil emul- 

 sion 10 



Advantages and disadvantages of oil 



emulsion 1 2 



Spray injury 12 



Method of preparation 1 ."^ 



Soaps and oils 17 



Recommendations 1 i 



RECENT INCREASE OF THE SAN JOSE SCALE IN NORTHWESTERN 



ARKANSAS. 



The San Jose scale has increased in such alarming numbers during 

 the last two years in several localities of the Ozark region of Arkan- 

 sas as to threaten the destruction of the apple industry. During 

 I 1920 this pest was present in a large number of orchards and in the 

 fall of that year much fruit was spotted with the scale, though onljr 

 a few trees had been killed. Following the complete crop failure of 

 1921 the San Jose scale developed into the most serious problem fruit 

 growers of this section had ever faced. Many acres of trees were 

 dead by late summer and many orchards were so thoroughly infested 

 with the scale that it became necessary to check the pest before the 

 next growing season in order to save the orchards. Growers were 

 extremely discouraged in view of many failures to control the scale 

 with dormant sprays during the preceding two seasons. 



^The writer wishes to acknowledge his indebtedness to Leslie Pierce, of the Bureau of 

 Plant Industry, for his cooperation and assistance during the entire progress of this 

 investigation, and to W. W. Yothers, of the Bureau of Entomology, for his many helpful 

 suggestions on oil-emulsion sprays based on several years' experience in Florida. 



30836°— 23 1 



