■'.. 



CIRCULAR No. 295 



DECEMBER 1933 



UNITED STATES DEPARTMENT OF AGRICULTURE 

 WASHINGTON, DC. 



THE OBSCURE SCALE ON THE PECAN AND ITS 



CONTROL 



By Howard Baker, 1 assistant entomologist, Division of Fruit and Shade Tree 

 Insects, Bureau of Entomology 



CONTENTS 



Page 



Introduction. _ 1 



Nature of injury 2 



General description of the stages 3 



Life history and habits 5 



Natural control 8 



Parasites 8 



Predators 9 



Diseases 9 



Page 



Artificial control 10 



Dormant spray applications 10 



Summer spray applications 15 



Recommendations for control 16 



Formulas used in preparing lubricating- 



oil emulsions 17 



Specifications of oils used ^ 17 



Summary 18 



Literature cited 19 



INTRODUCTION 



Because of the prevalence of the obscure scale in Louisiana pecan 

 orchards, the increasing demands for recommendations for its control, 

 and the wide variation in the control measures that have been recom- 

 mended, a study of its biology and control was made from 1929 to 

 1932, inclusive, at the pecan insect laboratory of the United States 

 Bureau of Entomology at Shreveport, La. The results of these 

 investigations are reported briefly in this circular. 



The obscure scale (Chrysomphalus obscufus Comst.) 2 was first 

 described in 1880 by Comstock (I, p. 303), 3 when he found it attacking 

 the willow oak (Quercus phellos) in the District of Columbia, and was 

 first reported as a pest of the pecan by Herrick and Harned in 1909 

 (6) f when they found it attacking the pecan in Mississippi. This 

 scale is probably a native pest, as it has not been reported from any 

 foreign country. It has now been reported from nearly all of the ter- 

 ritory from Massachusetts south to and including Florida and west 

 to include Illinois, Kansas, Oklahoma, and Texas (fig. 1). It is 

 usually found on oaks and hickories but is occasionally found on other 

 plants. The pecan is a favorite host plant, and this scale insect is a 

 serious pest on both seedling and improved varieties in Texas, Louisi- 

 ana, Arkansas, Mississippi, and Alabama. It formerly attracted 

 only occasional notice, but, with the increasing importance of the 

 pecan industry, it has lately come into more prominence. 



In general, the measures recommended for its control have been 

 those which have proved satisfactory for related scale insects, but 

 in many instances they have been inadequate. Most writers (<•?, 

 7, 9) have quite generally agreed that lime-sulphur, at whatever 



1 The author expresses his appreciation of helpful suggestions received from G. F. Moznette of the pecan 

 insect laboratory of the U.S. Bureau of Entomology at Albany, Ga. 



2 Order Homoptera, family Coccidae, subfamily Diaspinae. 



3 Italic numbers in parentheses refer to Literature Cited, p. 19. 



4485°— 33 1 



