10 CIRCULAE 295, U.S. DEPARTMENT OF AGRICULTURE 



showed 3,946, or 13.28 percent of them, to be affected by disease. 

 An examination of scale-infested material from almost any southern 

 Louisiana pecan orchard at this same period of the year would show 

 a much greater percentage diseased. 



ARTIFICIAL CONTROL 



TVhile parasites, predators, and diseases do their share in holding 

 this scale insect in check, they cannot be depended upon to do so always 

 or as effectively as is necessary. Consequently, it is necessary to 

 develop some method of artificial control which can be depended on 

 in time of need. 



DORMANT SPRAY APPLICATIONS 



Diuing the last 3 years rubric a ting-oil emulsions, miscible oils, and 

 liquid lime-sulphur have been tested at a number of strengths and 

 applied at different times dining the dormant period and at the de- 

 lay e d-d orcn ant period. 



Preliminary experiments were carried out in two orchards early in 

 1930. the results of which indicated that (1) the obscure scale is 

 difficult to control effectively, (2) liquid Kme-sulphur, even at a dilu- 

 tion of 1 part of stock solution to 5 parts of water, and lubric a ting-oil 

 emulsions containing 2 percent of oil in the diluted spray are ineffec- 

 tive, giving practically no control, and (3) miscible oils, 1 part stock 

 solution to 15 parts water, and lubric a ting-oil emulsions containing 

 4 and 6 percent of oil in the diluted spray can be depended upon to 

 give a fair to moderate degree of, but not perfect, control. 



During the dormant season of 1930-31, lubric a ting-oil emulsions, 

 miscible oils, and liquid lime-sulphur were tested again. Three oils 

 of widely different characteristics were emulsified by two formulas 

 and applied at concentrations of 2, 4, and 6 percent of oil in the 

 diluted emulsion at three widely separated times during the dormant 

 period in two different orchards. Two miscible oils were tested at a 

 dilution of 1 part stock solution to 15 parts water, and liquid lime- 

 sulphur testing 34° Baume was used at a dilution of 1 part stock 

 solution to 7 parts water. The results of these experiments are 

 given in table 1. 



The results shown in table 1 indicate that (1) lubricating oils at 

 equivalent dilutions are about equally effective whether emulsified 

 according to 'formula 1 or formula 3, (p. 17); (2) about the same degree 

 of control may be expected from spraying at anytime during the 

 dormant season: (3) the characteristics of the oils used did not appear 

 to influence the degree of control, indicating that any of the oils fall- 

 ing within the range of those ordinarily recommended for use in dor- 

 mant spray work (8) 7 should be about equally effective; (4) 2-percent 

 lubric ating-oil emulsions are ineffective, not even giving a good con- 

 trol of the exposed scales; (5 > 4-percent lubric a ting-oil emulsions are 

 fairly effective, giving a good control of the exposed scales and a fair 

 control of those developing under old scale covers: (6) 6-percent 

 lubric ating-oil emulsions are reasonably effective, giving a good degree 

 of control of the scales developing under old scale covers as well as 

 of the exposed scales. The control effected by this dilution can be 

 considered commercially satisfactory, since this scale has only one 



7 Range of specifications ordinarily recommended for oils for use in dormant sprays: Viscosity (Saybolt 

 100° F.)T 90 to about 200 seconds; volatility, low: unsulphonated residue, not less than 50 percent. 



