432 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



The Ortho brand of Western crude oil emulsion gave a 50 per cent 

 kill on the trees sprayed with the customary' 12 per cent strength of oil. 

 The results obtained from, both types of emulsions of the Western crude 

 oil in the dipping experiments gave som.e rather interesting figures show- 

 ing that the killing efficiency varied more or less directly with the per- 

 centage of oil in the mixtures. In regard to the figure of 97.7 per cent 

 kill obtained with the 15 per cent Ortho crude oil sam.ple it m.ight be 

 explained that all but one egg in one mass failed to hatch which would 

 m.ake the actual kill very close to 100 per cent. The results obtained 

 with the 1 2 per cent crude oil sam.ple on the trees were not entirely satis- 

 factory, in spite of the fact that the number of cull apples was reduced to 

 9.92 per cent total injury as compared with a check of 26.9 per cent total 

 fruit injury. The figures obtained from, the masses dipped in 15 per 

 cent strength would seem to indicate that this greater strength of oil is 

 needed to obtain satisfactory results from, spraying, especially since 

 under the ideal killing conditions offered by the dipping m.ethod the 

 strength of oil required was 15 per cent for good results. This is a point 

 which will be carefully investigated during the com.ing season. 



Crude oil emulsions are widely used in the apple orchards of the 

 Pajaro Vallc}- as general winter sprays, giving excellent results in the 

 control of the many scale insects as well as nturt.erous other resistant 

 overwintering insect fonns. In addition, these m.aterials produce mark- 

 ed tree stimulation. For these reasons the continued use of crude oil 

 emiulsion is highly desirable on the part of m.any growers and it would 

 undoubtedly becom.e even more so if found effective in controlling leaf- 

 rollers at a strength within the limits of reasonable costs. 



Strength Date 



(a) 5% Western crude oil- (Ortho) 



10% 



15% 



Check 



(b) 12%, Western cr.-.de oil-(Ortho) Feb. 3 



(a) 5% Penn. crude oil 



(emulsified the same as Ortho) 

 10% Penn. crude oil 

 15% 



(b) 12% Jan. II 



(a) 5% Western crude oil 



10% 



15% 



Check with 5% cresol soap 



(b) 10% Western crude oil 



(a) 5% Penn. crude oil 



10% 



15% 



(b) 10% Feb. 3 



(a) s%Western Shell distillate 



10% 



15% 



(b) 10% Feb. 3 



