40 BULLETIN 100, TJ. S. DEPARTMENT OF AGRICULTURE. 



while both the adults and larvEe of ladybirds feed on plant lice. 

 Mr. E. K. Carnes, 1 experimenting in the State Insectary at Sacra- 

 mento, Cal., found that 20 adult beetles of Hippodamia convergent 

 averaged 21.8 aphides per day and that the larvae of this species each 

 consumed from 250 to 300 plant lice during their larval existence. 

 He found that adult females would deposit eggs for from a month to 

 six weeks, laying on the average 15 eggs per day and feeding on the 

 plant lice all the time. Essig 2 states that in the walnut orchards of 

 Ventura County, Cal., OUa abdominalis, the ashy-gray ladybird, is by 

 far the most beneficial insect in the natural control of the European 

 walnut aphis (Chromapliis juglandicola) . 



ARTIFICIAL CONTROL OF WALNUT APHIDES. 



The writer has been unable, save in one instance, 3 to find any pub- 

 lished account of artificial control tried or adopted for walnut plant- 

 lice. Until the year 1910 no such work seems to have been performed 

 along this line. 4 In August of that year Mr. P. R. Jones, late of the 

 'Bureau of Entomology, carried out a series of laboratory experiments 

 with a view to determining the efficiency of various washes against 

 these aphides. A small hand pump was fitted with an Eddy-chamber 

 nozzle and the applications made at a medium high pressure. Care 

 was taken that not enough pressure was exerted to kill any of the 

 "lice" by the force of the spray alone. Examinations were made 10 

 minutes after the applications. From these experiments the fol- 

 lowing results were obtained : 



Commercial tobacco extract No. 2, containing 40 per cent nicotine, at strengths of 

 1-1,040 to 1-2,048, effective; dilutions weaker than 1-2,048, not effective. - 



Commercial tobacco extract No. 1 containing about 4 per cent of nicotine at strength 

 of 1-60, effective; dilutions weaker than 1-60, not effective (1-80 partially effective). 



Commercial tobacco extract No. 1, at strengths varying from 1-60 to 1-200, com- 

 bined with a 3 per cent distillate-oil emulsion, effective. 



Commercial tobacco extract No. 2 at strengths varying from 1-1,000 to 1-2,650 com- 

 bined with a 3 per cent distillate-oil emulsion, effective. 



Commercial tobacco extract No. 1 at strengths varying from 1-60 to 1-200 combined 

 with a 2 per cent distillate-oil emulsion, effective. 



Commercial tobacco extract No. 2 at strengths varying from 1-1,000 to 1-2,620 com- 

 bined with a 2 per cent distillate-oil emulsion, effective. 



Distillate-oil emulsion at 2, 3, and 4 per cent strengths, effective. 



Commercial lime-sulphur, 1-50, combined with commercial tobacco extract No. 1, 

 1-100, effective. 



1 Sept., 1912. Carnes, E. K. Insectary Division Reports for the months of June and July, 1912. Mo. 

 Bui. Cal. State Hort. Com., v. 1, no. 10, p. 820-828. 



Some experiments with the common ladybird ( Hippodamia convergent), p. 821-826. 



» Apr., 1912. Essig, E. O. The walnut plant louse ( Chromaphis juglandicola [Kalt] Walker). Mo. Bui. 

 Cal. State Com. Uort., v. 1, no. 5, p. 190-194, figs. 72-73. 



Control, p. 192. 



a Cf. Biennial Crop Pest and Hort. Report 1911-1912, Oregon Agr. Coll. Exp. Sta. Jan. 10, 1913, p. 16.5. 

 " Blackleaf 40" and kerosene emulsion 10 per cent recommended. 



* Since going to press control experiments undertaken in the spring of 1913 in Southern California by 

 the University of California have been published in Circular 107 of toe Agricultural Experiment Station 

 of the University of California. 



