CONTROL OF THE SAN JOSE SCALE 11 



OILS AND SOAPS 



No. 6. — Brown neutral oil. 



Volatility (4 hours at 110° C.) per cent__ 2.7 



Viscosity (Saybolt at 100° F.) seconds.- 116 



Specific gravity at 20° C 0.922 



Unsulphoiiated residue (38 N acid) per cent — 49 



No. 7. — Dark neutral oil. 



Viscosity seconds 105 



Unsulphonated residue (38 N acid) per cent— 75 



No. 8. — Red engine oil. 



Volatility per cent — 0. 4 



Viscosity seconds 230 



Specific gravity 0. 921 



Unsulphonated residue (38 N acid) per cent 50 



No. 9. — Eastern red engine oil. 



Volatility per cent 0. 7 



Viscosity seconds — 227 



Specific gravity 0. 903 



No. 10.— Potash fish-oil soap. b^voSSJe 



Water 22. 5 



Fatty anhydrides 66. 



Alkali (K 9 0) 11.4 



SUMMARY 



Lubricating-oil emulsions have a number of advantages over 

 lime sulphur when used for controlling the San Jose scale. The 

 chief advantages are economy, greater ease in spraying thoroughly, 

 and greater effectiveness against the eggs of the red spiders, tree 

 hoppers, and the fruit-tree leaf roller, and against aphids. 



The danger of injury to dormant trees from oil sprays, if prop- 

 erly made and used at the right time, is very slight. These sprays 

 must be used in the spring before the bud scales separate. Injury 

 may result if they are used later than this, but no injury has resulted 

 from low temperatures following sprays applied in the spring. 



In order to obtain a satisfactory control of the San Jose scale in the 

 Pacific Northwest, lubricating-oil sprays must be used at a dilution 

 containing 4 per cent of oil. This dilution only allows a fraction of 

 1 per cent of the scale to live, while complete mortality may be 

 obtained with 6 and 8 per cent dilutions. It is probable that the 3 

 per cent dilution would be effective if the infestation of the scale 

 were very light. Dilutions containing only 2 per cent of oil do not 

 give satisfactory control. 



When used at 3 or 4 per cent there is practically no difference in 

 the effectiveness of oils of the red engine and of the brown neutral 

 types, even though the latter oils are lighter. Oils with a sulphona- 

 tion test of 50 to 70 per cent may be used safely. The three types of 

 oil sprays tested — the cold-mixed casemate oil emulsion, the boiled 

 emulsion, and the miscible oil — gave very similar results. 



The boiled emulsion, made with soap, is readily broken down in 

 hard water, .and its use can not be recommended in the Pacific North- 



