TREATMENT FOR CONTROL OF APPLE APHIDS. 55 



Efficiency of Miscible Oils against the Aphids. — Tests against the living 

 aphids with two brands of proprietary miscible oils showed a killing 

 efficiency of 100 per cent, for each of these. 



Action of Miscible Oils upon the Aphids. — The killing action of miscible 

 oils upon the aphids seems to be almost instantaneous. In fact on twigs 

 examined shortly after dipping no movement of the aphids could be 

 noticed. The action is evidently of a strictly chemical nature. 



Foliage Injury by Miscible Oils. — While spraying with miscible oils 

 for the control of San Jos6 scale is usually confined to the dormant or 

 late dormant season, our tests would indicate that this material, if perfect, 

 can be used at full dormant-season strength during the delayed dormant 

 period with no more injurj' to the foliage than results from the use of 

 lime-sulfur. At this period in tests conducted both in the laboratory and 

 in the field onty sHght tip injury resulted; but where the fohage had 

 developed to three-fourths of an inch or more, the injury from the use of 

 the miscible oils seemed to be shghtly greater than that resulting from 

 the lime-sulfur treatment. Even this was not serious and was readily 

 overcome as the season advanced. From the foregoing it is evident that 

 where the use of miscible oils for orchard sprajdng is practiced the most 

 economical time for application is during the delaj^ed dormant period, 

 when one application will serve for both the San Jos6 scale treatment and 

 aphid control. 



Conclusions. 



1. The delayed dormant period is usually indicative of the complete 

 hatching of apple aphid eggs. At this time the buds have expanded 

 from a quarter to a half inch. 



2. Lime-sulfur solution at full dormant-season strength is less than 

 10 per cent, effective against the living aphids when applied at the de- 

 layed dormant period. 



3. Lime-sulfur applied at the late dormant period, before the buds 

 split open and just before the hatching of the aphid eggs, appears to be 

 highly effective, under favorable conditions, in destroying the eggs, but 

 the elements of thoroughness of application and unfavorable meteoro- 

 logical conditions present such unoertainty as to results that this treat- 

 ment can hardly be recommended as an effective control. 



4. If lime-sulfur is to be used as a control for San Jose scale and no 

 special treatment for apple aphids is to be made later, best results against 

 aphids, if present, are likely to be obtained by a late dormant-season 

 application just before the eggs hatch. Treatment at this time should 

 also be thoroughly effective against the scale. 



5. The appUcation of the lime-sulfur (1 to 8) and nicotine sulfate 

 (i to 800) combination applied at the delayed dormant period gives 

 practicallj^ a perfect control for apple aphids and makes unnecessary a 

 separate earher appHcation of lime-sulfur for San Jose scale. The per- 



