Page 30 



be made and results checked. Dipping 

 the infested apple twigs was resorted to 

 rather than spraying, in order to insure 

 uniformity of treatment, as by the lat- 

 ter method any variability of applica- 

 tion might lead to an improper inter- 

 pretation. On examination, shortly af- 

 ter the infested twigs were brought in 

 from the field, it was impossible to 

 make any estimate of the probable num- 

 ber of eggs that would hatch, since a 

 large percentage of the eggs were ap- 

 parently dead from some cause, as in- 

 dicated by their shriveled condition. 

 Twigs of as nearly the same size and 

 degree of infestation as possible were 

 selected for insecticide treatment and 

 check, the average length of the twigs 

 being about eight inches. No definite 

 percentage of efficiency can be given 

 for the tests against the eggs. The re- 

 sults should be taken as merely com- 

 parative and in the way of a generaliza- 

 tion, and are perhaps in need of further 

 verification both in the laboratory and 

 under field conditions. The tests against 

 the unhatched eggs were begun when 

 the buds were in the late dormant con- 

 dition and at such a short time before 

 hatching occurred that it was impos- 

 sible to carry out verification checks. 

 The results are given in the following 

 table: 



BETTER FRQ IT 



2. Lime-sulphur solution at full dor- 

 mant season strength is less than 10 per 

 cent effective against the living aphids 

 when applied at the delayed dormant 

 period. 



3. Lime-sulphur applied at the late 

 dormant period, before the buds split 

 open and just before the hatching of 

 the aphid eggs, appears to be highly ef- 

 fective, under favorable conditions, in 

 destroying the eggs, but the elements 

 of thoroughness of application and un- 

 favorable meteorological conditions 

 present such uncertainty as to results 

 that this treatment can hardly be i-ec- 

 ommended as an effective control. 



4. If lime-sulphur is to be used as a 

 control for San Jose scale and no spe- 

 cial 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 ef- 

 fective against the scale. 



5. The application of the lime-sul- 

 phur (one to eight) and nicotine sulph- 

 ate (one to 800) combination applied at 

 the delayed dormant period gives prac- 

 tically a perfect control for apple 

 aphids and makes unnecessary a sep- 

 arate earlier application of lime-sul- 



rOMPARATlVE EFFICIENCY OF LIME-SULPHUR AND MISCIBLE OILS AGAINST APPLE 

 APHID EGGS IN THE LATE DORMANT PERIOD UNDER LABORATORY CONDITIONS. 



March, 1020 



mant period, should result in practic- 

 ally a perfect control of apple aphids 

 also. 



7. Delayed dormant applications of 

 full dormant season strength lime-sul- 

 phur, lime-sulphur and nicotine sulph- 

 ate combined, and miscible oils, if per- 

 fect, can be made without material in- 

 jury to apple foliage. Even when the 

 the foliage is considerably more ad- 

 vanced, little severe injury usually re- 

 sults. This fact, if taken into account, 

 might make unnecessary separate ap- 

 plications for early and late budding 

 varieties. As the foliage becomes more 

 advanced, however, the success of the 

 treatment involves greater difficulty, 

 since the aphids are very difficult to 

 reach when they have the spreading 

 leaves for protection. 



8. The action of lime-sulphur in de- 

 stroying both the aphid eggs and living 

 insects appears to be mainly mechanical 

 by sticking them to the twigs. 



9. The action of nicotine sulphate in 

 killing the living aphids is slow, requir- 

 ing from about half an hour to twenty- 

 four hours or more for different indi- 

 viduals. Death appears to be due to 

 paralysis. 



10. Miscible oils are practically in- 

 stantaneous in their killing action 

 against the living aphids. The action 

 is probably of a chemical nature. 



Acknowledgments 



The writer is greatly indebted to Mr. 

 A. I. Bourne of the Massachusetts Ag- 

 ricultural Experiment Station staff for 

 assistance in carrying out the insecti- 

 cide tests, and to Dr. H. T. Fernald for 

 his kind suggestions and assistance. 



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. 



phur for San Jose scale. The percent- 

 age of efficiency will depend mainly 

 upon thoroughness of application. 



6. The ordinary dormant season 

 treatment of apple orchards with misc- 

 ible oil against San Jose scale, if ap- 

 plied thoroughly at the delayed dor- 



! 



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