56 MASS. EXPERIMENT STATION BULLETIN 184. 



centage of efficiency will depend mainly upon thoroughness of applica- 

 tion. 



6. The ordinary dormant-season treatment of apple orchards with 

 miscible oil against San Jose scale, if applied thoroughly at the delayed 

 dormant period, should result in practically a perfect control of apple 

 aphids also. 



7. Delayed dormant apphcations of full dormant-season strength lime- 

 sulfur, lime-sulfur and nicotine sulfate combined, and miscible oils, if 

 perfect, can be made without material injury to apple foliage. Even 

 when the foliage is considerably more advanced, little severe injury 

 usually results. This fact, if taken into account, might make unnecessary 

 separate applications 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-sulfur in destroying both the aphid eggs and 

 living insects appears to be mainly mechanical, by sticking them to the 

 twigs. 



9. The action of nicotine sulfate in killing the hving aphids is slow, 

 requiring from about half an hour to twenty-four hours or more for different 

 individuals. Death appears to be due to paralysis. 



10. Miscible oils are practically instantaneous 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 Massachu- 

 setts Agricultural Experiment Station staff for assistance in carrying out 

 the insecticide tests, and to Dr. H. T. Fernald for his kind suggestions 

 and assistance. 



Bibliography. 



1908. Gillette, C. P., and Taylor, E. P. "Orchard Plant Lice and Their Reme- 

 dies." Bulletin 134, Colorado Agricultural Experiment Station. 



1910. Wallace, E. "Spray Injury Induced by Lime-sulfur Preparations." Bul- 



letin 288, Cornell University Agricultural Experiment Station. 



1911. Shafer, G. D. "How Contact Insecticides Kill." Technical Bulletin 11, 



Michigan Agricultural Experiment Station. 



1914. Tartar, H. V. "On the Valuation of Lime-sulfur as an Insecticide." Journal 



of Economic Entomology, Vol. VII., p. 463. 



1915. Parrott, P. J., and Hodgkiss, H. E. "The Status of Spraying Practices for 



the Control of Plant Lice in Apple Orchards." Bulletin 402, New York 

 Agricultural Experiment Station, Geneva, N. Y. 



1915. Shafer, G. D. "How Contact Insecticides Kill." Technical Bulletin 21, 



Michigan Agricultural Experiment Station. 



1916. Mclndoo, N. E. "Effects of Nicotine as an Insecticide." Journal of Agri- 



cultural Research, Vol. VII., No. 3, p. 89, United States Department of 

 Agriculture. 



