April, '14] MELANDER: SPRAY RESISTANCE 167 



originally intended for a local experiment but is now an Adams project 

 under Doctor Hinds, Auburn, Ala., and this paper is presented with 

 his permission. 



Mr. W. E. Hinds: I wish to bring out one point which I think is of 

 interest. In the applications that have been made we found indica- 

 tions of a shedding due to the direct arsenical effects of the spray. 

 Some of the fruit that was shed from treated trees had certain char- 

 acteristics by which it could be distinguished from fruit shed from 

 untreated trees. The question has been brought up in connection 

 with these experiments as to the extent of this shedding due to arsenical 

 application. The percentage varies considerably when the neutral 

 and acid forms of arsenate of lead are" used. As far as I know this 

 point has not been considered heretofore. I would suggest at this 

 time to those who have arsenate spraying projects under way that 

 they see whether any way could be found to offset the shedding of 

 unpunctured fruit. 



Mr. W. M. Scott: Was there any difference noted as to the effect 

 of different forms of arsenate of lead on the foliage? 



Mr. W. E. Hinds: We had practically no injury. There were a 

 few burned areas but not enough to be of economic importance. 



President P. J. Parrott: Mr. A. L. Melander will present the 

 next paper entitled, "Can Insects become Immune to Spraying?" 



CAN INSECTS BECOME RESISTANT TO SPRAYS ?i 



By A. L. Melander, Entomologist, Washington Agricultural Experiment Station 



There is a prevalent feeling in some districts that sulphur-lime is 

 less efficient now than formerly in controlling San Jose scale, or orchard 

 aphides, or the brown mite. This has been largely ascribed to the 

 general adoption of the factory-made clear solution which is popularly 

 regarded as subject to a mysterious adulteration. 



There seems to be no question but that some years and in some 

 places sulphur-lime is a rapidly acting insecticide. In Piper's elab- 

 orate experiment at Wawawai, Washington, in 1902, he repeatedly 

 found all the scales dead a week after the application. The same is 

 true of some Wenatchee scales I examined two years ago. At the 

 same time that these Wenatchee scales were counted, specimens from 

 Clarkston, Washington, sprayed two weeks before, showed 90 per 

 cent alive. Even with 26° sulphur-lime, ten times stronger than a 

 normal application, 74 per cent of the scales were still alive. 



In the experiment of 1902 Piper discovered that sulphur-lime was 



1 Contribution from the Entomological Laboratory of the Bussey Institution, 

 Harvard University, No. 75. 



