244 



fulstmly, from which lessons of practical value may be learned, but it must not be 

 forgotten that as yet this important investigation is but fairly begun, and it may 

 prove that conclusions hastily deduced from even the great mass of data already 

 secured will require, as the investigation shall progress, very serious modifications. 

 In the next bulletin there will begin a record of the milli product of the herd and 

 investigations of its quality for the several purposes of the dairy. 



New York Cornell Station, Bulletin No. 18, July, 1890 (pp. 15). 



EXPEEIENCES IN SPRAYING PLANTS, L. H. BAILEY, M. S. (pp. 29- 



41, illustrated). 



The effect of London purple and Paris green upon peach foliage. — Lon- 

 don purple has of late been much used on peach trees as an insecticide 

 on account of its cheapness and its fineness and lightness, which allow 

 it to remain longer in suspension in water. But so many complaints 

 have been made that this arsenite is injurious to the foliage and some- 

 times to the young shoots that experiments have been instituted with 

 reference to the influence of the arsenites on foliage. As the result of 

 such experiments at the Michigan Station last year,* Professor Cook 

 considers that — 



"Peach foliage is especially susceptible to injury," that London purple is more in- 

 jurious to foliage than is Paris green, and that "this is doubtless owing to the solu- 

 ble arsenic which is quite abundant in London purple and altpost absent in Paris 

 green." The colored liquid left after the complete settling of the London purple was 

 destructive to peach foliage. It appeared that greater injury occurred when the 

 spraying was performed shortly before a rain, and that "spraying soon after the 

 foliage puts out is less harmful than when it is delayed a few days, or better a few 

 weeks." As a general result of the trials upon the i>each, it was concluded that Paris 

 green alone should be used, and that " not stronger than 1 pound to 300 gallons of 

 water." 



In this condition the matter rests. We still need to know if the above conclusions 

 are applicable to other regions and other years; what are the chemical histories of 

 these arsenites; why and how it is that the poisons injure the peach; if injury is 

 greater at certain seasons of growth ; if the time of day, meteorological conditions, 

 methods of application, and other minor conditions influence the results. It has been 

 supposed by many that the unusual meteorological conditions of last year were largely 

 responsible for the injuries. We performed experiments looking in these directions 

 last year, but desired the experience of a second season to test the subject more fully. 

 We now find that the experiences of the two seasons coincide, so far as the experi- 

 ments are comparable. 



In seven experiments reported in this bulletin Paris green and Lon- 

 don purple in mixtures of 1 pound of the arsenite to from 200 to 400 

 gallons of water, were sprayed on peach trees at difl'ereut times from 

 May 21 to July 8. In the earliest experiment the London purple did 

 slight injury to the foliage, but in the other cases it proved very in- 

 jurious, in some instances injuring the young shoots as well as the 

 leaves. The injury done by the Paris green was slight. In another 

 experiment a tree was sprayed with London purple, which was imme- 



*Michigan Station, Bulletin No. 53 ; Experiment Station Kecord, Vol. I, p. 227. 



