I. THE EFFECT OF LONDON PURPLE AND 



PARIS GREEN UPON PEACH 



FOLIAGE. 



The success which has attended the use of arsenical sprays in 

 combatting the curculio upon the cherry and plum, has led to its 

 trial upon peach trees. London purple appears to have been 

 most generally used in these trials, because this material has been 

 strongly recommended during the last few years as preferable to 

 Paris green. The advantages which London purple possesses 

 over Paris green are its cheapness, and the fineness and lightness 

 of the material, allowing it to remain longer in suspension in 

 water. But the use of London purple upon the peach has often 

 resulted in great injury to the foliage, and sometimes to the young 

 shoots. In fact, so serious were the injuries last year, particularly 

 in the peach region of Michigan, and so fully were they discussed 

 in the press, that there appears to have been very few trials of 

 spraying the peach during the present season. 



The injuries in the Michigan peach orchards last year led Pro- 

 fessor Cook to experiment upon the influence of the arsenites upon 

 foliage. He found (Bull. 53, Mich. Exp. Station) that "peach 

 foliage is especially susceptible to injury," that London purple 

 is more injurious to foliage than is Paris green, and that " this is 

 doubtless owing to the soluble arsenic which is quite abundant in 

 London purple and almost 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 oc- 

 curred 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 peach, it was concluded that 

 Paris green alone should be used, and that "not stronger than 

 one pound to three hundred 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 



