SOCIETY OF NORTHERN ILLINOIS. 317 



found in 1888 a pound of London Purple to a hundred gallons to 

 injure the foliage of some trees, and consequently determined to 

 use thereafter one pound to 200 only. The damage to plums and 

 peaches in Mr. Jabez Webster's orchard has already been men- 

 tioned under another head. Gillette's white arsenic solutions 

 left hardly a green leaf upon the plum when used of a strength of 

 one pound to 250 gallons, while one to four or five hundred badly 

 scorched the leaves, and one to 800 damaged them so severely as 

 to forbid the use of this insecticide. Three weeks after applica- 

 tion in another experiment, there was scarcely a green leaf left on 

 the plum when the strength exceeded one pound to 600 gallons. 

 Even one to 1200 took off about half the leaves and left the re- 

 mainder looking sickly and somewhat burned, and a pound to 

 1500 gallons damaged the leaves quite seriously. One pound to 

 200 not only destroyed every leaf but killed the small twigs also. 

 Cook, in 1888, sprayed plum trees with London Purple, one 

 pound to one hundred gallons, three times in succession during 

 the month of June, quite without injury to the foliage; but later, 

 as seen above, experience led him to abandon the use of London 

 Purple for this fruit. 



Cherry. The cherry is the hardiest of fruit trees with regard 

 to injury by the arsenites, and seems not to have been hurt at 

 all by a London Purple mixture of one pound to a hundred gal- 

 lons of water, used by Weed in 1888 in his elaborate experi- 

 ments ; and Cook had substantially the same experience in that 

 year. Sixteen cherry trees sprayed in May and June of 1889 

 were not at all injured, except one treated July 8th with one 



f>ound of London Purple to 200 gallons of water. Here the 

 eaves were only slightly damaged. On the other hand, eight 

 trees treated with a mixture of twice that strength, June 7th 

 and 12th, were not hurt at all. The injury noticed seems here 

 connected with the later date of use. 



Peach. The peach has thus far proved far the most sensitive 

 to arsenites of all our fruit trees, — so sensitive, in fact, as to 

 make it doubtful if these poisons can ever be used with any suc- 

 cess for this fruit. London Purple is certainly so caustic to the 

 leaves as to forbid its use under any circumstances. My own 

 experiments made last June, and reported in "Insect Life," 

 were not decisive, but had at least a temporary value. They 

 showed that one pound of London Purple to 100 gallons of 

 water was somewhat more injurious to the leaves than one to 

 200, but that both did considerable injury as the result of a 

 single spraying. Paris Green seemed somewhat less harmful, 

 corresponding mixtures of the poison causing a loss of no more 

 than five or six per cent, of the leaves. Cook applied poisons 

 to thirty-two peach trees in June and July, 1889, all the London 

 Purple mixtures, one pound to 100 gallons and one to 200 gal- 

 lons, doing great injury, as did also water poured off from Lon- 



