ENTOMOLOGICAL DEPARTMENT. 319 



abundant in London purple, and almost absent in Paris green. In experi- 

 ment No. 29 (See table) it will be noticed that the colored water after Lon- 

 don purple fully settles is very destructive to foliage, while analine (See 

 experiment No. 32) is not at all harmful. This agrees with the experiments 

 of Prof. C. P. Gillette, made in 1888, where white arsenic was found very 

 destructive to foliage. 



Secondly, Peach foliage is especially susceptible to injury, and cherry 

 foliage the least so of any of the kinds treated. 



Thirdly, It would seem that London purple and white arsenic, used just 

 before a rain, are more harmful than when used during a drought. We not 

 only^aw greater injury when a rain followed spraying within two or three 

 days, but secured the same results by spraying, soon after treatment, with 

 pure water. This also accords with the view that the injury comes from 

 the presence of soluble arsenic. 



Fourthly, It would seem that spraying soon aftor the foliage puts out is 

 less harmful than when it is delayed a few days, or better, a few weeks. For 

 ten years I have sprayed both apple and plum trees in May, and for several 

 years with London purple, and often used a mixture as strong as one pound 

 to one hundred, or even fifty gallons of water. Yet in most cases no dam- 

 age was done. This year I sprayed several trees in May, using one pound 

 to 100 gallons of water with no damage. In June and July spraying the 

 same trees with a mixture only one-half as strong did no slight injury. This 

 fact, if fact it be, accounts for the few reports of injury in the past, even 

 with a stronger mixture, and the frequent reports of damage within a year 

 or two, even with a dilute mixture. Then the spraying was confined to 

 May ; now it reaches to June, or even to July. 



Fifthly, London purple may be used on apple, plum, cherry, pear, and 

 most ornamental trees, but on these should never be stronger than one 

 pound to two hundred gallons of water. If the application is to be repeated, 

 as it must be for the curculio, to prove effective, or if it is to be used in 

 June or July, Paris green should be used, in the same proportion as above, 

 or else we should only use one pound of London purple to three hundred 

 gallons of water. I now think that this necessity is more due to time of 

 application than to the fact of increased quantity of the poison. 



Sixthly, If the arsenites are to be used on the peach, to defend against 

 the curculio, Paris green only should be used, and that not stronger than 

 one pound to three hundred gallons of water. With the peach the poison 

 is not only absorbed, coloring the tissue purple or brown, but even the 

 petiole or stem of the leaf is weakened, and the leaf falls. Thus in several 

 cases where we used London purple, one pound to two hundred gallons of 

 water, or white arsenic, the peach leaves all fell off. White arsenic colors 

 the tissue the same as does the London purple, showing once more that it 

 is the soluble arsenic, not analine, that does the mischief. 



Seventhly, The injury done to the foliage is never immediately apparent. 

 It usually shows somewhat the second day, but the full injury is frequently 

 not manifest till the fifth day, and often not till the tenth. 



POISONING THE PASTURE UNDER THE TREES. 



Another important practical question which I have tried to settle this 

 season — 1889 — concerns the danger of pasturing under trees which have 

 been sprayed with the arsenites. 



