366 BOARD OF AGRICULTURE. [Pub. Doc. 



chemical reactions which lake place, arsenate of lead is 

 thrown down as a finely divided white precipitate which 

 readily remains suspended in water. This poison maybe 

 purchased in hulk in the market at about fifteen cents per 

 pound. Weight for weight it does not appear to be as 

 effective as either London purple or Paris green, but since 

 it will not burn the most delicate foliage when used at a 

 killing strength it Is pre-eminently the best insecticide of 

 the class. Notwithstanding the fact that the poison has not 

 proved all that was hoped for it when used against the 

 gypsy moth, — since a large proportion of the caterpillars 

 of this remarkably hardy insect have been known to feed 

 unharmed on foliage sprayed with great strengths of the 

 poison, — it has proved very effective against ordinary 

 insects and its use is to be highly recommended. It can be 

 safely applied to plants either clear or mixed with plaster, 

 middlings, ric, as in the case of Paris green, or used on 

 both plants and trees as a spray when mixed with water at 

 the rate of two to four pounds to one hundred and fifty 

 gallons. Twenty pounds to one hundred and fifty gallons 

 of water have been u>in\ in many experiments against the 

 gypsy moth without apparent injury to the foliage. Another 

 advantage of this poison is that it leaves a faint white coat- 

 ing on the foliage, thus indicating the places sprayed. I 

 have seen trees that were sprayed in June and yet showed 

 the coating plainly in August. 



The chief value of arsenate of lead, however, lies in its 

 insolubility in water, which obviates the danger of burning 



the foliage. This has always been the principal objection 



to the use of arsenicals, since foliage "burned" soon falls 

 to the ground, and a tree thus deprived of its Leaves in the 

 middle of a season is of course unable to ripen its fruit or 

 successfully complete the year's growth of wood, and, in 

 addition, is materially injured by the exhaustion of the 

 reserve force necessary to produce the second crop of Leaves 

 which most species of deciduous trees bring forth when 

 defoliated early in the season. Thus the damage to the tree 

 from "burning" is often as great as that from defolia- 

 tion by insects. The burning effeel of arsenical poisons 



