February, '10] GILLETTE : SULFID OF ARSENIC 31 



purpose as the arsenate of lead, which has, in the past few years, 

 ahnost completely taken the place of other poisons for the control of 

 the codling moth and other leaf-eating insects. 



Three other sprays, viz., lime, Black Leaf Extract, and Sulfate of 

 Nicotine, were also tested in hopes that they might prove benefieial. 

 As with the arsenical sprays, each was used but once, as the petals 

 were nearly all off. 



Good lump lime, 50 pounds to 100 gallons of water, seemed to give 

 no protection at all, as the percentage of perfect fruit on these trees 

 averaged 58.9, exactly as in case of the check trees. 



Black Leaf Extract was used in the proportion of 1 gallon diluted 

 to 50 gallons with water. The trees sprayed with this mixture gave 

 fruit that was 77 per cent free from worm injuries, or about 18 per 

 cent more perfect fruit than in the check block. 



Sulfate of Nicotine was used in the porportion of 1 part in 750 

 parts of water and seemed to give slight protection, as the trees 

 sprayed with this mixture bore fruit that was 73 per cent free from 

 all worm injuries, an improvement of practically 14 per cent over the 

 fruit of unsprayed trees. Even this application indicates a protection 

 of almost exactly 33 per cent of the fruit that would have been wormy 

 if untreated, for the check trees had but 41.1 per cent of their fruit 

 injured by worms. 



While I would not feel warranted from this year's experiments in 

 holding out very strong hopes that the codling moth can be sufficiently 

 controlled by the use of nicotine sprays, I am encouraged to continue 

 the experiment through another year and shall probably extend the 

 number of applications to three or four. One or two summer sprays 

 with either of these tobacco preparations will usually pay for them- 

 selves in their destruction of plant lice, red spiders and brown mites. 

 And then, if these nicotine sprays will enable us to get fairly good 

 protection from the injuries of the codling moth, it will be a boon to 

 those whose orchards are already sick and dying from the excessive 

 use of arsenical mixtures. 



My chief hope, however, for relief from the overaccumulation of 

 arsenic in our soils in a form that is detrimental to the growth of 

 vegetation, lies in the use of the very insoluble sulfide of arsenic. This 

 compound also has the important advantage of being very much 

 cheaper than arsenate of lead, and if we can use it in solution it will 

 do away with the use of stirrers in the spray tanks, which will be 

 another decided advantage. 



I have also used this poison successfully, as an arsenic-bran mash, 

 for the destruction of grasshoppers, and as a spray for the destruction 



