Chemical Warfare against the Boll Weevil. H. W.
WALKER (Chemical Warfare, I927, I3,(231)(232)(233)(234)(235)(236)(237) describes the work of the Chemical Warfare Service, United States Army on experiments in exterminating the cotton boll weevil. An extensive study was made, using over IOOO poisons and poisonous mixtures. Two materials were developed at Edgewood Arsenal and found to be commercially possible boll weevil poisons, a special calcium arsenate and a special sodium fluosilicate. The special calcium arsenate contains 20 per cent. arsenic anhydride, and is made by heating calcium carbonate (precipitated chalk) and arsenious oxide (white arsenic) in the presence of an excess of air at a temperature of 65 ยฐ0 C. The special sodium fluosilicate is a byproduct in the manufacture of acid phosphate, and contains approximately 80 per cent. sodium fluosilicate and 20 per cent. colloidal silica. Both insecticides have a toxicity for the cotton boll weevil at least equal to that of commercial calcium arsenate, and do not burn or damage the cotton plant. Barium fluosilicate is an excellent insecticide .for this purpose, but does not possess sufficiently increased toxicity to replace the other less expensive compounds. The special sodium fluosilicate acts on the weevil more rapidly than does the special calcium arsenate, but, at the present stage of development of the process of manufacture, does not stick to the cotton plant so readily. These insecticides have been used as dusts, but possibly may be applied as syrups.
J.S.H.