Progress Report of Work of the Chemical Warfare Service on the Boll Weevil Anthonomus Grandis

Abstract

1. Preliminary tests have been made on some 1,000 poisons or poisonous mixtures, and of these about 50 have shown a toxicity equal to or greater than calcium arsenate. About 20 of these materials show little or no injury to the cotton plant. A total of over 100,000 weevils were used in the tests made. 2. Barium, lead, zinc, mercury, and to a less extent iron, have shown up in the tests as having some measure of toxicity to the boll weevil when combined with other chemical groups in themselves harmless, and the toxicity of these metals seems, in general, to be retained when combined with arsenic, and to increase the toxicity of the resulting arsenical. 3. Sodium fluosilicate, barium fluoride, and cryolite seem to be equally as effective as calcium arsenate on a volume for volume basis. Every effort should be made to decrease the specific gravities of these compounds so as to give them the same covering power as the calcium arsenate. 4.. It is believed that an advantage will be gained if the percentage of arsenic in calcium arsenate is reduced and a larger amount per acre used. 5. Arsenic trioxide or arsenic pentoxide, in relatively small percentages, absorbed on coal dust or some similar vehicle may make an effective economical poison against the boll weevil if some agent such as an oil be used to prevent plant burning. 6. The weevil seems to get most of the poison by more or less accidentally coming in contact with the dust particles and subsequently taking the same into its system. The weevil does obtain some poison through its food and drink. 7. High concentrations of toxic gases are ineffective against the weevil due to its apparent ability to suspend breathing more or less at will. There may still be a possibility that low concentrations of a persistent cumulative gas on adsorbents may give effective control. 8. The amount of arsenic in the best available form (soluble As2O3) necessary to poison a weevil is estimated as about 0.00015 mg. 9. The average weight of a boll weevil is 16 mg. The average quantity of water. drunk per day is roughly estimated as 0.0025 cc. (2.5 mg.), and the air breathed per weevil per hour is very roughly estimated as 0.46 cc. 10. The work has emphasized the necessity for the very careful management of dusting machinery so as to secure an even distribution of the poison over the plant. A calm, or a very low, wind is a necessity. The cotton plant should be moist, if calcium arsenate is used.