Toxicity of Organic Insecticides to Honeybees: Stomach Poison and Field Tests1

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Abstract
Honeybees were fed once with an emulsion of insecticide, placed in constant temp. cabinets and observed for 3 days. At 94[degree]F the M.L.D.''s for gamma benzene hexachloride, chlordane and toxaphene were, respectively, 0.001296, 0.01249 and 0.27778 mg. insecticide/g. body wt. At 94[degree] F sufficient concns. of DDT to produce mortality could not be attained by the method employed, but at less than 82[degree]F the M.L.D. was 0.2913 mg. DDT/g. body wt. Varying dosages of insecticides were dusted on cotton growing in screen cages 6 x 6 x 36 ft., and small colonies of bees allowed to work inside the cages. Dead bees were collected daily and percentages of mortality calculated. In 8 applications of a total of 130 lbs. of 10% chlordane 25% of the bees were killed, 10% DDT killed 9%, while 20% toxaphene and 3% gamma benzene hexachloride-5% DDT killed less than 3% of the bees. The BHC-DDT mixture was repellent for about 3 hours following applications. Ca arsenat was highly toxic and preliminary expts. indicated that parathion was more toxic than other organic insecticides. Field observations on DDT, BHC, toxaphene and Ca arsenate indicated that the cage tests were reliable. Bees appear to gather little cotton pollen. Observations on the secretion of nectar by cotton are descr.

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