Effect on Honey Bees of Nectar from Systemic Insecticide-Treated Plants1

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Abstract
Foliage and soil applications of systemic insecticides were tested for their effect on honey bees, A pis mellifera L., through nectar contamination in 3 species of flowering plants. Nectar from plants sprayed with 0.1% dimethoate and 0.8% phosphamidon was toxic to honey bees for at least 2 to 3 days. Soil application of 4 lb actual dimethoate per acre and 32 lb actual phosphamidon also created toxic nectar for 3 days or more. Phorate, tested only as a spray (0.1 to 0.8%), did not create Toxicity in nectar during a 3-day test. Bees foraging on blooming alfalfa were killed up to 5 days after an evening application of 1 lb dimethoate per acre. Phosphamidon does not appear to be hazardous at recommended field dosages but dimethoate should not be applied to flowering crops attractive to bees. Granular applications created less nectar toxicity than sprays at equal amounts of active ingredient per acre.