Acute toxicity of glyphosate to the Asian honey bee, Apis cerana: Evidence from topical and residue contact bioassays

Abstract

Glyphosate is the most widely used broad-spectrum herbicide worldwide, targeting the plant-specific shikimate pathway but increasingly scrutinized for its potential effects on non-target pollinators. Acute toxicity of Glyphosate 41 SL (Roundup) to the Asian honey bee, Apis cerana was evaluated through LC50 estimation using topical and residue contact bioassays. Topical application produced an LC50 value of 6989 ppm, with wide fiducial limits (4623.06 - 10202.70 ppm) indicating that only relatively high concentrations result in 50% mortality under direct exposure. Residue contact exposure yielded a slightly higher LC50 of 7932 ppm (fiducial limits: 4810.39-12810.17 ppm), reflecting reduced toxicity when bees encounter dried herbicide deposits rather than direct spray droplets. The difference between LC50 values for the two exposure routes highlights the influence of application mode on acute lethality. Overall, the LC50 estimates demonstrate low acute toxicity of Glyphosate 41 SL to A. cerana, while emphasizing the need to consider potential sublethal effects at lower, field-realistic concentrations.