Evaluating exposure and potential effects on honeybee brood (Apis mellifera) development using glyphosate as an...

Area of Science:

• Ecotoxicology
• Apiculture Science
• Environmental Chemistry

Background:

• Assessing pesticide impact on honeybee brood is crucial for pollinator protection.
• Previous methods often lack realistic exposure scenarios.
• Worst-case exposure rates require accurate residue quantification.

Purpose of the Study:

• Develop and validate a two-stage approach to evaluate pesticide effects on honeybee brood.
• Establish realistic worst-case exposure rates for honeybee colonies.
• Quantify glyphosate residues in relevant matrices and assess its impact on brood.

Main Methods:

• Stage 1: Exposed honeybee colonies to glyphosate on Phacelia tanacetifolia, quantifying residues in pollen and nectar.
• Measured glyphosate levels in larvae.
• Stage 2: Determined glyphosate toxicity to larvae and pupae via direct feeding at realistic dose rates.
• Utilized fenoxycarb as a toxic reference.

Main Results:

• Glyphosate residues were higher in pollen than nectar and declined rapidly.
• No significant adverse effects of glyphosate on honeybee brood survival, development, or pupal weight were observed.
• Fenoxycarb caused significant brood mortality and population decline, serving as a positive control.
• Mean glyphosate residues in larvae correlated between field exposure and controlled dosing.

Conclusions:

• The developed approach realistically quantifies honeybee colony exposure to pesticides.
• It enables accurate dose-setting for higher-tier honeybee toxicity studies.
• This method is versatile for various pesticide properties and reduces the need for extensive field studies.