Abstract
Glyphosate, the active ingredient of the most widely used commercial herbicide formulation, is extensively used and produced in China. Previous studies have reported sublethal effects of glyphosate on honeybees. However, the effects of commercially formulated glyphosate (CFG) at the recommended concentration (RC) on the chronic toxicity of honeybees, especially on their behaviours, remain unknown. In this study, a series of behavioural experiments were conducted to investigate the effects of CFG on honeybees. The results showed that there was a significant decline in water responsiveness at 1/2 × , 1 × and 2 × the RC after 3 h of exposure to CFG for 11 days. The CFG significantly reduced sucrose responsiveness at 1/2 × and 1 × the RC. In addition, CFG significantly affected olfactory learning ability at 1/2 × , 1 × , and 2 × the RC and negatively affected memory ability at 1/2 × and 1 × the RC. The climbing ability of honeybees also significantly decreased at 1/2 × , 1 × and 2 × the RC. Our findings indicated that, after they were chronically exposed to CFG at the RC, honeybees exhibited behavioural changes. These results provide a theoretical basis for regulating field applications of CFG, which is necessary for establishing an early warning and notification system and for protecting honeybees.
Highlights
Honeybees (Apis mellifera L.) are one of the most important economic insects for crop pollination
Previous studies have mostly used pure glyphosate (> 99%) in experiments to test the effect on h oneybees[17,18,19,20]; honeybees that are in direct contact with glyphosate in the field are commercially formulated glyphosate (CFG) at the recommended concentration (RC)
A significant decrease in the proboscis extension response percentage was detected in response to the 0.03% and 0.3% sucrose solutions after treatment with Roundup at 1/2 × the recommended concentration for 11 days
Summary
Honeybees (Apis mellifera L.) are one of the most important economic insects for crop pollination. In order to use pesticides safely, it is important to study the toxicity of commercial pesticide formulations to honeybees. Previous studies have mostly used pure glyphosate (> 99%) in experiments to test the effect on h oneybees[17,18,19,20]; honeybees that are in direct contact with glyphosate in the field are commercially formulated glyphosate (CFG) at the recommended concentration (RC). In China, honeybees may forage this herbicide at recommended concentration for a long time, but there are few studies on the adverse effects of honeybees under such conditions. Several studies demonstrated the influence of commercially formulated glyphosate to locomotion behaviors. There were few studies on the effects of the commercially formulated glyphosate at recommended concentrations on the abovementioned behaviors of honeybees
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