Time-to-death approach to reveal chronic and cumulative toxicity of a fungicide for honeybees not revealed with the standard ten-day test
Year: 2018
Type: article
Abstract: Synthetic fungicides are pesticides widely used in agriculture to control phytopathogenic fungi. The systemicity, persistency and intense application of some of these fungicides, such as boscalid, leads to long periods of exposure for honeybees via contaminated water, pollen and nectar. We exposed adult honeybees in the lab to food contaminated with boscalid for 33 days instead of the standard 10-day test. Most of the toxic effects were observed after 10 days. The median time to death (LT 50 ) ranged from 24.9 days (lowest concentration) to 7.1 days (highest concentration) and was significantly shorter in all cases than with the control (32.0 days). The concentration and dietary doses of boscalid inducing 50% mortality (LC 50 and LDD 50 , respectively) decreased strongly with the time of exposure: LC 50 = 14,729 and 1,174 mg/l and LDD 50 = 0.318 and 0.0301 mg bee −1 day −1 at days 8 and 25, respectively. We found evidence of reinforced toxicity when exposure is prolonged, but with an unusual pattern: no cumulative toxicity is observed until 17–18 days, when a point of inflexion appears that suggests a reduced capacity of bees to deal with the toxicant. Our results show the importance of time-to-death experiments rather than fixed-duration studies for evaluating chronic toxicity.
Source: Scientific Reports
Institutions: UCLouvain, Walloon Agricultural Research Centre
Language: English
Subfield: Insect Science
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,690
Funder: Waalse Gewest
OpenAlex ID: W2807678343