Improving the honey bee larval toxicity test
- This test can experience unacceptably high levels of control mortality making the test difficult to conduct reliably.
- Several different method improvement steps were evaluated and then tested.
- A ring test was completed with the cooperation of 15 laboratories located around the world using modifications developed by the University of Florida.
Results and Conclusions
- Problems with low control survival are solvable with the modifications tested.
- Performance of controls met quality criteria for 13 of 15 labs.
- Solvent controls performed poorer than water controls; performance depended on solvent concentration in diet. More work is needed to identify the best solvents that do not unacceptably affect the control survival and the outcome of the study.
- Tests with a reference toxicant (dimethoate) were consistent across laboratories. The NOEC and LD50 values across labs varied within a factor of 2.
- The honey bee chronic larval toxicity test, using modifications ring-tested by the PRTF, can be considered a reliable test method for the determination of potential effects of pesticides on honeybee larval development and emergence. Considering the ring-test data collected, the PRTF has encouraged the Organization for Economic Cooperation and Development (OECD) to update the OECD No. 239 “Guidance Document on Honey Bee Larval Toxicity Test following Repeated Exposure” to become a fully validated OECD Test Guideline.