Chlorantraniliprole: Lack of effects on bumblebee reproduction (Bombus terrestris) under semi-field conditions in Phacelia tanacetifolia

Background: In a semi-field trial the effect of chlorantraniliprole spray application on Phacelia tanacetifolia on the bumblebee, Bombus terrestris L. (Hymenoptera, Apidae), was studied.
Results: Chlorantraniliprole applied twice at 60 g a.s./ha as a spray application on flowering Phacelia with a 9-day spray interval during daily bumblebee flight did not have any pertinent effects regarding all parameters assessed, i.e. mortality, flight activity, hive weight, condition of colonies, development of bumblebee brood, production of young queen offspring and vigor relative to the water treated control. Similar numbers of young queens and drones were determined in the chlorantraniliprole and control treatments. No residues above the level of quantification (LOQ) of 0.001 mg/kg were found in any of the control samples in pollen or nectar. Residues of chlorantraniliprole above the LOQ level were found for all matrices after application in the chlorantraniliprole treatment. Residues in pollen samples were generally higher compared to the nectar samples, while chlorantraniliprole residue levels declined rapidly in both matrices after each spray application.
Conclusion: In a semi-field trial no effects of chlorantraniliprole applied twice at 60 g a.s./ha on the bumblebee, Bombus terrestris, including reproduction was found.