Recent experiences with bumblebee (Bombus terrestris) semi-field tunnel testing following ICPPR Non-Apis 2016 and 2017 workshop recommendations to investigate the insecticide chlorantraniliprole

The study investigated the potential impact of the insecticide chlorantraniliprole (Coragen® brand) on the bumble bee (Bombus terrestris L.) under semi-field conditions in Phacelia tanacetifolia in Germany based on ringtest protocols from the ICPPR Non-Apis workshops (2016 and 2017). The P. tanacetifolia crop was grown in soil treated with the predicted 20-year plateau concentration of chlorantraniliprole in the top 20 cm of soil (equivalent to a predicted 20-year plateau concentration of 0.088 mg a.s./kg). Additionally, two chlorantraniliprole applications at 60 g a.s./ha were made in the chlorantraniliprole treatments (T1 and T2). In T1 both applications took place before P. tanacetifolia flowering at BBCH 51-55 and BBCH 55-59. In T2 one application was conducted before P. tanacetifolia flowering at BBCH 55-59 and one application during P. tanacetifolia flowering and during daily bee flight at BBCH 61-62. The application in the control (C) and reference item treatment (R) (400 g dimethoate a.s./ha) was carried out during full P. tanacetifolia flowering and bumble bee flight. The bumble bee colonies were exposed to the treated flowering P. tanacetifolia crop for 20 days in the tunnels and afterwards the colonies were kept on a monitoring site. The results of this study indicate no significant differences between the chlorantraniliprole treatment groups T1 and T2 and the control regarding all parameters assessed (i.e. mortality in the colonies and in the tunnels, flight activity at the hive entrance, hive weight development, condition of the colonies and production of young queens and males). Overall, no effects of chlorantraniliprole on bumble bee B. terrestris colonies including queen/male production, adult and larval survival and forager flight activity were found.