The utility of immature honey bee toxicity bioassays for assessing mortality and sublethal effects from pesticide exposure

Honey bees in their immature stages may be exposed to pesticides during their development, leading to mortality and developmental abnormalities. To ensure pesticide safety, global regulations require toxicity tests with honey bees in different developmental stages. Currently, these tests are conducted using two standardized protocols by the OECD to assess acute (single-day) and chronic (multiple-day) exposure to larvae, which mainly comprises mortality assessments, even though growth and development may also be qualitatively evaluated. Considering the available standardized protocols, the goals of this study were to determine whether chronic toxicity tests on immature honey bees consistently result in a higher toxicity measurement than the acute single-day exposure tests, and whether the adult weight at emergence would be a good predictor of growth and development effects and a more sensitive indicator of pesticide effects on honey bee larvae than mortality alone. From the comparison of acute and chronic toxicity data for 43 pesticides on immature bees, information on acute toxicity can be derived from the chronic honey bee larvae test, and therefore negating the need for two separate larval toxicity tests. Furthermore, the analysis of survival and adult emergence weight from 46 chronic toxicity studies concluded that the weight of the adult bee after emergence was identified as the most sensitive indicator of pesticide effects in 22% of the studies. Further effort is needed to establish a standardized method for measuring the weight of emerged adults, thereby ensuring consistent procedures across testing laboratories.