Understanding the frequency of non-additive effects (synergism and antagonism) is important in the context of risk assessment of pesticides. The goal of this study was to investigate the prevalence of non-additive effects of pesticides to honey bees (Apis mellifera). We investigated a large set of mixtures of insecticides and fungicides of different chemical modes of action and classes. We investigated whether the experimental toxicity of the mixtures could be reasonably predicted based on the Concentration Addition (CA) model for acute contact and oral adult bee toxicity tests. We measured the degree of the experimental toxicity from the predictions based on the well-known Mixture Deviation Ratio (MDR). Further, we investigated the MDR threshold/s that should be used for the identification of non-additive effects based on the typical experimental variability of the tests. We found that a deviation factor of 5 from the additivity predictions (MDR = 5) is a sound reference for labeling potential non-additive effects in acute adult bee experimental designs when assuming a typical Coefficient of Variation (CV%) = 100 when determining the LD50 of a pesticide (a factor of 2x deviation in the LD 50 ). We found that a 2.4% and a 9% of the mixtures presented an MDR &gt; 5 (potential synergy) and MDR &lt; 0.2 (potential antagonism), respectively. The frequency and magnitude of deviation from additivity found in this study for honey bees are consistent with those of other terrestrial and aquatic taxa found in previous studies. The mixtures included in this study represent a relevant sample of pesticides that are currently used in agricultural operations globally. Our findings suggest that synergy of pesticide mixtures to honey bees is rare and is not random but have mechanistic basis

How frequent is synergy to honey bees among pesticide combinations typically used in agricultural operations?

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.