Effects of tank mixtures of plant protection products on honey bees and possible physiological interactions

Abstract

During foraging bouts pollinators like honey bees may be exposed to multiple plant protection products (PPPs). In contrast to applications of single PPPs the effects of tank mixtures are not routinely evaluated in the risk assessment process of PPPs with the exception of known synergistic insecticides and mixing partners. Due to economical constraints and process efficiency PPP mixtures are commonly used in agricultural practices. However, sometimes interactions among agrochemicals lead to undesirable additive and synergistic effects. Especially mixtures of pyrethroids or neonicotinoids with azole fungicides, which inhibit sterol biosynthesis, have a synergistic poten­tial of negatively affecting honey bees. For such mixtures, regulatory restrictions are already in place. These synergistic effects are associated with azole fungicides inhibiting the main detoxification enzyme P450, which hinders the bee to detoxify the insecticide. Further studies provide first evidence for increased impacts of mixtures of insecticides with adjuvants on honey bees. More research is necessary to better understand mixture toxicity and to implement this knowledge in the risk assess­ment.