Testing effects of field realistic pesticide tank mixtures used in organic orchard farming on adult honey bees and bee colonies

In Germany, tank mixtures consisting of several insecticides do not comply with good agricultural practice, even if the individual mixing partners are classified as not dangerous to bees. These mixtures are considered as harmful to bees and should therefore not be used on plants which are in flower or which are visited by bees as a precautionary measure. Therefore, this project aimed to investigate if tank mixtures of insecticides used in organic orchard farming actually affect honey bees under realistic field exposure scenarios. Accordingly, different insecticide mixtures were tested in the laboratory and under semi-field conditions to evaluate their risk for honey bees. Tested insecticides included tank mixtures of the products Neudosan NEU (fatty acid potassium salt 515 g/L) and Micula (rapeseed oil 785.75 g/L), Neudosan NEU and Netzschwefel Stulln (sulphur 796 g/kg), Neudosan NEU and Kumulus WG (sulphur 800 g/kg) as well as the tank mixture of Kumar (potassium hydrogen carbonate 850 g/kg) and Netzschwefel Stulln. The first level of testing considered a contact exposure of honey bees to a spray solution at field realistic exposure rates in the laboratory using a spray chamber. In case of biologically relevant effects at the laboratory level, additional tests were conducted under semi-field conditions with whole bee colonies. The results obtained for all tested tank mixtures did not indicate an increased risk for honey bees and honey bee colonies when exposed up to the maximum authorized field realistic application rates.