The effect of insecticides, flupyradifurone and sulfoxaflor on Osmia lignaria survival and enzyme expression

The blue orchard bee (Osmia lignaria) is a native North American bee species and an effective pollinator of fruit and tree nut crops. Currently, O. lignaria is used to supplement honey bee pollination of almonds in California and sweet cherries in New England. It can be more sensitive to certain pesticides, however, when compared to honey bees and bumble bees. To ensure the continued pollination service of these native bees, it is important to assess the impact of pesticides on their health and to research some of their potential methods of detoxification. Two novel insecticides that bees can encounter in the field are sulfoxaflor and flupyradifurone. They have a similar mode-of-action to neonicotinoids, acting on the nervous systems of insects. In this study, we orally exposed O. lignaria adult males and females to field realistic doses of sulfoxaflor and flupyradifurone. For one exposed group, we measured their survival over 4 days following exposure. For the other, we dissected out the bee heads, thoraxes, and bee midguts at 24 and 48 hours after exposure and used them to measure the expression of bee detoxification enzymes (glutathione-S-transferases, esterases, and cytochrome p450 monooxygenases). We compared enzyme expression and survival in male and female O. lignaria. Female O. lignaria had high mortality compared to males and compared to similar studies in social bees. Results of the enzyme expression analysis will be discussed.