Spinosad-mediated effects on the walking abilities, midgut, and Malpighian tubules of Africanized honey bee workers

Abstract

The global decline in Apis mellifera colonies is attributed to multiple factors, including pesticides. The bioinsecticide spinosad was initially recognized as safe for non-target organisms; however, its toxicity has been changing this concept. Here, we investigated the survival, behavioral changes, and structural changes in the midgut and Malpighian tubules of A. mellifera treated orally with a spinosad formulation. The field-recommended concentration of spinosad killed 100% of the bees. The concentrations (LC5 and LC50) of spinosad altered the behavioral activity, reducing the walking distance and velocity, and increasing the resting time in comparison to control. The LC50 caused disorganization of the epithelia of tested organs and induced a perceived oxidative stress and cell death. The present work provides new insights into the debate about the role of bioinsecticides in the mortality of Africanized honey bees. Even at very low concentrations, the spinosad formulation is toxic for the vital organs midgut and Malpighian tubules and had adversely affected walking behavior. This detailed evaluation of the impact of the bioinsecticide on A. mellifera will contribute to the clarification of probable mediated disturbances caused by spinosad formulations, which can be used to develop more sustainable protocols in agriculture.