Imidacloprid: Impact on Africanized Apis mellifera L. (Hymenoptera: Apidae) workers and honey contamination.

Apis mellifera L. (Hymenoptera: Apidae) is fundamental in the production chain, ensuring food diversity through the ecosystem service of pollination. The aim of this work was to evaluate the impact of imidacloprid, orally, topically, and by contact, on A. mellifera workers and to verify the presence of this active ingredient in honey. Toxicity levels were verified by bioassays. In bioassay 1, the levels correspond to the percentages of 100, 10, 1, 0.1, and 0.01% of the recommended concentration for field application of the commercial product Nortox® (active ingredient imidacloprid), with which we obtained the mean lethal concentration (LC50) in 48 h for A. mellifera, determining the concentration ranges to be used in the subsequent bioassays. Bioassays 2 and 3 followed the guidelines of the Organization for Economic Cooperation and Development, which specify the LC50 (48 h). In bioassay 4, the LC50 (48 h) and the survival rate of bees for a period of 120 h were determined by contact with a surface contaminated with imidacloprid, and in bioassay 5, the interference of the insecticide with the flight behavior of bees was evaluated. Honey samples were collected in agroecological and conventional georeferenced apiaries and traces of the imidacloprid were detected by means of high-performance liquid chromatography (HPLC-UV) with extraction by SPE C18. Bee survival was directly affected by the concentration and exposure time, as well behavioral performance, demonstrating the residual effect of imidacloprid on A. mellifera workers. Honey samples from a conventional apiary showed detection above the maximum residue limits (MRL) allowed by the European Union (0.05 µg mL-1), but samples from other apiaries showed no traces of this insecticide. Imidacloprid affects the survival rate and behavior of Africanized A. mellifera and honey quality.

Possible interference of Bacillus thuringiensis in the survival and behavior of Africanized honey bees (Apis mellifera).

Bacillus thuringiensis (Bt), an entomopathogenic bacterium, has been used as bioinsecticides for insect pest control worldwide. Consequently, the objective of this work was to evaluate the possible effects of commercial formulations of Bt products, Dipel and Xentari, on the survival and behavior of Africanized honey bees (Apis mellifera). Bioassays were performed on foragers and newly emerged (24-h-old) bees that received the products mixed in the food. Their survival and behavior were evaluated through the vertical displacement tests and the walk test, analyzed using software Bee-Move. Then, histological analysis of the mesenterium was performed. As control treatment was used sterile water. The honey bees' survival was evaluated for between 1 and 144 h. No interference of B. thuringiensis, Dipel and Xentari, in the survival of Africanized honey bees were found. Only Xentari interfered with vertical displacement behavior of newly emerged (24-h-old) bees. Both the products tested were selective and safe for A. mellifera.