Use of neonicotinoids and monitoring of its residues in honeybees and honeybee products

Abstract

The use of pesticides in agricultural cropping systems is often associated with mass extinction or population declines in honeybee colonies due to poisoning. Over the past 20 years, neonicotinoid pesticides have become the most widely used class of insecticides due to their high toxicity for insects but low toxicity to vertebrates, and high efficacy and systemic activity in plants. The basic structure consists of either a nitromethylene, nitroimine, or cyanoimine functional group, while their prime member is imidacloprid, the second most used pesticide in the world after glyphosate. By mode of action, neonicotinoids are considered agonists on the postsynaptic nicotinic acetylcholine receptor of the insect`s central nervous system, causing a blockage of signal transmission, resulting in disorientation, paralysis or even death. Residues of neonicotinoids can be present in plant pollen and nectar, the main natural food source that honeybees collect and store in hives. Numerous studies have demonstrated that concentrations of these insecticides have a negative effect on honeybee health and behaviour. In response to this concern, these substances have been subject to a peer review of the pesticide risk assessment, resulting in the prohibition by the European Commission of the use of clothianidin, imidacloprid, thiamethoxam and thiacloprid for all outdoor uses in Member States, with the exception of greenhouses. This review paper provides insight into the main properties of neonicotinoids, the development and implementation of reliable analytical methods for determination of their residues in honeybees and bee products, and the challenges faced due to the complex matrices that contain beeswax, proteins and other interfering compounds.