Neonicotinoid Insecticides: Chemistry, Mode of Action, Uses, Environmental Fate and Ecological Consequences
Neonicotinoids are systemic, nicotine-derived insecticides that act primarily as agonists of insect nicotinic acetylcholine receptors. Their selective activity against insect pests, broad-spectrum efficacy and versatility in seed, soil, foliar and trunk-injection applications have supported extensive use in agriculture, veterinary ectoparasite control and structural pest management. This review examines their chemistry and structural classification, mode of action, field applications, physicochemical behaviour, environmental fate, ecological consequences and available remediation approaches. The properties that support systemic movement, particularly high water solubility, relatively low soil sorption and persistence, also promote movement from treated sites into soil, groundwater, surface water and plant tissues. Evidence summarised in the manuscript indicates risks to non-target organisms, including pollinators, aquatic invertebrates, earthworms and birds, together with the potential for dietary and environmental exposure in mammals. Residue persistence varies markedly among compounds, soil conditions, plant species and methods of application, while repeated use can extend environmental exposure. Current remediation approaches include physicochemical treatment, microbial remediation and phytoremediation, although each has practical limitations related to cost, efficiency, treatment duration or secondary impacts. Overall, the reviewed evidence indicates that effective neonicotinoid pest management requires careful regulation, judicious application and integration with preventive and ecologically compatible pest-management strategies to reduce off-target contamination while retaining necessary crop-protection benefits.