Imidacloprid

Imidacloprid is a systemic insecticide belonging to a class of chemicals called the neonicotinoids which act on the central nervous system of insects. The chemical works by interfering with the transmission of stimuli in the insect nervous system. Specifically, it causes a blockage of the nicotinergic neuronal pathway. By blocking nicotinic acetylcholine receptors, imidacloprid prevents acetylcholine from transmitting impulses between nerves, resulting in the insect's paralysis and eventual death. It is effective on contact and via stomach action. Because imidacloprid binds much more strongly to insect neuron receptors than to mammal neuron receptors, this insecticide is more toxic to insects than to mammals.

From 1999 through at least 2018^[update], imidacloprid was the most widely used insecticide in the world. Although it is now off patent, the primary manufacturer of this chemical is Bayer CropScience (part of Bayer AG). It is sold under many names for many uses; it can be applied by soil injection, tree injection, application to the skin of the plant, broadcast foliar, or ground application as a granular or liquid formulation, or as a pesticide-coated seed treatment. Imidacloprid is widely used for pest control in agriculture. Other uses include application to foundations to prevent termite damage, pest control for gardens and turf, treatment of domestic pets to control fleas, protection of trees from boring insects, and in preservative treatment of some types of lumber products.

A 2018 review by the European Food Safety Authority (EFSA) concluded that most uses of neonicotinoid pesticides such as Imidacloprid represent a risk to wild bees and honeybees. In 2022 the United States Environmental Protection Agency (EPA) concluded that Imidacloprid is likely to adversely affect 79 percent of federally listed endangered or threatened species and 83 percent of critical habitats. The pesticide has been banned for all outdoor use in the entire European Union since 2018, but has a partial approval in the United States and some other countries. It still remains in widespread use in other major parts of the world.

Imidacloprid is one of the most widely used insecticides in the world. Its major uses include:

When used on plants, imidacloprid, which is systemic, is slowly taken up by plant roots and slowly translocated up the plant via xylem tissue.

When used on trees, it can take 30–60 days to reach the top (depending on the size and height) and enter the leaves in high enough quantities to be effective. Imidacloprid can be found in the trunk, the branches, the twigs, the leaves, the leaflets, and the seeds. Many trees are wind pollinated. But others such as fruit trees, linden, catalpa, and black locust trees are bee and wind pollinated and imidacloprid would likely be found in the flowers in small quantities. Higher doses must be used to control boring insects than other types.

The estimated annual use of the compound in US agriculture is mapped by the US Geological Service and shows an increasing trend from its introduction in 1994 to 2014 when it reached 2,000,000 pounds (910,000 kg). However, use from 2015 to 2019 dropped following concerns about the effect of neonicotinoid chemicals on pollinating insects. In May 2019, the Environmental Protection Agency revoked approval for a number of products containing imidacloprid as part of a legal settlement, although some formulations continue to be available.

On January 21, 1986, a patent was filed and granted on May 3, 1988, for imidacloprid in the United States (U.S. Pat. No. 4,742,060) by Nihon Tokushu Noyaku Seizo K.K. of Tokyo, Japan.