Neonicotinoid

Neonicotinoid use has been linked in a range of studies to adverse ecological effects, including honey-bee colony collapse disorder (CCD) and loss of birds due to a reduction in insect populations. Some scientific findings regarding the harm caused to bees by neonics have been conflicting and controversial. This is partly because bees exposed to normal levels of neonicotinoids do not immediately die. Some sources have proposed that neonicotinoids reduce a bee colony's ability to survive the winter. Most academic and governmental bodies agree that neonicotinoids have had a negative influence on bee populations. In 2013, the European Union and a few neighbouring countries restricted the use of certain neonicotinoids; in 2018, the EU banned the three main neonicotinoids (clothianidin, imidacloprid and thiamethoxam) for all outdoor uses. Several states in the United States have also restricted usage of neonicotinoids out of concern for pollinators and bees. The precursor to nithiazine was first synthesized by Henry Feuer, a chemist at Purdue University, in 1970; Shell researchers found in screening that this precursor showed insecticide potential and refined it to develop nithiazine. In 1984 nithiazine's mode of action was found to be as a postsynaptic acetylcholine receptor agonist, the same as nicotine. Nithiazine does not act as an acetylcholinesterase inhibitor, in contrast to the organophosphate and carbamate insecticides. While nithiazine has the desired specificity (i.e. low mammalian toxicity), it is not photostable—that is, it breaks down in sunlight, thus is not commercially viable. In 1985, Bayer patented imidacloprid as the first commercial neonicotinoid. During the late 1990s, primarily, imidacloprid became widely used. Beginning in the early 2000s, two other neonicotinoids, clothianidin and thiamethoxam, entered the market. As of 2013, virtually all corn planted in the United States was treated with one of these two insecticides. As of 2014, about a third of US soybean acreage was planted with neonicotinoid-treated seeds, usually imidacloprid or thiamethoxam. Neonicotinoids have been registered in more than 120 countries. With a global turnover of €1.5 billion in 2008, they represented 24% of the global market for insecticides. After the introduction of the first neonicotinoids in the 1990s, this market has grown from €155 million in 1990 to €957 million in 2008. Neonicotinoids made up 80% of all seed treatment sales in 2008. As of 2011, seven neonicotinoids from different companies are on the market. Imidacloprid is effective against sucking insects, some chewing insects, soil insects and fleas on domestic animals. It is systemic with particular efficacy against sucking insects and has a long residual activity. Imidacloprid can be added to the water used to irrigate plants. Controlled release formulations of imidacloprid take 2–10 days to release 50% of imidacloprid in water.It is applied against soil pests, seed, timber and animal pests as well as foliar treatments.