Neonicotinoids are active substances that are in the most widely used insecticides in the world. These active substances can kill insects when taken orally at very low concentrations. These have a chemical structure similar to nicotine. They are water-soluble and can be taken up by plants through the roots and transported to all parts of the plant, including pollen and nectar. Neonicotinoids damage the central nervous system (CNS) of bees. All the lowest concentrations have an effect on behaviour, higher concentrations lead to paralysis and death. Honeybees, or domesticated bees, are extremely important as pollinators of orchards.
The neonicotinoids clothianidin, imidacloprid and thiamethoxam are currently banned by the EU in all member states. This came into force by the end of 2018 by the European Commission. Both clothianidin and imidacloprid have a long half-life in soil. It takes at least 120 days for half of clothianidin to be deactivated, and at least 170 days for half of imidacloprid to be deactivated. This means that repeated use of these agents can lead to bioaccumulation in soil, plants and other life on or along the fields where it is used.
Thiamethoxam has a half-life of at least 40 days, and can kill bees on contact with as little as 0.02 micrograms (0.000.000.02 grams). Clothianidin and imidacloprid are also fatal for bees in contact with approx. 0.04 micrograms on the bee. Mortality occurs at concentrations around 0.005 micrograms on each bee if it enters through the mouth of the bee. But even lower concentrations than this can lead to a decline in bee populations due to the negative effects on behavior in the hive.
Lower concentrations of neonicotinoids have many harmful effects on bees and their colonies without killing them directly. Lower concentrations can damage reproduction, immune function, navigation, and behavior necessary for colony activities. This leads to reduced health and survival in hives. The colonies in the hive can be reduced to the point that all important activities collapse.
In the United States in 2014, these three different types of neonicotinoids were responsible for more than 90% of acute exposure to insecticide toxicity. A 4-fold increase in burden from 1992 to 2014 has been found for contact toxicity and a 48-fold increase in burden for oral toxicity such as e.g.. from nectar. The reason is a very large increase in the use of neonicotinoids on GMO seeds in the USA. In the EU, neonicotinoid seed treatments used on rapeseed are mainly used to kill the rapeseed flea (Psylliodes chrysocephala).
Almost all corn grown in the United States (about 36 million hectares) and about half of all soybeans (18 million hectares), and all cotton (5.5 million hectares.) are coated with neonicotinoid insecticide. Neonicotinoids are very water-soluble and can flow from these seeds into streams and water and kill aquatic insect species essential for fish and bird life. Altogether, the area is sown with neonicotinoid covered GMO seed 7% of the USA. This has a strong negative effect also on bees but also on songbirds.
Beneficial insects such as pollinators and pest predators must be outside the target of the insecticide. It is undesirable for insecticide to hit honey bees (Apis mellifera), bees that are bumblebees (Apidae). It is also undesirable to kill predators such as ground beetles (Chlaeius tricolor) which can kill snails, and insects such as flower flies (Sphaerophoria rueppellii) which feed on honeydew from phloem-feeding insects.
References:
https://www.sciencedaily.com/releases/2019/11/191127121340.htm
https://phys.org/news/2019-04-field-trial-neonicotinoids-honeybees-robust.html
https://www.inverse.com/article/59235-songbird-weight-loss-neonicotinoid-pesticide
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0783&from=EN
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0784&from=EN
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0785&from=EN
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