Chemistry and Pesticides : NeonicotinoidsBy Brian Frank Pesticides are substances used to eradicate pests. Commercially, they are used on crops to stop them from being destroyed or damaged. While there are many different classes of pesticides, I have decided to focus on Neonicotinoids. Neonicotinoids are a class of chemical pesticides, that are chemically alike to nicotine (a natural insect repellant), and affect the neurological system of their targets (Neonicotinoids, 2018).They are most effective against sucking insects which happens to be why I chose to write about Neonicotinoids instead of one of the many other pesticides.
I’ve heard about the concerns and controversy regarding the decrease in the honey-bee population due to pesticides, and upon researching different pesticides to choose one, discovered that these were the ones alleged to be responsible for it. The first development of a Neonicotinoid was in 1970, by the chemist Henry Feur (Neonicotinoids, 2018), His first 1st synthesis was not quite right but with further attempts and modifications it eventually became Nithiazine. However, Nithiazine was broken down too easily by sinligjy, and this was not good for commercial use.
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The company Shell also did some research, but it wasn’t until 1985 when the company Bayer developed the first commercial Neonicotinoid, Imidaclopid. Since then, other companies have developed other types of Neonicotinoids beyond Nithiazine and Imidaclopid, such as Acetamiprid, Clotianid, Nitenpyram, Thiacloprid, and Thiamethhoxan, but Imidaclopid remains the most widely used (Neonicotinoids, 2018). Neonicotinoids are water soluble and they break down slowly, so they have a long lasting effect. With exposure to the sun they have a half life of 34 days, but they can take up to 3.8 years to degrade in the absence of sunlight (Neonicotinoids, 2018), which is a concern for environmentalists. Neonicotinoids are used on many different crops all over the world. Imidaclopid is the one in most wide-spread use, accounting for most of the commercial crop Neonicotinoid use in the world.
It is either added to the water sprayed on the crops, or the seeds are coated with it before they are planted. The way in which Neonicotinoids work, is that they bind to a certain cell receptor in the “pest” (Hayenga, 2018) they bind to the nicotinic acetylcholine receptor, which triggers a response in the pest (Neonicotinoids, 2018), most specifically insects. This binding to the cell receptor leads to the overstimulation and blocking of the receptors, which results in paralysis and death (Hayenga, 2018).the This binding is not reversible and the receptor that it blocks is much more plentiful and prevalent in insect’s, than in mammals and other creatures. The pros and cons of this kind of pesticide, are many and varied (Pros, 2017).
They have a unique selectivity of insect’s, which greatly helps the health of the crops by protecting them. They aid in disease control. This all results in a larger food supply and lower food costs. Neonicotinoids are easily and readily available, and they are extremely effective at getting rid of the unwanted pests. The cons are also many however, and while I will address them in more detail in the next section, they involve the negative impact on the environment, and the animal/insect population, as well as potential (although lesser) harm to humans. Obviously, Neonicotinoids help crops in many ways. They kill off most of the pests that would destroy or damage them. When the seeds are coated or when the water mixed with it is sprayed to the soil, it travels up the xyla and into the plant.
So when insects try to feed on the vegetation, they are ingesting the Neonicotinoid and ultimately killed. This, unfortunately, also effects the environment. The most talked about and controversial way in which that is done, is the decline of the honey-bee population (Beyond, 2015).
When the bees suck on the pollen or nectar of these plants during pollination, a natural, necessary event, they are poisoned by the Neonicotinoid. These deaths have resulted in something called honey bee colony collapse disorder (CCD) (Neonicotinoids, 2018). The population of these honey bees is dying out and they are in danger of becoming extinct if this continues at the rate it has been. The residues that that accumulate in the pollen and the nectar (Beyond, 2015) seems an almost unavoidable result of the use of Neonicotinoids on crops. And while other animals are vastly less affected by this directly because the composition and location of their receptors is different, indirectly it is taking it’s toll elsewhere as well. Certain bird populations are also declining due to the depletion of insects which are their main food source.
Other ways in which Neonicotinoids affect the environment is by polluting the water, soil, and even the air. Degradation of these very powerful pesticides is a big issue. Sometimes the concentration of it in a crop is so great that the soil becomes so contaminated with it, that new crops grown from the same soil are grown as if it had been applied to that crop as well. And the contamination of water makes it dangerous to other birds and animals that aren’t even threats to the crops to begin with. In summary, Neonicotinoids definitely serve their purpose, and they do it very effectively. There is no argument that claims that the use of them are not advantageous to the crops and farmers. However, the damage to the environment, especially to the bees and the birds, is not negligible and needs to be addressed.
Europe has far greater restrictions on Neonicotinoids. With some countries going as far as banning their use. And there have been many suggestions made for how to mitigate the damage Neonicotinoids do, and in some of them, chemists can definitely play a big role.