Since the advent of Rachel Carson’s revolutionary book, Silent Spring, pesticides have come under increased scrutiny from the global community. However, after the banning of the DDT, one of the first synthetic insecticides, new harmful chemicals have been developed for pest control. Neonicotinoids, or neonics for short, are a class of potent insecticides that took the world by storm in the 1990s. Even though they were initially hailed for their potency and low risk to vertebrates, new research is starting to suggest that they may be more destructive than initially thought. 

Neonicotinoids encompass several different types of insecticides, with some of the most common names being acetamiprid, nitenpyram, thiacloprid, and thiamethoxam. The first type to reach the shelves was imidacloprid, which was found to be effective when applied to soil. Since then, neonics have become the most commonly used type of pesticide. Their popularity comes in part due to the way they work—neonics bind to the neurons of their targets, destroying them through overstimulation. In addition, they were touted because of their supposedly low-toxicity to helpful insects, such as bees.

However, a lot of the preliminary studies regarding neonics were inconclusive at best, leading many to start questioning the safety of the chemicals. Finally, in 2017, the largest study about the effect of neonics was conducted by a team of researchers and funded by the Centre for Ecology and Hydrology in the U.K. The experiment concluded that “neonicotinoids negatively affect pollinator health under realistic agricultural conditions,” pointing to the insecticides’ detrimental impacts on bees. Almost immediately, the study faced pushback from the industry. Large pesticide-producing companies like Syngenta vocally opposed the paper, labeling its results inconsistent and unfair. 

So what actually makes neonicotinoids harmful? For one, the pesticides are “systemic,” which means that they can be absorbed by plants because of their solubility. As a result, all parts of a plant can remain toxic for years after neonic application. They can also easily be transferred from species to species through a syrupy liquid known as honeydew, which is excreted by an order of insects known as Hemiptera. Through honeydew, these bugs can pass on neonic contamination to non-target species. 

Primarily, neonics are known for their damaging effects on bees. They have been linked with the decline of many colonies, an important issue due to growing concerns about declining pollinator populations. In addition, neonics can interfere with bees’ ability to find nectar, remember where certain flowers are located, and return to their hive. Furthermore, neonicotinoids can harm butterflies, fish, and other invertebrates, as well as potentially pose a threat to our drinking water and health. There is still extensive research that needs to be done in order to truly understand the scope of neonic contamination.

For now, it’s best for both companies and consumers to avoid using neonics as much as possible. Instead of trying to replace them with other insecticides, substituting in agroecological practices like crop rotation can be much more eco-friendly. There are also certain microorganisms that can be used as control agents, such as the bacteria Bacillus thuringiensis. In the end, whether it’s DDT or neonicotinoids, humans need to be incredibly cautious when using pesticides because of the widespread damage they can cause to the world around us.

 

written by Keerthi Selvam

edited by Saanvi Gutta and Tryphena Pilli

 

Image source: https://www.countryliving.com/gardening/g32157369/flowers-that-attract-bees

 

References:

Cressey, D. (2017). Largest-ever study of controversial pesticides finds harm to bees. Nature. https://doi.org/10.1038/nature.2017.22229

Frank, S. D., & Tooker, J. F. (2020). Neonicotinoids pose undocumented threats to food webs. Proceedings of the National Academy of Sciences, 117(37), 22609–22613. https://doi.org/10.1073/pnas.2017221117

Raichel, D. (2018). 10 Things You Always Wanted to Know About Neonics. NRDC. https://www.nrdc.org/experts/daniel-raichel/ten-things-you-always-wanted-know-about-neonics

Usta, C. (2013). Microorganisms in Biological Pest Control — A Review (Bacterial Toxin Application and Effect of Environmental Factors). Current Progress in Biological Research. https://doi.org/10.5772/55786

What is a neonicotinoid? (2015, December 29). Insects in the City. https://citybugs.tamu.edu/factsheets/ipm/what-is-a-neonicotinoid/

Woodcock, B. A., Bullock, J. M., Shore, R. F., Heard, M. S., Pereira, M. G., Redhead, J., Ridding, L., Dean, H., Sleep, D., Henrys, P., Peyton, J., Hulmes, S., Hulmes, L., Sárospataki, M., Saure, C., Edwards, M., Genersch, E., Knäbe, S., & Pywell, R. F. (2017). Country-specific effects of neonicotinoid pesticides on honey bees and wild bees. Science, 356(6345), 1393–1395. https://doi.org/10.1126/science.aaa1190