How Do Bug Sprays (Like Raid and Baygon) Kill Cockroaches?

Contrary to popular belief, cockroaches cannot survive a nuclear explosion; however, it is true that cockroaches are more tolerant of certain ionizing radiation than humans. Even so, they cannot survive bug spray, as it consists of powerful neurotoxic substances.

Cockroaches are pretty amazing creatures. People who cringe at the sight of these little insects or find them disgusting may not share that opinion, but if you look at the feats that cockroaches are capable of achieving, you would agree too… probably.

A cockroach can hold its breath for almost 40 minutes, and can therefore survive being submerged in water for extended periods. It can live without water for a few days, without food for a month, and can even survive without its head for a few weeks!

Contrary to popular belief, cockroaches cannot survive a nuclear explosion, nor can they survive a run-in with their lethal enemy—bug spray.

The likes of Raid, Hit, Baygon and other popular brands are fatal to these roaches. So, how do these insecticides kill such tough and durable insects so quickly?

, How Do Bug Sprays (Like Raid and Baygon) Kill Cockroaches?, Science ABC, Science ABC

History

Humans have been using insecticides derived from natural sources since ancient times. Most of these strategies originally came from plant chemicals or chemicals like sulphur or sodium chlorate. Today, we have a broad arsenal of insecticides that we can spray to eliminate our bug problems. The origin of our modern anti-pest weaponry began in the 1940s with DDT and other synthetic chemicals.

The first generation of synthetic pesticides were not actually created to be pesticides. DDT was first synthesized in 1825 by chemist Othmar Ziedler, but it wasn’t until 1933 that Dr. Paul Muller observed its pesticidal properties. This discovery, as well as the Second World War, played a huge role in accelerating the discovery of synthetic pesticides.

The synthetic pesticides were much more efficient and could be designed to target pests in a specific way. This gave synthetic pesticides an edge over those used in the past.

How Bug Spray works

Bug sprays or insecticides are chemical compounds that work by inhibiting certain physiological functions. There are many different classes of insecticides that differ from each other in terms of how they are synthesized, how they affect the pest, and whether they affect all insects indiscriminately or are specific to a particular type or family.

, How Do Bug Sprays (Like Raid and Baygon) Kill Cockroaches?, Science ABC, Science ABC

A bug spray. Notice the composition printed on its cover.

Insecticides can be lethal in several different ways. Some insecticides act as neurotoxins, impairing the nervous system, some target respiration, preventing the insect from utilizing oxygen, while others might target the growth and reproduction of the insect.

Popular roach-killing bug sprays are a concoction of several different pesticides that fall under two broad types – pyrethoids and carbamates.

Pyrethroids are fast-acting compounds found in the majority of household insecticides and insect repellents. Pyrethroids are synthetic compounds, but they resemble a natural pesticide derived from daisy flowers called pyrethrin.

Pyrethrin is obtained from the ‘Pyrethrum daisy’, Chrysanthemum cinerariaefolium. The crushed flower was used as an insecticide for over 2,000 years. In fact, inhaling too much of the flower’s scent is harmful, as it might cause side effects like asthmatic breathing, sneezing, headaches, etc. Pyrethroids are chemically similar to pyrethrin, but are synthetically derived.

Pyrethroids are neurotoxic, affecting the functioning of a cockroach’s neurons, thereby paralyzing them. The chemicals target proteins that transport sodium and potassium across the neuron’s membrane. Neurons are able to send impulses due to the controlled entry and exit of these ions through the appropriate protein channels. Pyrethroids interfere with these channels, keeping them open, which impairs the ability of the neuron to work.

Another reason pyrethroids are a popular choice for bug sprays is that a very small dose of pyrethroids can kill roaches, but that same concentration is relatively harmless to humans. However, they may harm sensitive individuals or aquatic creatures (like fish) if applied directly in the water, as they dissolve very poorly.

allehtrin structure

The structural formula of Allethrin, a synthetic pyrethroid commonly found in bug sprays.

Some commonly used pyrethroids include allethrin, tetramethrin, resmethrin, cyfluthrin, permethrin and esfenvalerate. Also known as ‘first-generation pyrethroids’, these were primarily developed in the 1940s.

The other common chemical pesticide component of bug spray are carbamates. This class of pesticides are derived from carbamic acid.

These compounds target a specific enzyme called cholinesterase. This enzyme plays a role in degrading the neurotransmitter (a chemical messenger of the nervous system) acetylcholine. Acetylcholine is released by neurons to communicate with other neurons, as well as muscles, giving the latter a signal to contract.

Under normal function, the body allows acetylcholine to be present in the extracellular environment for a very short length of time. The cholinesterase enzyme breaks down the acetylcholine molecule, thereby preventing prolonged signaling to other neurons and muscles.

Carbamates prevent cholinesterases from degrading acetylcholine. This leads to the molecule continuously exciting other neurons, but more importantly, it causes the muscles to remain contracted.

This has serious consequences for muscles like the heart and those involved in respiration. The nerve impulse interference causes havoc throughout the insect’s body, which eventually leads to the insect’s death.

These and thousands of other insecticides are employed today to keep our homes, gardens and crops safe from a range of different pests. Their use has benefitted our standard of living and increased food crop yields, but there is a flip side to the story.

Many of these pesticides remain present in the soil and in the bodies of the animals that might breathe it in or consume it. When other animals feed on insects that ingested the pesticide or drink water from places with insecticide in it, unintended effects are often seen in these animals. This is called the bioaccumulation of pesticides.

The prolific environmentalist Rachel Carson cautioned our world against the overuse of pesticides. In her revolutionary book Silent Spring, she writes “A Who’s Who of pesticides is therefore of concern to us all. If we are going to live so intimately with these chemicals, eating and drinking them, taking them into the very marrow of our bones – we had better know something about their nature and their power.”

References:

  1. Archives of Toxology
  2. History of Pyrethroid Insecticides: Biotechnology and Biological Sciences Research Council
  3. History of Pesticide Use: International Union of Pure and Applied Chemistry
  4. University of Florida
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Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

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