Cockroaches May Soon Be Unstoppable, Thanks To Fast-Evolving Insecticide Resistance

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Cockroaches May Soon Be Unstoppable, Thanks To Fast-Evolving Insecticide Resistance
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They’re lurking under your kitchen sink, they’re laced with a horde of germs, and now they’ve grown resistant to our weapons. Forget about their touted ability to survive a nuclear apocalypse… cockroaches are now resisting the chemicals specifically designed to kill them. New scientific research shows that a certain species of cockroaches is now resistant to insecticides.

Pesticide Resistance In Cockroaches

Pesticide-resistant cockroaches are not a new development. Exterminators actually use a cocktail of different insecticides with the hope that one of them will make the kill. This was the case until certain cockroaches developed cross-resistances. According to a 2019 study [1] published in Scientific Reports Journal, nearly all types of chemical insecticides were ineffective against German cockroaches (Blattella germanica L.)

Specifically, the scientists tested the impact of three potent insecticides on the population of German cockroaches in Illinois and Indiana. Over a period of 6 months, three colonies were exposed to thiamethoxam, abamectin, and boric acid. The researcher either applied a month-by-month rotation of the three pesticides, a mix of the different pesticides, or a single pesticide.

Rapid Evolution Of Cockroaches

Regardless of the treatment methods employed, the population of the critters didn’t change – it actually increased in the Illinois site. The scientists concluded that the cockroaches were quickly evolving and passing down the resistance as an inherited characteristic to the next generations.

This makes logical sense; as it does with other “single molecule insecticides” – the most resistant creatures survive, breed and develop a new generation with greater resistance. Attacking these again with the same insecticide merely selects the most resistant insects and means they will be the ones whose genes get passed on.

Did you know that a single German cockroach can produce over 10,000 descendants [2] within its life cycle of 100-200 days? Now assume that a small population develops resistance – within a few months, you’ll be looking at widespread insecticide resistance in the cockroach population. Whether this is a case of Darwin’s Theory of Evolution or not, the rapid evolution of German cockroaches is a real cause of concern.

Implications Of The Impeding “Cockroach Invasion”

Cockroaches are a threat to human health! The insects carry harmful bacteria such as Salmonella, Enterococcus, and E. Coli, which are a serious health risk. While this discovery on the invincibility of German cockroaches makes us consider getting a flame thrower, the solution lies in more subtle non-chemical methods.

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According to Purdue University professor and O.W. Rollins/Orkin Chair in the Department of Entomology, Michael Scharf [3], the approach needs to change. Control using chemicals alone is becoming almost impossible.

The researchers recommend an integrated approach to pest management, which involves combining improved sanitation, vacuuming, and traps with chemical treatments. Scharf believes that combining methods gives the greatest chance of getting rid of the pests, as opposed to over-reliance on insecticides.

Aside note – essential oils, having numerous active molecules, are often effective against insects and less likely to lead to resistant pests.

References:

[1] Fardisi, M., Gondhalekar, A. D., Ashbrook, A. R., & Scharf, M. E. (2019). Rapid evolutionary responses to insecticide resistance management interventions by the German cockroach (Blattella germanica L.). Scientific reports, 9(1), 8292 (via Nature Articles https://www.nature.com/articles/s41598-019-44296-y

[2] Penn State University. (2019). German Cockroaches (Department of Entomology). Retrieved 25 October 2019, from https://ento.psu.edu/extension/factsheets/german-cockroaches

[3] Service, P. (2019). Rapid cross-resistance bringing cockroaches closer to invincibility. Retrieved 25 October 2019, from https://www.purdue.edu/newsroom/releases/2019/Q2/rapid-cross-resistance-bringing-cockroaches-closer-to-invincibility.html


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