The German cockroach is a classic structural pest that has been well studied by urban entomologists for decades. As is the case with most heavily researched organisms, the likelihood of discovering something completely isn’t very high simply due to the extensive amount of research that’s already been conducted. Which is precisely what makes the publication featured in this blog post so exciting!  

Researchers are in a never-ending battle to find the next silver bullet in the battle against the German cockroach. One notable challenge with managing this species is that infestations are typically found in sensitive environments such as food preparation sites such as kitchens where treatment options may be limited because of the sensitive nature of these areas. To investigate new control solutions for these environments, scientists have been exploring the use of artificial sweeteners for their insecticidal potential against a range of urban pests. That’s right, the same artificial sweeteners such as sorbitol, xylitol, saccharin, aspartame, and sucralose that come in the blue, pink, or yellow packets used to sweeten your morning coffee or tea.  

Before we jump to any conclusions about the general safety of artificial sweeteners to humans, it's important to note that just because something is toxic to one organism doesn’t necessarily mean it’s toxic to ALL organisms. Take dark chocolate for example. Most people can eat dark chocolate without much issue, but the cocoa in this sweet treat can be highly toxic to dogs and could result in an emergency trip to the vet if your four-legged friend gets their paws on even a small piece. What makes artificial sweeteners an ideal candidate for insecticidal studies is that these substances have an inherently low mammalian toxicity but can cause some serious issues for many insects when consumed. Past studies testing the potential toxicity of many artificial sweeteners on a range of pests have had mixed results ranging from changes in motor function, decreased response to the opposite sex, reduced feeding, dehydration, and reduced survival. And, until recently, there was limited testing of artificial sweeteners on cockroaches.

 

 

Xin Su and colleagues set out to address this gap in knowledge by investigating the oral toxicity of sucralose on the German cockroach. To do so, they ran three different experiments. In all experiments they compared feeding results using two different groups of cockroaches. One group (the susceptible strain) was susceptible to insecticides while the second group (the resistant strain) was known to be insecticide resistant.  

In their first experiment, the researchers wanted to assess the oral toxicity of sucralose, so they fed both susceptible and resistant strains of German cockroach on sucralose at three separate concentrations: 5%, 10%, and 20%. What they found was that more German cockroaches died on average (ranging from 62.5% to 92.5%) at the 20% concentration. In the second experiment Su and colleagues measured the impact of water loss on both cockroach strains when fed the 20% sucralose solution. All strains lost 23.0-30.29% body water by day 6 of the experiment. And, not surprisingly, the more dehydrated cockroaches were more prone to mortality than nondehydrated German cockroaches. In the last experiment, they looked at gut bacterial composition after both strains were fed 20% sucralose and what they found was that the diversity of gut bacteria was significantly reduced after 3 days.  

The conclusion from their study was that German cockroaches fed a 20% sucralose solution had a higher mortality rate than lower concentrations, they were more dehydrated, and they had a decreased diversity of gut bacteria. Overall, these results are promising. Given the impacts that sucralose has on dehydration and gut microbiome, and its palatability to German cockroaches, researchers could start looking at this artificial sweetener as an additive to enhance the toxicity of existing baits or possibly even as a standalone active ingredient. However, it is important to note that this was a laboratory study where the cockroaches were not given a choice between the sucralose and other food sources. So, there’s still more work to do to confirm that hungry German cockroaches would prefer sucralose to competing alternatives. Nevertheless, this study does show promise and I expect we’ll be seeing more follow up studies on this in the near future!  

Article by Mike Bentley, PhD, BCE

References

Shao-Hung Lee, Dong-Hwan Choe, Michael K Rust, Chow-Yang Lee, Oral toxicity of an artificial sweetener sucralose on the German cockroach (Blattodea: Ectobiidae) and its impact on water balance and gut microbiome, Journal of Economic Entomology, Volume 117, Issue 1, February 2024, Pages 268–279, https://doi.org/10.1093/jee/toad206

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