Artificial Sweetener Could Be New Tool in Cockroach Management

By John P. Roche, Ph.D.

German cockroaches (Blattella germanica) are a major global insect pest in urban buildings as purveyors of allergens as well as pathogens such as Salmonella, E. coli, and Rotavirus. Control of German cockroaches is usually done with insecticide sprays and insecticide-loaded baits, but cockroach populations can evolve resistance to insecticides, and insecticides can also affect non-target animals.

Researchers at the University of California, Riverside (UCR), are exploring the efficacy of a novel type of chemical control of German cockroaches—the artificial sweetener sucralose (also known as Splenda). In a study published in November 2023 in the Journal of Economic Entomology, the researchers found that sucralose-water solutions were effective in reducing survival of German cockroaches via effects on their gastrointestinal system.

In a previous study, the same research team—UCR’s Shao-Hung Lee, Ph.D., Dong-Hwan Choe, Ph.D., Michael Rust, Ph.D., and Chow-Yang Lee, Ph.D.—found widespread resistance to many commonly used insecticides among German cockroaches in California. Because insecticide resistance is a common problem, alternatives to traditional insecticides are needed. One avenue being explored is the use of artificial sweeteners, which “have been investigated for their insecticidal potential due to their inherently low mammalian toxicity,” Lee and colleagues write. Sucralose is one of the artificial sweeteners that has attracted the interest of researchers. “Since sucralose is widely used in food and beverage products,” Chow-Yang Lee says, “it is a ‘generally regarded as safe’ (GRAS) compound.”

In studies in 2021 and 2022, other researchers found that sucralose caused mortality in spotted wing drosophila (Drosophila suzukii). In the new study, the UCR team investigated sucralose’s effects on German cockroaches. They used four experimental tests:

1. a measure of how mortality varied with the concentration of sucralose provided;
2. a measure of how much water loss the cockroaches experienced following exposure to sucralose solutions;
3. a measure of how pre-exposure of cockroaches to sucralose affected dehydration leading to their mortality;
4. a test of how sucralose affected bacterial diversity in the guts of the insects.

In all of these tests, the cockroaches were placed in arenas containing dog food and a water source. In treatments where sucralose was provided, it was mixed with distilled water; control treatments provided only distilled water. The investigators used German cockroaches from three different strains: a strain that is susceptible to traditional insecticides (known as UCR) and two field-collected strains that are resistant to insecticides (known as WM and RG386).

Density-dependent mortality of German cockroaches was tested with 0 percent, 5 percent, 10 percent, and 20 percent sucralose solutions in the three different strains. For the susceptible UCR strain, Lee and colleagues found that survival sequentially decreased with higher sucralose concentration, and that all differences among concentrations were significant. For the WM strain, they found that survival was not significantly different between 0 percent and 5 percent sucralose solutions, but they did find significant differences in survival between 5 percent and 10 percent sucralose solutions and between 10 percent and 20 percent sucralose solutions. For the RG386 strain, they found no significant difference in survival between 0 percent and 5 percent solutions or 5 percent and 10 percent solutions, but they did find that survival was significantly lower with the 20 percent sucralose solution than with the 10 percent solution.

They also tested water loss in the cockroaches by comparing a 20 percent sucralose solution with a control solution of 0 percent sucralose over periods of zero, one, and two days. With greater time exposed to sucralose, they observed a greater reduction in body water.

The investigators tested for an effect of pre-exposure to sucralose by providing cockroaches with a 20 percent sucralose solution for two days prior to initiating measurements of mortality. In all three strains, they found significantly higher mortality in subjects pre-exposed to sucralose for two days compared to control subjects not pre-exposed. Meanwhile, the pre-exposed cockroaches experienced a decrease in water weight of between 23 percent and 30 percent after six days.

In their measurement of the effect of sucralose on gut species diversity in cockroaches, Lee and colleagues found that, for all three insect strains, when given a 20 percent sucralose solution for three days, gut bacterial diversity in the cockroaches was significantly lower than in control insects that were given only water.

The reduction in survival observed in German cockroaches following administration of sucralose seemed to result from dehydration caused by water loss. “Dehydrative mechanisms are seldom documented in conventionally used insecticides, which typically act primarily on the nervous system of insects,” Shao-Hung Lee says. “Traditional insecticide-resistance strategies recommend rotating among insecticides with different modes of action to avoid resistance development. The unique mechanisms of action of sucralose may fit well with this paradigm.”

The results of this study are promising, but additional research questions remain, the authors say. While sucralose has now been found to reduce survival in Blattella germanica and Drosophila suzukii, it is unknown whether sucralose would be effective for a broad variety of insect pests. Also, tests of sucralose on German cockroaches and spotted wing drosophila provided only one source of water and were conducted in lab settings. Lee and colleagues note that it will be important to also conduct tests in which sucralose solutions are presented to cockroaches along with a competing resource, as well as tests in real-world settings.

This study established sucralose as a potential tool in integrated pest management of German cockroaches. One aspect that is particularly attractive is the promise of the compound’s effectiveness against resistant strains. “What we are excited about is the unique mode of action of sucralose,” Chow-Yang Lee says, “which could potentially be used in the management of insecticide-resistant German cockroaches.” In addition, if formulated into a bait that could be effective, it could reduce the load of traditional insecticides entering the environment. Research on this promising compound is ongoing in Chow-Yang Lee’s group.

John P. Roche, Ph.D., is an author, biologist, and science writer with a Ph.D. and postdoctoral fellowship in the biological sciences and a dedication to making rigorous science clear and accessible. He authors books and articles, and writes materials for universities, scientific societies, and publishers. Professional experience includes serving as a scientist and scientific writer at Indiana University, Boston College, and the UMass Chan Medical School; serving as a visiting professor at four tier-one schools; and developing concept-based science curricula for universities and publishers.