Bacteria in the genus Wolbachia are commonly found living within insects, but their presence in cockroaches has not been thoroughly explored. A new study finds Wolbachia in four of 16 cockroach species across three families, and researchers hope further study may open doors to new management methods for pest cockroach species. The cockroach species examined in the study include: 1. Eurycotis floridana, 2. Blatta lateralis, 3. Periplaneta fuliginosa, 4. Periplaneta americana, 5. Balta notulata*, 6. Supella longipalpa*, 7. Blattella germanica, 8. Blattella asahinai, 9. Blattella vaga, 10. Pseudomops septentrionalis*, 11. Nauphoeta cinerea, 12. Gromphadorhina portentosa*, 13. Diploptera punctata, 14. Schultesia lampyridiformis, 15. Blaptica dubia, and 16. Leucophaea maderae. Species in red in the image and starred in this caption were found to harbor Wolbachia. (Image by Seun Oladipupo, Ph.D.)

By Seun Oladipupo, Ph.D.

Seun Oladipupo, Ph.D.

Insects are fascinating! Yet, insects can also be a source of nuisance. For example, cockroach infestations in homes can be a source of allergen triggers, mechanical vectors of pathogens, and embarrassment to homeowners as cockroaches often move from filth to food in homes and are perceived as a sign of poor hygiene/sanitation. Cockroach management often relies heavily on the use of insecticides and sprays, which, due to evolving resistance among some cockroach populations, no longer provide the anticipated level of control. However, there may be a new avenue for cockroach control using knowledge of cockroach endosymbionts like Wolbachia.

Wolbachia is a type of bacteria found living within many insects. The bacterium is passed from a mother to its offspring. To ensure this, Wolbachia manipulates the reproductive biology of its insect host. For example, Wolbachia can kill all the males in an insect population. Wolbachia can modify sperm making it toxic to eggs. Wolbachia can turn biological males into females. Also, Wolbachia can promote host dependence by providing essential nutrients.

The type of Wolbachia-mediated reproductive manipulation, however, depends on the strain found in an insect. In a new study published in May in the Journal of Economic Entomology, my colleagues at Auburn University and Aix Marseille Université and I explored the possibility of Wolbachia as a potential tool to control cockroaches. We screened 16 cockroach species across three families—Ectobiidae, Blattidae, and Blaberidae—for the presence of Wolbachia. The goals were to (1) uncover the frequency of Wolbachia in intractable cockroach species like the German cockroach (Blattella germanica), (2) determine the Wolbachia strain in the Wolbachia-infected cockroaches, and (3) predict the type of Wolbachia-mediated reproductive manipulation. Taken together, such knowledge could give insights that could be exploited for effective cockroach control.

Our study found that Wolbachia is relatively uncommon among cockroaches, infecting only about 1 in 4 cockroach species. For example, cockroach species such as Pseudomops septentrionalis (sometimes known as the pale bordered field cockroach) and Gromphadorhina portentosa (often known as the Madagascar hissing cockroach) were infected with Wolbachia. Disappointingly, the German cockroaches screened had no Wolbachia infestation.

Our research also found that the Wolbachia infecting cockroaches belong to the F clade Wolbachia. This is the same strain of Wolbachia found in termites and bed bugs. The F-clade Wolbachia provides its insect host with essential nutrients necessary for their growth and development. For example, Wolbachia provides bed bugs with biotin. Thus, Wolbachia-infected bed bugs profoundly produce more eggs and nymphs compared to uninfected bed bugs. We found that Wolbachia-infected cockroaches also produce biotin, suggesting possible nutritional benefits to cockroaches. However, since cockroaches have broad diets, more data and experiments are required to shed more light on the nutritional benefits of Wolbachia. Once clarified, baits seeded with antibiotics could be designed to eliminate Wolbachia in Wolbachia-infected cockroaches, depriving them of those nutritional benefits.

We acknowledge there is still much to be learned about the relationship between Wolbachia and cockroaches. For instance, how cockroaches acquired Wolbachia is still an open question. But, some of the data provided in this study suggest possible acquisition from bed bugs. It is not uncommon to find bed bugs and cockroaches in the same niche. Sometimes, cockroaches even feed on bed bugs. In addition, we are still working to understand the role that geography plays in Wolbachia infection frequency in cockroach species. For example, while Wolbachia was unreported in German cockroaches in this study (some of which were collected from the field near Auburn and some of which came from lab-maintained populations at the university), there are reports of Wolbachia-infected German cockroaches in Iran and China.

Even so, this study offers new insights into the relationship between cockroaches and Wolbachia. The presence of Wolbachia in cockroaches suggests that it may be possible to use Wolbachia as a tool for urban insect management in the future. Rather than relying on conventional insecticides, scientists may be able to exploit the relationship between Wolbachia and cockroaches to develop new and effective strategies for controlling cockroach populations that are both sustainable and safe for the environment.

Seun Oladipupo, Ph.D., is a postdoctoral research associate at Yale University who received his Ph.D. in entomology at Auburn University in 2022. Website: www.seunoladipupo.com. Email: seun.oladipupo@yale.edu.

Editor’s note: An earlier version of this article included a misspelling of Blattella asahinai in the primary image and accompanying caption. It has since been corrected.