Editor’s note: PCT caught up with North Carolina State University’s Dr. Coby Schal, one of the foremost cockroach authorities. Schal authored the Cockroach chapter in the 10th edition of the Mallis Handbook of Pest Control (order at http://bit.ly/29chPdF). In the following Q&A, Schal discusses why he enjoys working with cockroaches and provides a glimpse at some of the research the N.C. State team is performing.
PCT: Why is the cockroach such a popular subject of entomological research? What makes this pest so interesting to researchers?
COBY SCHAL: Researchers often seek “model systems” that best address specific questions, but are also convenient to maintain in a lab. This is why the mouse and fruit fly are workhorses of biomedical and genetics research, respectively. The cockroach has been a workhorse of insect physiology — the study of structure and function of whole organisms and of specific organ systems. Size matters since each insect organ is tiny! The larger cockroach species (Periplaneta americana and some of the blaberid species; refer to the Mallis chapter to learn about these species!) have been indispensable for research in insecticide discovery, toxicology, endocrinology (this is where some of the juvenile hormone analogs came from), molting and cuticle formation, and many other areas. These big roaches are used in biobot research because they are long-lived, hardy, can carry large payloads and serve as inspiration for biologically-based robots. To evolutionary biologists, roaches represent a very old lineage from which we can learn a lot about the evolution of hemimetabolous development (learn more about this in the Mallis chapter) and the emergence of sociality in cockroaches and termites. And, of course, if we want to eradicate pest roaches, we need to identify weak links in their biology as targets for pest control; this requires research.
PCT: Does the pest management industry do a good job of educating the public about the public health impact of cockroaches, particularly as it relates to cockroach allergens? Why or why not?
CS: An emerging link between an environmental factor and human health, however tenuous, is rapidly picked up by the media, and covered in the news, self-help guides and doctors’ offices. By contrast, the medical importance of cockroaches is astonishingly poorly recognized by the public as well as the medical and regulatory communities. Cockroaches have been recognized for half a century as major triggers of respiratory disease, including allergies and asthma. We also have known for decades that they can transmit pathogenic microbes, including multi-drug resistant bacteria. Yet the public is largely unaware of this link. The pest management industry has done an excellent job educating the public about the potential economic losses from termites, carpenter ants and wood-boring beetles. But we have not done as well communicating the potential health impacts of cockroach infestations. When it comes to indoor pests that can cause disease, such as cockroaches and bed bugs, I’d like to see greater emphasis on public education and more efforts toward pest eradication. We have an excellent toolbox for eliminating cockroaches and the allergens they produce, but many consumers still rely on much less effective do-it-yourself products.
PCT: What is the most important finding for PMPs from the recent cockroach glucose aversion research your laboratory at North Carolina State University conducted?
CS: This research, in collaboration with Dr. Jules Silverman and Dr. Ayako Wada-Ktsumata, is groundbreaking because for the first time it uncovered the physiological basis for the rapid evolution of a new highly adaptive behavior in cockroaches in response to insecticide baits. We have known for decades that cockroach populations can rapidly develop resistance to insecticides through various genetic modifications in biochemical processes (mainly metabolic detoxification of the insecticide). But here, we found that a change in the sensory system (taste) can drive behavioral resistance to the bait. These findings inform us that roaches have a plethora of new, previously unknown mechanisms in their toolbox that they can recruit in their arms race with us. These findings will also guide the development of new baits that will circumvent these adaptations in the cockroach. Bait manufacturers rapidly responded to glucose aversion by innovating and reformulating cockroach baits. But recently we found fructose-avoiding cockroaches, and we suspect that roaches quickly evolve to impede our pest management efforts. There are three main things the PMP can do in the short-term: (1) conduct “taste tests” with cockroach infestations — offer them several baits and let the roaches guide which bait should be used; (2) rotate among baits with different modes of action to delay the emergence of resistance to the active ingredients; and (3) alert us when you encounter major control failures with properly deployed baits. We are very interested to discover how cockroaches innovate in response to our pest control advances.
PCT: What did industry icon Blanton Whitmire mean to you and the pest management industry?
CS: Blanton revolutionized the pest management industry in several ways. First, he so well understood the power of biology and behavioral observations as a gateway to innovations. He argued, as we all still do, that a central tenet of pest management is to properly target each pest based on its behavior — the “crack & crevice” treatment is an excellent example, and now an industry standard. Second, Blanton invested in a long-term collaborative relationship with Dr. Charles Wright at N.C. State, and this expedited industry innovations, academic training and research. Third, Blanton valued the importance of PMP education and promoted the vision that the No. 1 industry challenge is education. He developed and vehemently supported the Whitmire Scientific Symposium. He maintained that innovation, education, and efficacious products are the best investments in the company’s future. Fourth, Blanton’s philanthropy and generosity were evident as president and CEO of Whitmire Research Laboratories, but even more so in retirement; he and his wife Peg endowed four professorships at three universities, a major addition to the Missouri Botanical Gardens and they generously supported their St. Louis community. Blanton and Peg’s gifts to our Urban Entomology program at N.C. State University have enabled us to cultivate an integrated research and extension team, higher-risk research endeavors and training of the next generation of urban entomologists. There is a short write-up about the Whitmires at http://www.cals.ncsu.edu/entomology/schal_lab/BlantonJWhitmireEndowment.
PCT: What do you see as future research needs of the industry as it relates to cockroaches?
CS: There are so many unknowns! We are well on our way to sequencing the full genome of the German cockroach. This community resource will reveal genes, biochemical pathways, and neurogenetic networks that are unique to the cockroach and therefore potential targets for novel and specific pesticides. It will likely reveal mutualistic associations with microbes that may be targets for disruption. I think baits will continue to dominate as the most efficacious formulation against cockroaches. Therefore, we will need to determine the frequency of glucose aversion in the U.S. and globally; investigate the relationship between glucose aversion and the evolution of metabolic resistance to insecticides; screen cockroach populations for aversion to other sugars and other nutrients; determine whether cockroaches learn and remember aversive stimuli (that is, glucose-containing baits) better or worse than rewarding stimuli; and finally, delineate the molecular genetic mechanisms of glucose aversion. Biological control of cockroaches has been relatively ineffective — why? Do cockroaches have a fantastically effective immune system? We discovered a highly species-specific virus that is pathogenic but very slow. Perhaps slight genetic modifications can make it more virulent as a pest control agent. We also need to investigate the impact of effective cockroach control on the allergens they leave behind and on associated health-related outcomes, especially in children. At the broader ecological level, international travel and commerce can lead to the emergence of new invasive pests. There are some cockroach species that associate with the built environment in Southeast Asia and Africa and we need to keep an eye on their global spread, as the Asian cockroach is marching west through Texas and into Mexico and north into North Carolina. Finally, an important question with the German cockroach (and bed bugs) is what adaptations facilitate their tight association with us. The German cockroach does not occur anywhere else in nature, whereas its close relative the Asian cockroach lives strictly outside. Why, and what biological traits and adaptations enable these ecological associations?