About

Coby Schal is the Blanton J. Whitmire Distinguished Professor at North Carolina State University. His research focuses on urban entomology, chemical ecology, insect behavior, and physiology. Schal's work involves studying semiochemicals such as pheromones, the evolution of moth communication systems, mosquito oviposition, glucose-aversion in cockroaches, and other collaborations in chemical ecology and behavior. His contributions include investigating molecular mechanisms in olfaction, allergens, disease transmission, juvenile hormone mediation of behavior, population genetics, and rDNA evolution. Schal is actively involved in mentoring students and researchers within the Schal Lab at NC State, contributing significantly to the understanding of insect communication and behavior in urban environments.

Research topics

• Biology
• Zoology
• Medicine
• Genetics
• Veterinary medicine
• Evolutionary biology
• Ecology
• Toxicology
• Botany

Selected publications

• Cockroach gut microbiota is a significant source of endotoxin, a risk factor for asthma in cockroach-infested homes

  Journal of Medical Entomology · 2026-01-20

  articleOpen accessSenior author

  The German cockroach, an obligate indoor pest, produces potent aeroallergens whose presence, along with endotoxins, are often reported as important indoor predictors of increased risk of morbidity in sensitized asthmatic children. In our recent analysis, we found significantly higher endotoxin concentrations in household dust from cockroach-infested homes than from uninfested homes in the same communities. We also found that both female and male cockroaches excreted large amounts of endotoxin in their feces. In this study, we hypothesized that if the cockroach gut microbiota is the major source of endotoxin, then all life stages would be expected to excrete endotoxin in relation to their gut microbial abundance. Using the kinetic Limulus amebocyte lysate assay, we found high levels of endotoxin in the feces of all life stages of the cockroach. In both laboratory-maintained and recently field-collected cockroaches, adult females produced 2.5- to 3-fold more endotoxin than males, consistent with their larger body mass and greater food consumption. Nymphs produced less endotoxin than adults, but the endotoxin concentration (endotoxin per mg) was higher in nymph feces than in adult feces. We found trace amounts of endotoxin in the feces of adults with axenic guts lacking microbiota. Lastly, endotoxin in fecal residues remained stable for at least 30 days at ambient room temperature. These results reveal that cockroaches expose sensitized people to a mix of allergens that are potent asthma triggers and endotoxins that can exacerbate the allergic response. Further research is warranted to understand their combined effects on asthma sensitization and exacerbation.

  PublisherOA PDFDOI

• Two <i>Metschnikowia</i> nectar yeast species have similar volatile profiles but elicit differential foraging in bee pollinators

  Ecological Entomology · 2026-01-24

  articleOpen access

  Abstract Nectar yeasts are a highly specialized group of fungi that may play key roles in pollination ecology. Nectar yeasts lack an independent dispersal mechanism to access new habitats with fresh resources. Yeasts, bumble bee pollinators and flowering plants likely take part in a series of diffuse mutualisms, wherein yeast attract bees that provide phoretic travel between flowers. This interaction is thought to provide bees with improved foraging efficiency and plants with increased pollinator visitation and associated pollination services. However, the underlying mechanisms driving bee pollinator preferences for nectar with yeast and differences among yeast species in eliciting pollinator behavior are relatively unexplored. We used an integrative approach to elucidate the underpinnings of bee pollinator preference for nectars that contain yeasts. We conducted a survey of local flower nectar for presence and species diversity of yeast. Using two prominent, local nectar yeast species ( Metschnikowia reukaufii and Metschnikowia koreensis ), we conducted observational field trials to ascertain the effects of the presence and identity of nectar yeast on bee visitation rates. We also analyzed the volatile profiles of both yeast species to explore if olfactory cues were associated with differential foraging behavior. We found that M. reukaufii was the most common nectar yeast in our study area in the southeastern United States, as did previously published global surveys. Intriguingly, we found co‐occurrence of multiple yeast species in 22% of nectar samples, all of which contained M. reukaufii and another yeast typically from the Metschnikowia genus, such as M. koreensis . In a field trial, we found that bee pollinators had higher visitation to flowers supplemented with M. koreensis over sterile flowers, while no difference in bee foraging behaviour was evident in response to M. reukaufii . Despite this behavioural difference, the volatile profiles of both yeast species were not significantly different from one another. The ecology and species interactions of wild yeasts are poorly understood, yet may play vital roles in many ecosystems. Our research highlights the importance of studying facultative mutualisms and the necessity of testing their underlying assumptions. Elucidating the mechanisms behind insect‐microbe symbioses will open new horizons in pollination ecology and conservation.

  PublisherOA PDFDOI

• Bed bug preferences for host odor or aggregation odor are differentially modulated by physiological state in various odorscapes

  Pest Management Science · 2025-10-15

  articleOpen accessSenior authorCorresponding

  BACKGROUND: Bed bugs live in an ecologically and spatially restricted indoor habitat comprised of overlapping aggregation and host odors, and they traverse relatively short distances between blood-hosts and aggregation sites. Although many studies demonstrated aggregation or host odor preference respectively, the modulation of bed bug preferences between these divergent odors is poorly understood. Given the recurrent transitions of bed bugs between replete and hungry states, we evaluated the effects of six odorscapes containing aggregation and host skin odors on bed bug preferences. RESULTS: Hunger state modulated odor preference for aggregation and foraging in all tested odorscapes. Aggregation odor attracted both fed and unfed bed bugs. Host skin odor attracted unfed bed bugs but repelled recently fed bed bugs and the addition of carbon dioxide to host odor enhanced the behavioral responses. These findings suggest that orientation to aggregation sites in fed bed bugs is driven by two distinct odor-processing mechanisms for attractant and aversive odors. Unfed bed bugs discriminate between two attractive odors-aggregation and host odors-but host odor predominates over aggregation odor in driving their orientation behavior. CONCLUSION: Understanding the dynamic switching of odor preferences during the blood digestion cycle will guide the implementation of chemical lures in integrated pest management. Host odors alone and their co-emission with aggregation pheromone repelled fed bed bugs from traps. Conversely, unfed bed bugs had a strong preference for host odor emitted either alone or with aggregation odor. Therefore, the independent use of either host or aggregation odor lures and their co-emission from the same trap should be carefully considered. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

  PublisherOA PDFDOI

• Indoor allergens and endotoxins in relation to cockroach infestations in low-income urban homes

  Journal of Allergy and Clinical Immunology Global · 2025-09-27 · 2 citations

  articleOpen accessSenior author

  Background: Cockroach allergens are well recognized as important risk factors in the development and prevalence of allergic rhinitis and asthma in children, especially in low-income urban households. The German cockroach gut hosts a diverse community of highly abundant microbes, including gram-negative bacteria that shed large amounts of endotoxins in cockroach feces. Objective: We sought to delineate the causal relationship between the presence of cockroaches in homes and levels of household endotoxins. Methods: In laboratory assays, we measured the amount of endotoxin produced by cockroaches. In-home monitoring estimated the size of the cockroach population in each home and quantified cockroach allergen Bla g 2 and endotoxin levels in household dust and on heating, ventilating, and air-conditioning (HVAC) filters. An environmental intervention was implemented in a subset of the infested homes to eliminate cockroaches. Bla g 2 and endotoxin levels were quantified for 6 months after the intervention. Results: Large amounts of endotoxin are excreted by female (2900 endotoxin units [EU]/mg feces) and male (1400 EU/mg) cockroaches. At baseline, household dust and HVAC filters in infested homes had significantly higher levels of allergen (Bla g 2) and endotoxin than uninfested homes. Environmental intervention resulted in significant declines in cockroaches as well as allergen and endotoxin levels. In contrast, cockroach numbers and allergen and endotoxin concentrations remained high in infested-control homes. Conclusions: Cockroaches are a significant source of both endotoxins and potent allergens, potentially resulting in coexposure of asthmatic children to both.

  PublisherDOI

• Deployment and transcriptional evaluation of nitisinone, an <scp>FDA</scp> ‐approved drug, to control bed bugs

  Pest Management Science · 2025-01-25 · 2 citations

  articleOpen access

  BACKGROUND: Bed bugs are blood-feeders that rapidly proliferate into large indoor infestations. Their bites can cause allergies, secondary infections and psychological stress, among other problems. Although several tactics for their management have been used, bed bugs continue to spread worldwide wherever humans reside. This is mainly due to human-mediated transport and their high resistance to several classes of insecticides. New treatment options with novel modes of action are required for their control. In this study, we evaluated the use of nitisinone (NTBC), an FDA-approved drug, for bed bug control in an insecticide-susceptible (HH) and an insecticide-resistant (CIN) population. RESULTS: Although NTBC was lethal to both populations when administered orally or applied topically in very low doses, we observed a slight but significant resistance in the CIN population. Transcriptomic analysis in both populations indicated that NTBC treatment elicited a broad suppression of genes associated with RNA post-transcriptional modifications, translation, endomembrane system, protein post-translational modifications and protein folding. The CIN population exhibited higher adenosine triphosphate (ATP) production and xenobiotic detoxification. Feeding studies on a mouse model suggest that NTBC could be used as a control method of bed bugs by host treatment. CONCLUSION: The results indicate that NTBC can be used as a new active ingredient for bed bug control by topical or oral treatment and shed light on the molecular mechanisms of suppressed tyrosine metabolism following NTBC treatment. © 2025 Society of Chemical Industry.

  PublisherOA PDFDOI

• Two Metschnikowia nectar yeast species have similar volatile profiles, but elicit differential foraging in bee pollinators

  2025-06-18 · 1 citations

  preprintOpen access

  1. Nectar yeasts are a highly specialized group of fungi that may play key roles in pollination ecology. Nectar yeasts lack an independent dispersal mechanism to access new habitats with fresh resources. Yeasts, bumble bee pollinators, and flowering plants likely take part in a series of diffuse mutualisms, wherein yeast attract bees that provide phoretic travel between flowers. This interaction is thought to provide bees with improved foraging efficiency and plants with increased pollinator visitation and associated pollination services. However, the underlying mechanisms driving bee pollinator preferences for nectar with yeast and differences among yeast species in eliciting pollinator behavior are relatively unexplored. 2. We used an integrative approach to elucidate the underpinnings of bee pollinator preference for nectars that contain yeasts. We conducted a survey of local flower nectar for presence and species diversity of yeast. Using two prominent, local nectar yeast species (Metschnikowia reukaufii and Metschnikowia koreensis), we conducted observational field trials to ascertain the effects of the presence and identity of nectar yeast on bee visitation rates. We also analyzed the volatile profiles of both yeast species to explore if olfactory cues were associated with differential foraging behavior. 3. We found that M. reukaufii was the most common nectar yeast in our study area in the Southeastern USA, as did previously published global surveys. Intriguingly, we found co-occurrence of multiple yeast species in 22% of nectar samples, all of which contained M. reukaufii and another yeast typically from the Metschnikowia genus, such as M. koreensis. In a field trial we found that bee pollinators had higher visitation to flowers supplemented with M. koreensis over sterile flowers, while no difference in bee foraging behavior was evident in response to M. reukaufii. Despite this behavioral difference, the volatile profiles of both yeast species were not significantly different from one another. 4. The ecology and species interactions of wild yeasts are poorly understood, yet may play vital roles in many ecosystems. Our research highlights the importance of studying facultative mutualisms, and the necessity of testing their underlying assumptions. Elucidating the mechanisms behind insect-microbe symbioses will open new horizons in pollination ecology and conservation.

  PublisherOA PDFDOI

• First evidence of the A302S <i>Rdl</i> insecticide resistance mutation in populations of the bed bug, <i>Cimex lectularius</i> (Hemiptera: Cimicidae) in North America

  Journal of Medical Entomology · 2025-03-14 · 5 citations

  articleOpen access

  The common bed bug, Cimex lectularius (L.) (Hemiptera: Cimicidae), is a pervasive indoor pest with prominent medical, veterinary, and economic impacts. Bed bug infestations are controlled by a wide range of insecticides, including pyrethroids, neonicotinoids, pyrroles, and phenylpyrazoles; however, bed bugs have evolved resistance mechanisms to most of these insecticides. Mutations in the Rdl (resistance to dieldrin) gene, located in a subunit of the γ-amino butyric acid (GABA)-gated chloride channel, have been identified in several pest insects, including the German cockroach. These have been found to confer resistance to fipronil, a phenylpyrazole insecticide commonly used in urban environments, in addition to cyclodienes (eg dieldrin), a class of insecticides banned in most countries since the 1990s. While resistance to dieldrin and fipronil has been reported in bed bugs, both C. lectularius and the tropical bed bug, C. hemipterus, the occurrence of mutations in the Rdl gene has yet to be thoroughly investigated. In this study, we sequence a fragment of the Rdl gene commonly found to harbor cyclodiene and phenylpyrazole conferring mutations from 134 unique populations collected across the United States and Canada spanning a 14-yr period. Homozygous genotypes for the A302S mutation were found in 2 geographically distinct populations. This finding represents the first record of a non-synonymous Rdl mutation in bed bugs and identifies another mechanism by which insecticide resistance may be conferred in this species.

  PublisherOA PDFDOI

• Visual cues enhance effectiveness of pheromone-baited traps for the corn earworm moth, <i>Helicoverpa zea</i> (Lepidoptera: Noctuidae)

  Journal of Economic Entomology · 2025-02-13 · 7 citations

  articleOpen accessSenior author

  Mate-finding and host localization by nocturnal moths are predominantly mediated by olfactory signals and cues, respectively. Nevertheless, some nocturnal moth species rely on olfactory and visual cues to locate resources, such as flowers. Although traps are indispensable for the detection and monitoring of corn earworm moths, Helicoverpa zea (Boddie), a generalist and highly destructive crop pest, the role of visual cues in locating a pheromone source is poorly understood. Here, we investigated whether trap color influences the trap catch of the corn earworm. We showed that trap design affected male H. zea trap catch, with Hartstack-type traps being more effective than bucket traps, and more H. zea males were trapped in light-colored traps (white, yellow). However, under the dim ambient night conditions, when H. zea males fly, it is unlikely that they can discern trap colors. Instead, it is probable that H. zea males discriminate traps on the basis of their gray-scale reflectance, ranging from white to black. We found a positive correlation between trap captures and the relative luminance of dyed cheesecloth fabrics that we wrapped around Hartstack traps. Our findings suggest that at night, H. zea integrates the visual contrast between the trap and foliage background (ie apparency of the trap) in locating sex pheromone-baited traps.

  PublisherDOI

• Wolbachia-supplemented B-vitamins are critical for blood digestion in the bed bug Cimex lectularius

  Scientific Reports · 2025-11-20

  articleOpen accessSenior author

  Wolbachia, a bacterial endosymbiont, acts as an obligate nutritional mutualist in the bed bug, Cimex lectularius. Wolbachia in C. lectularius (wCle) supplements B-vitamins, namely riboflavin (B2) and biotin (B7), which are deficient in the bed bug's diet of vertebrate blood. Experimental elimination of wCle significantly impairs fitness in bed bugs, resulting in slow development, low egg production and egg hatch rate, and smaller adult body size. Although this obligatory symbiosis has been well-documented, the specific physiological mechanisms by which wCle-supplemented B-vitamins promote bed bug fitness remain unclear. We hypothesized that B-vitamin deficiency impairs digestion in aposymbiotic bed bugs, and in this study we investigated the effects of wCle elimination on three digestive processes in the bed bug - diuresis, erythrocyte (red blood cell) lysis, and protein catabolism. Our results show that wCle elimination significantly slows both diuresis and protein catabolism. We also demonstrate that riboflavin is critical for the breakdown of hemoglobin, the main protein component of red blood cells, but not albumin, the main protein component of plasma. We propose that the lack of wCle-supplemented riboflavin results in systemic protein deficiency, driving various fitness-related deficits in aposymbiotic bed bugs. These findings enhance our understanding of bed bug digestive physiology and the wCle-bed bug nutritional mutualism, with broader implications for other blood-feeding arthropods.

  PublisherOA PDFDOI

• An odorant-binding protein functions in fire ant social immunity interfacing with innate immunity

  Open Biology · 2025-02-01 · 6 citations

  articleOpen access

  Social immunity-mediated sanitation behaviours occur in insects when microbially killed corpses are removed and/or dismembered by healthy nestmates. However, little is known concerning the chemical signals or receptor proteins that mediate these responses. Here, we identify cuticular components in the eusocial red important fire ant, Solenopsis invicta : behenic acid, which induces dismemberment behaviour, and oleic and cis , cis -9,12-linoleic acids, which inhibit dismemberment in a process mediated by S. invicta odorant-binding protein-15 (SiOBP15). Yeast two-hybrid screening and protein–protein interaction analyses identified the ant immunity-related proteins apolipophorin-III (SiApoLp-III) and fatty acid binding protein-5 (SiFABP5) as SiOBP15 interacting partners. SiOBP15 and SiFABP5 bound all three dismemberment-related compounds, whereas interactions between SiOBP15 and SiApoLp-III narrowed binding to behenic acid. RNAi-mediated gene expression knockdown of SiOBP15 , SiApoLp-III or SiFABP5 revealed that behenic acid chemoreception determines dismemberment behaviour via SiApoLp-III/SiOBP15, whereas SiOBP15 or SiOBP15/SiFABP5 recognition of linoleic acid inhibits dismemberment behaviour. These data identify a host circuit linking olfactory proteins and proteins involved in innate immunity to control the degree of sanitation behaviour elicited in response to microbial infection. We identify specific chemical cues transduced by these proteins, providing a mechanism connecting olfaction-related processes to innate immunity, host–pathogen interactions and social immunity.

  PublisherDOI

Recent grants

• NIH Grant R01HD021891

  NIH · $125k · 1990

• Neuronal Reorganization Underlies Evolution of Novel Adaptive Behavior

  NSF · $650k · 2016–2021

• Evolution of Mating Communication in Moths: Role of Male Courtship Pheromones

  NSF · $579k · 2015–2019

• Evolution of the pheromone signaling system of Spodoptera frugiperda and Heliothis virescens

  NSF · $465k · 2011–2015

• Collaborative Research: Rapid and Pervasive Mitochondrial Heteroplasmy with Recombination in a Remerging Ectoparasite

  NSF · $82k · 2018–2022

Frequent coauthors

• Richard G. Santangelo

  North Carolina State University

  76 shared

• Edward L. Vargo

  Texas A&M University

  64 shared

• Warren Booth

  Virginia Tech

  52 shared

• Francis X. Webster

  SUNY College of Environmental Science and Forestry

  44 shared

• Satoshi Nojima

  Tokyo University of Agriculture

  44 shared

• Wendell L. Roelofs

  44 shared

• Ayako Wada‐Katsumata

  North Carolina State University

  34 shared

• Д. В. Муха

  Russian Academy of Sciences

  31 shared

Labs

• Schal LabPI

  Urban Entomology, Chemical Ecology, Insect Behavior & Physiology

Education

• Ph.D., Entomology

  North Carolina State University

  1996

• M.S., Entomology

  North Carolina State University

  1992

• B.S., Entomology

  University of California, Davis

  1989

Awards & honors

• J. Whitmire Distinguished Professor