About

Julio Bernal, Ph.D., is a Professor in the Department of Entomology at Texas A&M University, College Station. His research and teaching interests are in the fields of biological control and plant-insect interactions. Specifically, his research focuses on the ecology and behavior of natural enemies, particularly parasitoid wasps, and the evolution of herbivore defenses in crops, especially maize. His work aims to identify and develop pest management strategies that are effective, environmentally friendly, and evolutionarily sustainable. Over the last five years, his research has attracted $1.3 million in grant support. Bernal's teaching includes general entomology for undergraduates, pest management topics such as integrated pest management, host plant resistance, and biological control for graduate students, as well as agricultural evolution, including the evolution and impacts of agriculture and pest management. He advises or co-advises six Ph.D. students and has previously advised five Ph.D. and eight M.S. students. Bernal holds editorial roles as Biological Control Subject Editor for the Journal of Economic Entomology, Editor for Insects, and Associate Editor for Agroecology and Ecosystem Services for Frontiers in Sustainable Food Systems. His professional achievements include being a Fulbright Scholar, serving as President of the Sociedad Mexicana de Control Biológico, and acting as a Global Faculty Advocate for Mexico at Texas A&M University.

Research topics

• Biology
• Genetics
• Biotechnology
• Agronomy
• Ecology
• Evolutionary biology

Selected publications

• Maize leaf endosphere microbiome was affected by domestication and shows patterns consistent with microbial dysbiosis

  Frontiers in Microbiomes · 2026-02-23

  articleOpen access

  Background: Whether domestication, post-domestication spread, and breeding affected the maize leaf endosphere microbiota is poorly understood despite the well-known effects of those processes on the crop's genetics and responses to the environment. We examined the leaf endosphere microbial communities associated with three plant groups (Zea mays): teosintes, maize landraces, and maize elite inbreds. The teosintes group included Balsas (Z. mays parviglumis) and perennial (Zea diploperennis) teosinte, and each maize (Z. mays mays) group included genotypes from Mexico and USA. We used 16S-V4 region amplicon sequencing of the leaf endophytic microbiota to infer how the microbial communities of inbred maize may have been shaped by the crop's evolution, and whether they were affected by: (i) the transition from a perennial life history to an annual life history in the teosintes; (ii) domestication of maize from Balsas teosinte; (iii) northward spread of landrace maize from Mexico to the US; and (iii) breeding of landrace maizes to produce elite inbreds. Results: The leaf endophytic microbial community differed among the plant groups and genotypes, and was affected by domestication, as indicated by a decline in bacterial diversity and changes in microbial community structure between wild (teosinte) and domesticated (maize) Zea. While the microbial community structure was stringent and regulated in the teosintes, it was variable in the maize landraces and inbreds, as evidenced by greater distances to centroid based on Euclidean dissimilarity metric. This pattern was suggestive of microbial dysbiosis in the leaf endosphere associated with domestication and is consistent with predictions of the Anna Karenina principle. This finding marks the first evidence of dysbiosis associated with domestication. FAPROTAX predictions suggested that the teosintes may harbor microbial communities enriched in taxa associated with cellulolytic, chitinolytic, and nitrate respiration functions, while the maizes showed higher fermentation and nitrate reduction functions. Conclusions: Our results showed that the leaf endosphere microbial community structures in maize are consistent with alterations associated with dysbiosis. Our findings enhanced our understanding of the effects of anthropogenic processes including crop domestication, spread, and breeding on the leaf endosphere of elite maize cultivars, and may guide the development of evolutionarily-and ecologically sustainable biofertilizers and biocontrol agents.

  PublisherDOI

• Toxicity and Sublethal Effects of Synthetic Insecticides Against Goniozus legneri1

  Southwestern Entomologist · 2025-05-26

  articleSenior author

  Resumen. Toxicidad y Efectos Subletales de Insecticidas Sintéticos Sobre Goniozus legneri1 La compatibilidad del control químico con el control biológico es importante pero no es sencilla debido a que la mayoría de los insecticidas pueden afectar adversamente a los agentes de control biológico como el parasitoide Goniozus legneri (Gordh) (Hymenoptera: Bethylidae). El objetivo de la presente investigación fue evaluar, en condiciones de laboratorio, los efectos letales y subletales de los insecticidas comerciales espirotetramato (en mezcla con tiacloprid), bifentrina, pirimicarb e imidacloprid en el parasitismo y emergencia de adultos de G. legneri. Se emplearon las dosis de campo y 1/2, 1/4, 1/8 y 1/16 de ésta, por aspersión directa y exposición a una superficie tratada. Espirotetramato en mezcla con tiacloprid ocasionó la menor mortalidad (aspersión 12.2%, residual 13.3%) de G. legneri mientras que bajo aspersión directa, esta mezcla de insecticidas, en sus dosis altas, ocasionó la menor reducción tanto en parasitismo -2 .2% como en la emergencia de adultos de la F1 -23.2% con respecto al control. Bifentrina provocó un 100% de mortalidad de G. legneri en su dosis comercial y la mitad de ésta 4.0 y 8.0 g hl-1) al aplicarse directamente. En el caso de Pirimicarb la mortalidad fue superior en exposición a una superficie tratada (67.6%) que en aspersiones directas (24.7%). Imidacloprid asperjado directamente provocó una reducción completa del parasitismo y del desarrollo de la progenie de G. legneri -100% . Ningún tratamiento insecticida afectó o promovió la preferencia del parasitoide por larvas tratadas. Espirotetramato en mezcla con tiacloprid fue el insecticida menos tóxico para adultos de G. legneri mientras que Bifentrina e Imidacloprid fueron los más tóxicos.

  PublisherDOI

• Three‐dimensional flight analysis shows associative learning enhances foraging behavior of the specialist parasitoid, <i>Microplitis croceipes</i>

  Entomologia Experimentalis et Applicata · 2025-03-20 · 1 citations

  articleOpen access

  Abstract The reproductive fitness of parasitoids is dependent on their ability to find optimal hosts for oviposition and nectar/honeydew as a sugar source for survival and reproduction. Learning of ecologically relevant odors helps parasitoids refine their foraging behavior to enhance their reproductive success. However, little is known about how associative learning may help parasitoids optimize their flight behavior while foraging for food and/or hosts. This study compared the inflight behavioral responses of naïve and experienced Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) toward two ecologically relevant, host‐related volatile compounds, α‐pinene and α‐farnesene. Using wind tunnel bioassays, we tested the hypothesis that associative learning of ecologically relevant odors would improve the flight responses of M. croceipes females, resulting in oriented and motivated flight toward the odor sources. A behavioral tracking software, which records the flight behavior of insects in three dimensions, was used to track the inflight behaviors of naïve and experienced parasitoids to ecologically relevant odors (α‐pinene and α‐farnesene) and compare relevant flight‐related parameters (response time, time in upwind flight, speed, angular velocity, and tortuosity). The results showed that associative learning significantly improved the foraging behavior of M. croceipes females. Odor learning resulted in more directly oriented upwind flight toward odor sources compared to naïve females. In addition, comparisons of individual flight parameters revealed that learning enables parasitoids to adapt to specific cues, thereby increasing responsiveness and attractiveness to the learned odor. These findings highlight the adaptive significance of associative learning during foraging and host location strategies in parasitoids.

  PublisherOA PDFDOI

• Susceptibility of Apis mellifera to Bacillus thuringiensis Berliner, nuclear multiple polyhedrosis virus, azadirachtin, pyrethrins, and abamectin

  Research Square · 2025-04-29

  preprintOpen access
  PublisherOA PDFDOI

• Oviposition Preference of <i>Chelonus insularis</i> Females, a Parasitoid of <i>Spodoptera frugiperda</i> , Does Not Match Their Offspring's Performance

  Entomologia Experimentalis et Applicata · 2025-12-19

  articleCorresponding

  ABSTRACT Chelonus insularis (Cresson) (Hymenoptera: Braconidae) is an egg‐larval parasitoid of the fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae). Previous studies reported that maize plants can affect the performance of FAW as well as that of its parasitoids. However, there is little information about whether plants affect the performance of egg‐larval parasitoids of FAW. It is also unknown whether C. insularis females can perceive cues from different maize cultivars and therefore preferentially parasitize hosts on which their offspring's performance is highest. In this study, we compared the preference and performance of C. insularis on three maize cultivars: the Mexican landrace Tuxpeño, the inbred B73 from the United States, and inbred isoline B73‐lox10, a B73 mutant deficient in the production of jasmonic acid, green leaf volatiles, and herbivore‐induced plant volatiles. Oviposition of C. insularis females and colonization preferences of FAW neonate larvae parasitized by C. insularis were assessed using three‐choice cage tests in a greenhouse. The offspring sex ratio, adult weight, development time, and longevity were used as indicators of parasitoid performance. C. insularis performance was highest on B73‐lox10 plants, lowest on Tuxpeño plants, and intermediate on B73 plants. However, females preferred FAW eggs laid on Tuxpeño plants, followed by those laid on B73‐lox10 and B73 plants. FAW neonate larvae parasitized by C. insularis preferentially colonized B73‐lox10 plants, although initially they colonized Tuxpeño and B73 plants, which were comparatively detrimental to the parasitoid's development. Overall, C. insularis females did not prefer parasitizing hosts on host plants on which their offspring's performance was highest. However, FAW larvae parasitized by C. insularis chose to colonize host plants on which the parasitoid's performance was highest. The results of this study provide information that could be useful for designing strategies for biological control of FAW.

  PublisherDOI

• Apanteles piceotrichosus Blanchard (Hymenoptera, Braconidae), first record from México, new molecular and biological data

  Journal of Hymenoptera Research · 2025-03-05

  articleOpen accessSenior author

  Between 1994 and 1995, Cotesia vestalis (Haliday 1834) (Hymenoptera, Braconidae) was introduced from the USA to Mexico to set up a biological control program for Plutella xylostella ; nevertheless, its field establishment was never confirmed. From 2020 to 2024, a braconid parasitoid on P. xylostella larvae was collected in broccoli in Guanajuato state, the main brassicas producer in Mexico. Those collections had initially been linked to the former releases, but this work corroborated that C. vestalis has not been recovered in Guanajuato, but rather an unidentified species of another braconid was confirmed. The objective of this work was to identify it with classical and molecular taxonomy, and to describe its basic biology under laboratory conditions. Morphological identification was performed using the descriptions of Blanchard (1994) and molecular analysis was performed using the 16S, 28S and COI markers. The parasitoid was identified as Apanteles piceotrichosus Blanchard, this species has been previously reported only from Argentina, Chile and Brazil, so it represents the first record for Mexico and its gene sequence is reported for the first time. A. piceotrichosus is a solitary koinobiont endoparasitoid of P. xylostella larvae. The egg is hymenopteriform with an incubation period of 0.92 d; larval and pupal stages lasted 5.86 ± 0.01 d, and 5.65 ± 0.02 d, respectively. Overall, there were 12.43 ± 0.01 d from egg to adult emergence. With honey availability, females and males lived 16.08 ± 0.19 and 17.58 ± 0.54 d, respectively.

  PublisherOA PDFDOI

• Tailoring Biopesticides: Amphiphile-Assisted Nanoprecipitation of Azadirachtin within a Glycine Matrix for Sustainable Agriculture, Enhanced Stability, and Larvicidal Efficacy against Fall Armyworm

  ACS Omega · 2025-08-19 · 3 citations

  articleOpen access

  The limited water solubility and environmental instability of natural pesticidal compounds impede their broader agricultural use.This study reports an amphiphile-assisted nanoprecipitation method to imbibe azadirachtin-rich neem seed extract (NSE) within a glycine carrier matrix, yielding a stable nanocomposite biopesticide.The formulation, prepared using polyoxyethylene sorbitan monooleate as a stabilizer and glycine as the matrix former, followed by lyophilization, exhibited a hydrodynamic diameter of 8 nm when redispersed in water.This glycine nanopesticide (GNP) significantly improved the photostability of azadirachtin under UV-AB irradiation (2000 W/cm 2 ); spectrophotometric analysis revealed a 27.7% reduction in photodegradation over a 4 day period compared to unformulated NSE powder demonstrated dialysis-based in vitro release assay showed sustained release, with 68.2 2.1% released over 7 days, fitting an exponential model with a time constant of 37.6 h.Contact bioassays against Spodoptera frugiperda larvae revealed enhanced larvicidal potency.LC 50 values showed a 1.5-to 6.6-fold improvement compared to unformulated NSE over 11 days.On day 7, GNP had an LC 50 of 0.13 mg/mL, compared to 0.86 mg/mL for NSE powder.The nanoformulation also improved wettability on tomato leaves, reducing the contact angle from 99.0 1.6(DI water) to 60at a concentration of 100 mg/mL GNP.This approach offers a practical method for improving the stability, delivery, and efficacy of hydrophobic biopesticides.

  PublisherOA PDFDOI

• Microbiome differentiation between micro-sympatric maize and teosinte reveals domestication-driven functional erosion of the microbiome across plant compartments

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-10-14

  preprintOpen accessSenior authorCorresponding

  Abstract Introduction Crop domestication has fundamentally transformed plant phenotypes through artificial selection, yet the consequences of domestication for plant-associated microbial communities across the plant-soil continuum remain poorly understood. Gap Statement While recent studies suggest that domestication impacts microbiome structures, the magnitude, mechanisms, and functional implications of such impacts have not been systematically quantified using controlled experimental designs that eliminate environmental confounding factors. Aim To characterize and quantify the effects of crop domestication on microbial community structure and function by comparing maize ( Zea mays subsp. mays ) and its wild ancestor Balsas teosinte ( Zea mays subsp. parviglumis ) across multiple plant compartments in an unmanipulated field setting in Mexico, maize’s domestication center. Methodology We applied a micro-sympatric design in a natural setting to compare microbial communities between maize and Balsas teosinte across five plant compartments: bulk soil, rhizosphere, mucilage, leaves, and seeds. Full-length 16S rRNA gene sequencing was used for taxonomic characterization, Functional Annotation of Prokaryotic Taxa (FAPROTAX) and PICRUSt 2.0 were used to predict functional profiles, and network analysis was used to assess functional connectivity. Results Compartment identity explained 72.2% of variation in community structure, with consistent host effects across all niches (9.0%). Teosinte maintained significantly higher microbial diversity than maize across all compartments, with pronounced differences in seeds (32.0 ± 1.9 vs 9.3 ± 1.8 species, P &lt; 0.01) and rhizosphere (60.3 ± 5.8 vs 33.8 ± 10.4 species, P &lt; 0.01). Eighty-nine percent of predicted metabolic functions showed significant changes associated with domestication, with teosinte exhibiting enhanced nitrogen fixation (0.89 ± 0.07 vs 0.44 ± 0.04 in maize mucilage), siderophore production, and pathogen suppression. Network analysis revealed functional fragmentation in maize, with reduced connections (80 to 49) and lower clustering coefficients (0.62 ± 0.03 vs 0.25 ± 0.02, P &lt; 0.001). Conclusion Balsas teosinte domestication fundamentally eroded microbial diversity and functional capacity in maize leading to a “domestication gap” that encompasses taxonomic loss, functional simplification, and network fragmentation, and replaced mutualistic plant-microbe partnerships with simplified microbial assemblages that may compromise crop resilience vis-à-vis a changing climate. Impact statement Understanding how plants select their microbial partners is crucial for enhancing agricultural productivity yet distinguishing between environmental and host genetic effects on microbiome assemblage remains challenging. Our study provides compelling evidence for host-driven microbiome assembly by comparing ancestral Balsas teosinte with derived maize growing in a common farm field in Mexico, eliminating environmental variation and experimental manipulation as confounding factors. By characterizing bacterial communities across different plant compartments, from soil to seed, we showed that each host’s genotype shaped divergent microbiome compositions despite growing in common environmental conditions. This research represents a significant step forward in understanding plant-microbe co-evolution during crop domestication and has three key implications. First, it suggests that microbiome traits were likely selected in conjunction with plant (host) traits during domestication and post-domestication selection. Second, it identifies specific bacterial communities that could be targeted for improving crop productivity and resilience. And third, it provides a methodological framework for studying host-microbe interactions in other crop-wild ancestor pairs. Our findings are particularly relevant for developing microbiome-based agricultural technologies and conservation strategies for beneficial plant-microbe interactions for deployment in traditional and modern farming systems. Data summary The authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.

  PublisherOA PDFDOI

• Unraveling genetic load dynamics during biological invasion: insights from two invasive insect species

  Peer Community Journal · 2025-04-02 · 4 citations

  articleOpen access

  Many invasive species undergo a significant reduction in genetic diversity, i.e. a genetic bottleneck, in the early stages of invasion. However, this reduction does not necessarily prevent them from achieving considerable ecological success and becoming highly efficient colonizers. Here we investigated the purge hypothesis, which suggests that demographic bottlenecks may facilitate conditions (e.g., increased homozygosity and inbreeding) under which natural selection can purge deleterious mutations, thereby reducing genetic load. We used a transcriptome-based exome capture protocol to identify thousands of SNPs in coding regions of native and invasive populations of two highly successful invasive insect species, the western corn rootworm (Chrysomelidae: Diabrotica virgifera virgifera ) and the harlequin ladybird (Coccinelidae: Harmonia axyridis ). We categorized and polarized SNPs to investigate changes in genetic load between invasive populations and their sources. Our results differed between species. In D. virgifera virgifera , although there was a general reduction in genetic diversity in invasive populations, including that associated with genetic load, we found no clear evidence for purging of genetic load, except marginally for highly deleterious mutations in one European population. Conversely, in H. axyridis , the reduction in genetic diversity was minimal, and we detected signs of genetic load fixation in invasive populations. These findings provide new insights into the evolution of genetic load during invasions, but do not offer a definitive answer to the purge hypothesis. Future research should include larger genomic datasets and a broader range of invasive species to further elucidate these dynamics.

  PublisherDOI

• Teosinte-derived SynCom and precision biofertilization modulate the maize microbiome, enhancing growth, yield, and soil functionality in a Mexican field

  Frontiers in Microbiology · 2025-04-09 · 8 citations

  articleOpen access

  Modern agriculture faces the challenge of optimizing fertilization practices while maintaining soil resilience and microbial diversity, both critical for sustainable crop production. We evaluated the effects of multiple fertilization strategies on soil microbial communities and plant performance, comparing conventional methods (urea-based and phosphorus fertilizers applied manually or via drone-assisted precision delivery) with biofertilization using a synthetic microbial consortium (SynCom) derived from teosinte-associated microbes. This SynCom consisted of seven bacterial strains: Serratia nematodiphila EDR2, Klebsiella variicola EChLG19, Bacillus thuringiensis EML22, Pantoea agglomerans EMH25, Bacillus thuringiensis EBG39, Serratia marcescens EPLG52, and Bacillus tropicus EPP72. High-throughput sequencing revealed significant shifts in bacterial and fungal communities across treatments. Untreated soils showed limited diversity, dominated by Enterobacteriaceae (&amp;gt;70%). Conventional fertilization gradually reduced Enterobacteriaceae while increasing Pseudomonas and Lysinibacillus populations. Drone-assisted conventional fertilization notably enhanced Acinetobacter and Rhizobiales growth. Biofertilization treatments produced the most pronounced shifts, reducing Enterobacteriaceae below 50% while significantly increasing beneficial taxa like Bacillus, Pantoea , and Serratia . Network analysis demonstrated that microbial interaction complexity increased across treatments, with Bacillus emerging as a keystone species. Drone-assisted biofertilization fostered particularly intricate microbial networks, enhancing synergistic relationships involved in nutrient cycling and biocontrol, though maintaining the stability of these complex interactions requires careful monitoring. Our findings provide key insights into how precision biofertilization with teosinte-derived microbial consortia can sustainably reshape the maize microbiome, improving crop performance and soil resilience.

  PublisherOA PDFDOI

Recent grants

• CAA: Domestication and Agronomic Selection Influences on Maize Defense Against a Specialist Herbivore

  NSF · $166k · 2008–2012

Frequent coauthors

• Raúl F. Medina

  Texas A&M University

  12 shared

• Michael V. Kolomiets

  Texas A&M University

  11 shared

• S. Bradleigh Vinson

  Texas A&M University

  10 shared

• Daniel Gonzalez‐Socoloske

  Andrews University

  10 shared

• Mamoudou Sétamou

  Texas A&M University – Kingsville

  9 shared

• Robert F. Luck

  Klinikum Chemnitz

  9 shared

• Andrea L. Joyce

  University of California, Merced

  8 shared

• Ana A. Fontes-Puebla

  Texas A&M University

  8 shared

Labs

• Department of Entomology, Texas A&M UniversityPI

Awards & honors

• Fulbright Scholar (2016-2017)
• President Sociedad Mexicana de Control Biológico (2015-2017)
• Global Faculty Advocate for Mexico, Texas A&M University (20…