Search Results (80)

Asian chestnut gall wasp (ACGW) (Dryocosmus kuriphilus Yasumatsu), native to China, is an invasive pest that causes significant economic losses in Castanea species. While some cultivars show full resistance by inhibiting insect development in buds, the underlying defense mechanisms remain unclear. In this study, the accumulation and distribution of hydrogen peroxide (H₂O₂) were investigated in dormant buds of chestnut cultivars that are resistant and susceptible to D. kuriphilus by using the 3,3′-diaminobenzidine (DAB) staining method. Buds were examined under a stereomicroscope during key stages of pest development, including oviposition, transition from egg to larva, gall induction, and gall development. Baseline levels of H₂O₂ were detected in all buds; however, these levels varied among cultivars, with resistant cultivars exhibiting lower basal levels. The degree of H₂O₂ accumulation was found to vary depending on plant–insect interaction, physiological processes, and cultivar-specific traits. Histochemical staining revealed that brown spots indicative of H₂O₂ accumulation were concentrated in the vascular bundles of leaf primordia and in the apical regions. In resistant hybrid cultivars, the defense response was activated at an earlier stage, while in resistant Castanea sativa Mill. cultivars, the response was delayed but more robust. Although consistently high levels of H₂O₂ were observed throughout the pest interaction in susceptible cultivars, gall development was not inhibited. During the onset of physiological bud break, increased H₂O₂ accumulation was observed across all cultivars. This increase was associated with endodormancy in susceptible cultivars and with both defense mechanisms and endodormancy processes in resistant cultivars. These findings highlight the significant role of H₂O₂ in plant defense responses, while also supporting its function as a multifunctional signaling molecule involved in gall development and the regulation of physiological processes. Full article

Symbiotic bacteria play a pivotal role in the biology and ecology of herbivorous insects, affecting host growth and adaptation. However, the effects of host identity on the symbiotic microbiota of gall-inducing insects remain less explored. In this study, we utilized high-throughput sequencing to investigate the effects of different oak hosts on the structure and diversity of the symbiotic microbial community in the asexual larvae of the gall-inducing wasp Trichagalma acutissimae. Host plant species significantly altered the alpha and beta diversity of symbiotic microbiota of T. acutissimae. At the phylum level, Proteobacteria was the predominant microflora in both groups, with significantly higher abundance in larvae parasitizing Quercus acutissima than in those parasitizing Q. variabilis. Pseudomonas, which has been identified as responsible for tannin decomposition, was the most dominant genus in T. acutissimae larvae infesting both hosts. LEfSe analysis revealed substantial differences in the symbiotic microbial communities between the two hosts while also highlighting some commonalities. Functional prediction analysis indicated no significant difference in the functional roles of symbiotic bacteria between larvae infesting the two hosts. These findings suggest that the symbiotic microbiome of T. acutissimae larvae is influenced by host plant species, yet different microbial compositions may perform similar functions, implying the potential role of symbiotic microbiota in the adaptation to high-tannin oak leaves. This research enhances our understanding of the symbiotic relationship between forest pests and their associated microbes. Full article

English oak (Quercus robur) hosts over 200 species of galls formed by insect larvae, most notably the oak gall wasp (Cynips quercusfolii). These galls result from the abnormal growth of plant tissue in response to oviposition, acting as a shelter and nutrient source for the larvae. In addition, the galls trigger oxidative stress in the host plant, resulting in the increased production of reactive oxygen species (ROS). This stress response promotes the biosynthesis of antioxidant compounds, including phenolic acids, flavonoids, and tannins. To our knowledge, this is the first study to monitor seasonal changes in phenolic acids, flavonoids, and tannins in relation to C. quercusfolii infestation over a complete vegetation cycle using integrated UPLC profiling and statistical modeling PCA. For the first time, the contents of phenolic acids, flavonoids, and tannins were assessed throughout the vegetation cycle—from flowering to acorn fall. Results showed that galls affect the biochemical profile of the whole plant, suggesting a systemic response to local infection. The results provide new insights into oak defense responses and suggest that gall formation may be associated with systemic metabolic shifts potentially involved in stress mitigation. Furthermore, the study supports the further investigation of oak galls as a valuable source of polyphenols for pharmacological and industrial applications. Full article

Plant-parasitic nematodes and insect pests critically threaten agricultural productivity, but chemical pesticides face limitations due to resistance and environmental concerns, necessitating eco-friendly biopesticides targeting both pests and nematodes. Here, we developed a high-throughput screening platform using Caenorhabditis elegans to identify entomopathogenic fungi exhibiting nematocidal activity against Meloidogyne incognita. Among 32 tested strains, nine Metarhizium spp. and one Beauveria strain demonstrated dual efficacy against C. elegans and M. incognita. Metarhizium anisopliae CQMa421 showed the highest virulence, suppressing nematode reproduction by 42.7% and inducing >80% mortality. Pot experiments revealed a 50% reduction in the root galling index and 50.3% fewer root galls in Solanum lycopersicum. The CQMa421 filtrate caused irreversible locomotor deficits and reduced egg hatching rates by 28%. Concurrently, intestinal damage, elevated oxidative stress and autophagy were observed in C. elegans. This was accompanied by a transcriptome-wide modulation of genes involved in detoxification and immune defense pathways. These findings demonstrate the efficacy of our C. elegans-based screening method for identifying fungi with nematocidal potential. CQMa421’s virulence against M. incognita suggests its promise for pest management, while molecular insights highlight pathways that may contribute to the future design of future nematicides. This study advances fungal biocontrol agents and offers a sustainable strategy for agriculture. Full article

Aprostocetus nitens Prinsloo & Kelly (Hymenoptera: Eulophidae) was identified as one of four hymenopteran ectoparasitoids utilizing three erythrina gall wasps, Quadrastichus bardus, Q. erythrinae, and Q. gallicola) (Hymenoptera: Eulophidae) in the native eastern Africa. In Hawaiʻi, the eurytomid wasp, Eurytoma erythrinae Gates & Delvare (Hymenoptera: Eurytomidae), was introduced and approved for statewide release in 2008 to control the erythrina gall wasp (EGW) Q. erythrinae Kim. EGW has devastated the wiliwili trees, Erythrina sandwicensis Degener (Fabaceae), an ecologically and culturally important native Hawaiian tree species. However, the parasitoid’s impact on the galled inflorescences and shoots was not adequate to ensure adequate seed set and maturation for successful tree recruitment. Aprostocetus nitens was thus evaluated as a prospective natural enemy to enhance the biological control of EGW to further protect the wiliwili trees in Hawaiʻi. Both choice and no-choice host specificity tests were conducted on seven non-target gall formers in the Hawaii Department of Agriculture, Insect Containment Facility, and showed that the parasitoid was extremely specific to EGW. The potential for competition between this parasitoid and the established E. erythrinae was also investigated, showing that the release of a second parasitoid will potentially complement the success of the eurytomid wasp for control of EGW. Unlike what was found in the native region, the Hawaiian laboratory colony is thelytokous, producing only female offspring. The life cycle took 20.1 ± 0.28 days under the laboratory conditions. Non-ovipositing female survived for 102.5 ± 2.9 days when fed honey and laid eggs for 25.1 ± 2.3 days with average fecundity of 156.7 ± 22.3 offspring/female. This value is 3.9-fold higher than offspring produced by E. erythrinae. Aprostocetus nitens, host specificity, competition with E. erythrinae, and its tri-trophic association with 15 Erythrina host plants and 5 gall wasp assemblages in the native African regions were defined. Implications to reduce frequent galls on the native Erythrina plants and likely domination over E. erythrinae, are discussed. Full article

Analyzing the nutritional and defensive chemistry of Quercus rugosa provides insight into gall wasp interactions. Quercus rugosa is the most widely distributed white oak species in Mexico. It is the dominant canopy species in its geographic distribution range and has the largest number of associated gall wasp species (Cynipidae: Cynipini). Our main aims were to characterize the nutritional and defensive chemistry of Q. rugosa leaves and determine whether this chemistry differed between leaves with and without galls. We evaluated 60 trees from six populations of Q. rugosa in central Mexico. For each tree, we analyzed the nutritional chemistry (nitrogen, phosphorus, carbon, and carbon/nitrogen ratio) and defensive chemistry (secondary metabolites). Also, we characterized the community of cynipids in the leaf tissue of each tree. We documented 18 cynipid species, and the cynipid communities differed in composition among localities. We recorded the presence of a total of ten phenolics. The composition of nutritional and defensive chemicals differed significantly between leaves with and without galls in each locality. The nutritional and defensive chemical compounds of Q. rugosa were influenced by their associated cynipids. Our results suggest that gall-inducing cynipids influence the production of secondary metabolites in leaves with galls through the reassignment of nutritional compounds by the hosts. Full article

Ficus trees (Moraceae) play a vital role in sustaining the stability of tropical and subtropical rainforests. The obligate mutualism between Ficus species and their pollinating fig wasps renders them an exemplary model for investigating insect–plant coevolution. In this study, we employed Ficus hispida Linn. f., an ecologically significant fig species in tropical rainforests, to conduct a wasp-introduction controlled experiment in the field. This method enabled us to precisely delineate the developmental stages of figs. We collected samples at specific intervals and examined the impact of pollinating fig wasp entry on the hormonal metabolism of male and female figs using liquid chromatography–tandem mass spectrometry analysis. The findings demonstrate that pollinator entry significantly decreases fig abscission. Moreover, it substantially altered the developmental indices of the figs. Unpollinated figs exhibit elevated levels of abscisic acid (ABA), which increases the likelihood of fig abortion and reduces the probability of pollinator entry into senescent figs. Following pollinator entry, indole-3-acetic acid (IAA) levels rise in both male and female figs. Male figs show higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC), jasmonic acid (JA), and salicylic acid (SA), whereas these changes are less pronounced in female figs. Additionally, pollinated male figs display increased levels of cytokinins (CKs) and other hormones compared to female figs, suggesting a coordinated hormonal response to the stress induced by pollinator oviposition and gall development. Our findings suggest that the entry of pollinators likely triggers the transition from the female to the interfloral phase, with hormonal regulation playing a crucial role in the reproductive dimorphism of figs. This research can offer novel insights into the mechanisms underlying fig–wasp mutualism. Full article

The structural and ultrastructural characteristics of galls induced by three species of insects parasitizing on oak leaves (Quercus robur L.) were examined utilizing light and fluorescent microscopes, as well as scanning and transmission electron microscopes. The tissues of the investigated galls exhibited marked differences from those of a typical oak leaf. In the Cynips quercusfolii L. gall, the larval chamber in its final stage was formed from the remnants of dead cells that remained after larval feeding on the gall nutritive tissue. The cells of the gall nutritive tissue and the cells of the gall parenchyma exhibited diametrical differences: the former contained dense cytoplasm and had large nuclei and nucleoli, whereas the latter displayed sparse cytoplasm, prominent vacuoles, and very small nuclei. The region of coalescence between the gall stalk and leaf tissues has been described. In Neuroterus numismalis Geoffroy gall, the early developmental phases have been described in detail. The external gall tissues resembled periderm, whereas periderm does not normally occur in leaves. In the cytoplasm of Cynips longiventris Hartig gall, different bodies were found, including organized smooth endoplasmic reticulum; however, not all of the observed structures were definitively classified. Full article

The leaf is a critical organ for assimilation in plants, and the anatomical structure of the leaf can reflect the adaptability of plants to their environment to a certain extent. The research objects in this investigation were 36 different cultivars (lines) of goji germplasm resources. The structure and stoma condition of healthy leaves were the subject of a comparative investigation. Significant variations in leaf structural indices and stoma were identified among various goji cultivars (lines). The leaves of goji were the thickest and possessed the lowest stoma density. The resilience of goji germplasm resources was assessed using the main component analysis approach and the membership function. The results showed that LR (L. ruthenicum Murr.) and LCy (L. cylindricum Kuang) exhibited the strongest resistance. Goji resistance is significantly influenced by thickness of the upper cuticle (TUC) and thickness of the lower cuticle (TLC), according to the analytical results for several leaf anatomical indicators and stress resistance. By analyzing the wax content of 13 different goji cultivars (lines) and field infection results, it was found that Tianjing 3 had the highest wax content, the smallest average number of galls, and the smallest infection area. This suggests that Tianjing 3 has the strongest resistance to Aceria pallida, and that its insect resistance is correlated with its wax content. This study offers a thorough assessment of 36 goji germplasm resources’ resilience, providing a point of reference for the selection and propagation of resistant cultivars within these resources. Full article

Silicon (Si) is a widely recognized element in plant defense, often enhancing resistance to herbivory by strengthening cell walls and deterring feeding by external herbivores. However, its impact on internal, endophytic herbivores, such as gall-inducing insects, remains underexplored. This study investigates the role of silicon in Bauhinia brevipes, focusing on its effects on herbivory by insects. We hypothesize that while silicon strengthens plant tissues and reduces feeding by external herbivores, it may have a limited effect on internal feeders, such as gall-inducing insects. Our results indicate that silicon accumulation in leaves significantly reduces herbivory by chewing insects but has no direct effect on the occurrence of gall-inducing insects. Silicon content in galled tissues was lower compared to healthy leaves, suggesting that gall-inducing insects may manipulate silicon distribution to mitigate its defensive effects. Our results indicate that hypersensitivity reactions were positively influenced by silicon, highlighting the role of this element in enhancing localized defense mechanisms. Our findings reveal silicon’s tissue-specific roles in plant defense, emphasizing the need for more research on its nuanced interactions with endophytic herbivores and implications for ecological applications. This research contributes to the literature on silicon’s multifaceted role in plant–herbivore interactions and its potential applications in sustainable pest management. Full article

In the complex dynamics of plant–insect interactions, the specialized galling of reproductive structures presents unique evolutionary adaptations. This study investigates the parasitic relationship between Arastichus gallicola (Hymenoptera, Eulophidae), an ovary-galling wasp, and the inflorescences of Thaumatophyllum bipinnatifidum (Araceae). We employed field experiments and histological analyses to investigate the mechanisms driving this interaction. We reveal that ovule fertilization is not required for gall formation; however, pollination substantially enhances gall retention by reducing inflorescence abscission. Inflorescences exposed solely to galling presented a 64% abscission rate, whereas those with both galling and pollination experienced 33% abscission, underscoring pollination’s role in mitigating inflorescence loss. Detailed observations of A. gallicola oviposition and larval development reveal the intricate gall formation process characterized by progressive tissue hypertrophy surrounding the larva. Galling and seed development were mutually exclusive, with only 9% of fruits containing both. This mutual exclusivity suggests a competitive interaction for developmental resources within the ovary. Our findings underscore the specialized larval biology of galling chalcid wasps, illustrating how interactions between gall formation and host reproductive strategies shape the evolution of gall induction in floral tissues. Our study advances the understanding of ovary-galling adaptations and the selective pressures shaping antagonistic and mutualistic interactions in plant reproductive structures. Full article

Increasing temperatures, prolonged drought, the increased severity and intensity of storms, and other effects of climate change are being felt globally, and long-lived forest tree species may struggle in their current ranges. Oaks (Quercus spp.) have evolved a range of adaptations to dry and hot conditions and are believed to be a “climate change winner” by increasing their suitable habitat. However, a mixture of life history traits and increasing susceptibility to herbivores and xylovores as well as secondary pathogen infections still put oaks at risk of decline. Oak species found in the Midwestern, Great Lakes, and Northeastern United States and Canada are important keystone species with high ecological and economical importance. They are also vulnerable to existing, new, and emerging threats that have the potential to cause mortality across entire stands quickly. Current examples of insect threats include the Lymantria dispar (spongy moth), Agrilus bilineatus (twolined chestnut borer), and Nitidulidae (sap beetles) as disease vectors. Examples of emerging insects of concern include Cynipidae (oak gall wasps) and Enaphalodes rufulus (red oak borer). This study describes these insects, explains their mechanisms of action and the effects on oaks, and explores mitigation strategies for each. Full article

Carotenoids are common and diverse organic compounds with various functional roles in animals. Except for certain aphids, mites, and gall midges, all animals only acquire necessary carotenoids through their diet. The house fly (Musca domestica) is a cosmopolitan pest insect that populates diverse habitats. Its larvae feed on organic substrates that may vary in carotenoid composition according to their specific content. We hypothesized that the carotenoid composition in the adult house fly’s body would reflect the carotenoid composition in the larval feed. House fly larvae were reared on diets that differed in carotenoid composition. HPLC analysis of the emerging adult flies indicate that the carotenoid composition of adult house flies is related, but not identical, to the carotenoid composition in its natal substrate. These findings may be developed to help identify potential sources of house fly infestations. Also, it is recommended that rearing substrates of house fly larvae, used for animal feed, should be carefully considered. Full article

Overwintering survival by insects, whether of the freeze-tolerant or freeze-avoiding types, is typically associated with a strong suppression of metabolic rate (e.g., entry into diapause) that involves the differential expression of many genes with regulation at the transcriptional, translational or post-translational levels. Epigenetic modifications have been suggested to play a vital role in regulating cold responses of insects. However, knowledge of the roles of epigenetic mechanisms in modulating gene expression for winter survival of the larvae of two goldenrod gall formers, the freeze-tolerant dipteran Eurosta solidaginis and the freeze-avoiding lepidopteran Epiblema scudderiana, remain unknown. The current study evaluates the role of cold-induced lysine methylation and histone modifications, with enzymes of lysine methylation (SETD8, SETD7, SUV39H1, SMYD2 and ASH2L), as well as relative levels of histone H3 acetylation (H3K9ac, H3K18ac, H3K27ac, H3K56ac) and methylation (H3K4me1, H3K9me3, H3K36me2) examined in two insects. Significant (p < 0.05) reductions were observed in most of the targets of histone methylation/acetylation for decreasing temperatures of Ep. scudderiana larvae, whereas selected histone methylation/acetylation targets were conversely elevated (p < 0.05) in E. solidaginis, particularly under conditions of 5 °C for 4 h. Histone H3 expression was found to be variable without statistical differences in larval goldenrod gall moths and gall flies. These results provide basic information on the patterns of epigenetic regulation involved in insect cold hardiness. Full article

The cross-hybridization of American chestnut (Castanea dentata (Marsh.) Borkh.) with Chinese chestnut (Castanea mollissima Bl.) is a promising strategy for restoring a blight-resistant strain of this keystone species to the Appalachian mountains. To assess the ecological impacts of hybridization on invertebrate communities, we conducted a study across chestnut plots with varying degrees of hybridization (75%, 94%, or 100% American chestnut). Our findings indicate American chestnut hybridization impacted invertebrate communities above- and belowground. Aboveground insect community composition, insect herbivory, gall infestation, and belowground invertebrate diversity were all altered. While some of these differences could be explained by different growth habits or environmental differences, stark differences in Asian chestnut gall wasp infestation (Dryocosmus kuriphilus Yasumatsu.) suggest a genetic component. These results suggest that chestnut hybridization, and particularly expanded restoration efforts using chestnut hybrids, could impact invertebrate communities above- and belowground in addition to pest dynamics. Understanding these effects is crucial for successful chestnut restoration and ecosystem management. Full article