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ABSTRACT During the early stages of local adaptation and speciation, genetic differences tend to accumulate at certain regions of the genome leading to the formation of genomic islands of divergence (GIDs). This pattern may be due to selection and/or difference in the rate of recombination. Here, we investigate the possible causes of GIDs in Drosophila yakuba mayottensis, and reconfirm using field collection its association with toxic noni (Morinda citrifolia) fruits on the Mayotte island. Population genomics revealed lack of genetic structure on the island and identified 23 GIDs distinguishing D. y. mayottensis from generalist mainland populations of D. y. yakuba. The GIDs were enriched with gene families involved in the metabolism of lipids, sugars, peptides and xenobiotics, suggesting a role in host shift. We assembled a new genome for D. y. mayottensis and identified five novel chromosomal inversions. Twenty one GIDs (~99% of outlier windows) fell in low recombining regions or subspecies‐specific inversions. However, only two GIDs were in collinear, normally recombining regions suggesting a signal of hard selective sweeps. Unlike D. y. mayottensis, D. sechellia, the only other noni‐specialist, is known to be homosequential with its generalist relatives. Thus, whereas structural variation may disproportionally shape GIDs in some species, striking parallel adaptations can occur between species despite distinct genomic architectures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Dead-end trap crops are plants used in pest management that are highly attractive to egg-laying adults but do not support the survival of the developing offspring. For the diamondback moth (DBM; Plutella xylostella), Barbarea vulgaris and B. verna (upland cress) are proven dead-end trap crops but the evidence for Lepidium sativum has been contradictory with one study claiming dead-end effects but others showing that it is a suitable host. Since glucosinolate and saponin levels, which, respectively, stimulate oviposition and act as deterrents, vary with plant age in Barbarea spp., the goal of the present study was to investigate the effects of plant age on the attractiveness and dead-end properties of upland cress and two cultivars of L. sativum (garden cress and broadleaf cress). When given the opportunity to lay eggs on the putative dead-end trap crops or cabbage (Brassica oleracea), DBM did not preferentially lay eggs on garden cress and upland cress until the plants were 5 weeks or older, while broadleaf cress was attractive at all ages. Egg-to-adult survival and growth rate on garden cress and broadleaf cress was as high or higher as on cabbage, regardless of plant age. Upland cress did not reduce survival of DBM at 2 and 5 weeks old but did at 10 weeks old. We confirm that plant age is critical to the effectiveness of upland cress as a dead-end trap crop and conclude that garden cress and broadleaf cress can be suitable trap crops but exhibit no dead-end properties. [ABSTRACT FROM AUTHOR]

Brassicaceous plants are attacked by a wealth of specialist herbivores that include the Diamondback moth (DBM) Plutella xylostella L. (Lepidoptera: Plutellidae), control of which requires novel biocontrol strategies. DBM is a cosmopolitan pest causing damage that varies yearly in Finland depending on the timing and extent of their migration. Intercropping with companion plants can hamper host location by herbivores or attract their natural enemies. We tested two sustainable companion plant-based protection strategies on field-grown broccoli (Brassica oleracea var. italica), which comprised 1) aromatic and repellent-releasing Rhododendron tomentosum (RT) (bottom-up strategy), and 2) nectar-producing buckwheat Fagopyrum esculentum (FE) (top-down strategy) combined with an early-season floating row cover (mechanical control) (MC + FE). In addition, a control (no companion plant or cover) and mechanical control (MC) without FE were included. DBM adults on yellow sticky traps and larvae on plants were counted, and feeding damage on leaves was quantified. Volatile organic compounds emitted by broccoli plants in control and RT plots, and emitted by boundary RT plants in RT plots, were identified and quantified. There was a mass outbreak of DBM in early summer with a population peak in mid-July when the second adult generation emerged. DBM adult densities were significantly lower in RT and MC + FE than in control plots. Broccoli in RT plots had a lower larval density and lower damage intensity than in control plots in the early-season. Larval densities and damage intensities were the highest in the latter half of July. Control plots had the highest number of larvae followed by RT, MC, and MC + FE plots. Damage intensities in control plots were significantly higher than in all other treatments throughout the season. Damage intensity was lower in MC and MC + FE plots than in RT plots at the end-of-July. R. tomentosum emitted two characteristic sesquiterpene alcohols, palustrol and ledol, but no evidence of adsorption and re-release of these compounds from Brassica plants grown in RT plots was found. We conclude that incorporating RT as a boundary plant and using a mechanical row cover reduces DBM damage on broccoli, but further multi-year trials under varying degrees of pest pressure are needed. [ABSTRACT FROM AUTHOR]

Insect herbivory plays a crucial role in shaping plant communities in many terrestrial ecosystems. However, in African savannas, insect herbivory has been relatively understudied compared to large mammalian herbivory. In this study, we examined the impact of insect herbivory, focusing on leaf chewers and miners, in a South African savanna‐forest mosaic (including patches of forest, thicket and savanna) in Hluhluwe iMfolozi Park, South Africa. Our investigation spanned gradients of rainfall, fire frequency and mammal density. We surveyed a total of 864 woody plants from 48 plant species in 38 plots. Insects consumed 6% of leaf biomass, which is comparable to their impact in temperate broadleaf forests, but the extent of herbivory damage varied between vegetation types. Overall, leaf loss was 70% higher in forests and savanna than that in thicket. Plants in the forests experienced greater damage from chewing insects, whereas miners caused relatively more damage in savannas. Rates of insect herbivory also varied among plant species, declining with carbon and dry matter content but increasing with specific leaf area. Although no significant trade‐off was detected between insect and mammal herbivory, plant species with limited physical defences against mammals tended to experience high levels of insect herbivory. Our findings highlight the intricate dynamics of insect herbivory in different vegetation types and suggest that insect leaf herbivory, alongside mammalian herbivory, could play a significant role in influencing plant community composition and overall savanna ecosystem functioning. [ABSTRACT FROM AUTHOR]

Simple Summary: This study explores whether the winter-active insect, Boreus hyemalis, shows a non-random distribution among different moss species in its natural habitats and in the laboratory. In field surveys, B. hyemalis was found on 21 moss species, but showed a particular association with Dicranella heteromalla and Hypnum cupressiforme. In laboratory tests, Polytrichum formosum was the most frequently selected species. Although some discrepancies between field and lab results were noted, our findings suggest that B. hyemalis does not associate with mosses randomly, but tends to select certain species. This research helps us understand how these insects interact with their mossy environments. Our understanding of herbivorous insect's host selection is often based on observed associations with host plants, which can be biased by relative plant abundance, leading to inaccurate assumptions of preference. These biases may be particularly pronounced for insects associated with bryophytes, where dominance patterns are less evident. Estimating selection tendencies is also challenging for rare species with unique ecologies. Boreus hyemalis, a winter-active insect, associates with a range of bryophyte species, yet its specificity in moss-host selection remains unclear. This study investigates whether B. hyemalis shows non-random distribution among bryophyte species in natural habitats and laboratory settings. Field surveys revealed associations with 21 moss species, with significant selection tendencies toward Dicranella heteromalla and Hypnum cupressiforme, with moss species richness being a key factor for boreid inhabitance. Laboratory tests assessed selection among 14 moss species, including H. cupressiforme morphotypes, under controlled conditions. Results indicated Polytrichum formosum was the most frequently selected in the lab. Despite some discrepancies between field and lab findings, B. hyemalis shows specific selection tendencies for particular moss species. These results provide new insights into the ecological interactions between bryophytes and this winter-active insect, emphasizing the importance of moss structure and species richness in shaping B. hyemalis distribution. [ABSTRACT FROM AUTHOR]

Aiming to assess the role of leaf waxy cuticle and its chemical composition on citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae) larval feeding, six citrus cultivars were selected. Our findings showed that the larval density was higher at 59.5% on Mayer lime followed by 53.6% on Kinnow and the least activity of CLM was found (19.3-38.4%) on Musambi. The cuticular wax layer was found greater (67.6 µg/cm2) in Tangerine (Fairchild) followed by 59.6 µg/cm2 in Succari and 56.0 µg/cm2 in Musambi. The results showed that the epicuticular wax layer had negative and significant (P < 0.05) relation with the larval density. Other chemical compounds; aldehyde, alcohol, fatty acid, and hydrocarbon showed non-significant relation with the CLM larval density. Multiple regression analysis showed a 33.5% role of epicuticular wax with CLM larval density. The cultivars such as Succari and Musambi with a greater amount of leaf wax showed a lower density of CLM larvae. The study provides important information on wax related compounds involved in citrus-CLM interaction, which can help in developing an efficient control strategy for this destructive pest. [ABSTRACT FROM AUTHOR]

Insects are the major pollination vectors for angiosperms, and insects native to a given habitat can play an irreplaceable ecological role in food webs and plant reproduction. With precipitous declines in insect species over the last decades, it is urgent to document insect assemblages in native plant communities to support conservation efforts. Identifying pollinators and their pollination activity is challenging; however, emerging technological methods are providing new monitoring capabilities. In this study, we compare the accuracy of two different methods of monitoring to assess the flower‐visiting insect assemblage and likely pollinators of Encinitas baccharis (Baccharis vanessae): focal observations and video recordings from camera traps. B. vanessae is a rare, endemic species found in Coastal Sage Scrub communities in San Diego County. This federally listed species is threatened by habitat loss and fragmentation, which may also be affecting the availability of its insect pollinators. Results indicate that B. vanessae supports and is supported by a variety of flower‐visiting insect groups. The diversity of insect visitors at male and female plants were similar across all diversity measurements. The insect vectors identified were as expected given B. vanessae pollination syndrome. This syndrome also aligns with wind as a pollination vector, providing evidence of ambophily. While focal observations underreported insect activity by approximately half, the proportions of common diurnal visitors were similar with both methods. Camera traps were unable to provide sufficient detail to discern visually similar groups, but were able to record nocturnal insect activity, which was dominated by moths (Lepidoptera, 82%). While collection protocol in this study did not record the time an insect spent interacting with a flower, we anecdotally observed moths spent notably longer periods in contact with flowers than most diurnal insects. This study has implications for effective monitoring and conservation of endangered plant species and their affiliated pollinators. [ABSTRACT FROM AUTHOR]

Onion thrips (Thrips tabaci) are a major pest of onion crops, but they can be controlled using syrphid larvae, which are omnivorous, as biological control agents. The introduction of secondary plants may enhance syrphid activity and contribute to the suppression of onion thrips population in onion–barley intercropped fields. Therefore, two experiments were conducted to evaluate the effect of introducing secondary plants on the population of onion thrips and the occurrence of syrphids in onion–barley intercropped fields. In the first 2-year experiment, buckwheat, lacy phacelia, and coriander planted around barley-intercropped onion fields did not result in a significant reduction in the number of onion thrips. However, in the second experiment, which employed mixed intercropping of barley and buckwheat, significantly greater suppression of onion thrips population was observed in the mixed intercropping plots than in plots containing only barley intercropping. In addition, the number of syrphid eggs on intercropped barley was significantly higher in the mixed intercropping plots than in plots containing barley alone, demonstrating that planting flowering plants near barley can attract hoverflies and increase oviposition on barley. Furthermore, three-year experiments revealed more syrphid larvae on onion plants than on barley, with eggs found only on barley. These findings indicate that hoverflies oviposit on intercropped barley; then, the hatched larvae move to onion plants to prey on onion thrips. Overall, this study offers great insights into the potential use of intercropping with flowering plants to boost natural biological control of onion thrips, providing implications for sustainable pest management in onion production. [ABSTRACT FROM AUTHOR]

Rosalia funebris (RFUNE; Cerambycidae), the banded alder borer, is a longhorn beetle whose larvae feed on the wood of various economically and ecologically significant trees in western North America. Adults are short-lived and not known to consume plant material substantially. We sequenced, assembled, and annotated the RFUNE genome using HiFi and RNASeq data. We documented genome architecture and gene content, focusing on genes putatively involved in plant feeding (phytophagy). Comparisons were made to the well-studied genome of the Asian longhorned beetle (AGLAB; Anoplophora glabripennis) and other Cerambycidae. The 814 Mb RFUNE genome assembly was distributed across 42 contigs, with an N50 of 30.18 Mb. Repetitive sequences comprised 60.27% of the genome, and 99.0% of expected single-copy orthologous genes were fully assembled. We identified 12,657 genes, fewer than in the four other species studied, and 46.4% fewer than for Aromia moschata (same subfamily as RFUNE). Of the 7,258 orthogroups shared between RFUNE and AGLAB, 1,461 had more copies in AGLAB and 1,023 had more copies in RFUNE. We identified 240 genes in RFUNE that putatively arose via horizontal transfer events. The RFUNE genome encoded substantially fewer putative plant cell wall degrading enzymes than AGLAB, which may relate to the longer-lived plant-feeding adults of the latter species. The RFUNE genome provides new insights into cerambycid genome architecture and gene content and provides a new vantage point from which to study the evolution and genomic basis of phytophagy in beetles. [ABSTRACT FROM AUTHOR]

Aphids are among the most economically significant pests in cereal crops worldwide. Despite high interest in the natural control of aphids by applying natural enemies, intercropping and companion planting, the concurrent effects of the combinations of these methods due to their synergistic or antagonistic interactions remain largely unknown for both aphids and their host crops. Here we identify the relative effectiveness of simultaneous bottom–up and top–down factors in controlling one of the most economically important species of cereal aphids, the bird cherry‐oat aphid Rhopalosiphum padi L. For this, we conducted microcosm experiments using a full‐factorial design of three aphid‐control treatments including predator presence (i.e., lacewing larvae of Chrysoperla carnea), host‐plant intercropping (i.e., barley alone vs barley in combination with wheat and rye) and companion planting with an aphid‐repellent plant (garlic), and estimated their direct, indirect and interactive effects on aphid density. Our results show strong simultaneous top–down control of the aphid population by predation and bottom–up control by both host‐plant biomass and companion planting with garlic. The use of garlic as a companion plant for cereal crops in our study neither altered crop biomass nor suppressed the efficiency of aphid predator. Our findings suggest that the simultaneous application of aphid predator and companion planting with garlic holds promise as a potential strategy for the natural control of cereal aphid populations on grain crops, without generating related agroecosystem disservices, such as loss in crop production and deterioration of the natural enemies of pests. However, given the controlled lab conditions and limited timeframe of our study, further research is needed to confirm its effectiveness in field conditions to ensure its broader applicability in sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Abstract Spatio-temporal variation in the quantity and quality of resources available to insects influence the strength and direction of interactions with plants, ultimately affecting the preference of insects and also plant performance. Florivory encompasses the consumption of floral resources and has both direct and indirect effects on plant reproduction and performance. In this study, we evaluated how synchronic flowering of phylogenetic-related plant species blooming in an urban landscape affected insect florivores. Flowers from six plant species belonging to the Bignoniaceae family were sampled and florivory was measured as the frequency of attacked flowers (florivory incidence) as well as the amount of floral area removed (florivory intensity). We detected species-specific variation in florivory incidence and intensity in the urban landscape and our spatial analysis indicated that plants that were close (< 200 m apart) and in simultaneous blooming had significantly correlated levels of florivory than plants that were far apart (almost 1 km). Our data indicates complex relationships between insects and flowers and we suggest that a throughout evaluation of insect community and dispersal ability is necessary to understand the patterns of florivory in trees, as well as its effects on plant reproduction and insect attraction.

Abstract Economic losses from insect herbivory in agroecosystems has driven the development of integrated pest management strategies that reduce pest incidence and damage; however, traditional chemicals-based control is either being complemented or substituted with sustainable and integrated methods. Major sustainable pest management strategies revolve around improving host plant resistance, and one of these traits of interest is Brown midrib (BMR). Originally developed to increase nutritional value and ease of digestion for animal agriculture, BMR is a recessive plant gene usually found in annual grasses, including sorghum and sorghum-sudangrass hybrids. In sorghum-sudangrass, BMR expressed plants have lower amounts of lignin, which produces a less fibrous, more digestible crop, with possible implications for plant defense against herbivores- an area currently unexplored. Fall Armyworm (FAW; Spodoptera frugiperda) is a ruinous pest posing immense threat for sorghum producers by severely defoliating crops and being present in every plant stage. Using FAW, we tested the effect of seed treatment, BMR, and plant age on FAW growth, development, and plant defense responses in sorghum-sudangrass. Our results show that seed treatment did not affect growth or development, or herbivory. However, presence of BMR significantly reduced pupal mass relative to its non-BMR counterpart, alongside a significant reduction in adult mass. We also found that plant age was a major factor as FAW gained significantly less mass, had longer pupation times, and had lower pupal mass on the oldest plant stage explored, 60-days, compared to younger plants. These findings collectively show that pest management strategies should consider plant age, and that the effects of BMR on plant defenses should also be studied.

Insect attachment devices enhance adhesion to complex-geometry substrates by increasing the real contact area. In nature, insects mainly interact with plant surfaces that are often covered by 3D wax structures. Here, we describe, discuss, and give a mechanical interpretation of plant waxes and the possible fracture mechanisms of these wax structures during their interactions with the adhesive pads of insects. It is argued that these plant surface microstructures significantly influence insect adhesion through reducing the contact area and contaminating the insect pads. [ABSTRACT FROM AUTHOR]

Actilasioptera gagné (Diptera: Cecidomyiidae) is a gall inducer associated with the gray mangrove, Avicennia marina (Acanthaceae) which hasn't been previously recorded in Egypt. Mangrove forests are unique functional ecosystems having much social, ecological, economic and biological importance. This work aimed to study the relationship between the gall marker Actilasioptera Gagné and the gray mangrove, Avicennia marina, in addition to evaluating the quantifications of phytochemical and proximate compositions of Avicennia marina leaves with galls and without galls, as well as their antinutrients compositions on the Red Sea coast. The results of phytochemical compositions showed that total flavonoids, flavonols, steroids, saponins, tannins, alkaloids, and total phenolic contents were statistically significant at P< 0.05 and higher in Avicennia marina leaves with galls than without galls. The total flavonoids, flavonols, and phenolic acids in the Avicennia marina leaves with galls and leaves without galls were 181.93± 1.36mg RTE/ g DW, 51.10± 0.56mg RTE/ g DW, 20.27± 0.65mg RTE/ g DW, 8.77± 0.51mg RTE/ g DW, 70.42± 0.61mg GAE/ g DW, and 26.90± 1.25mg GAE/ g DW, respectively. In addition, total steroids, saponins, tannins, and alkaloids were significantly higher in the Avicennia marina leaves with galls than in leaves without galls. The high values of proximate contents were found in Avicennia marina leaves with galls than Avicennia marina leaves without galls. Furthermore, the highest levels of anti-nutrients were found in Avicennia marina leaves with galls: oxalates, phytates, and cyanogenic glycosides were 21.60± 0.52mg/ 100g, 1.102± 0.08mg/ 100g, and 6.98± 0.22mg/ 100g, respectively. Actilasioptera Gagné can infest and damage mangrove plant leaf, leading to the death of the plant leaf as a result of access of plant defense chemicals against insect pests. [ABSTRACT FROM AUTHOR]

Honeydew, a sugary excretion produced by sap‐feeding insects, plays a pivotal role in shaping intricate interactions between insects and plants. This review explains the multifaceted aspects of honeydew, beginning with an overview of its production mechanisms and factors influencing its variability across insect species and plant hosts. Exploring its composition, we examine the chemical components and nutritional aspects, highlighting variations based on insect species and plant sources. The impact of honeydew on microbial communities is explored, shedding light on its role in influencing the diversity and abundance of microorganisms. Furthermore, the review investigates how honeydew affects pest behaviour and population dynamics, elucidating plant responses to honeydew deposition. In the realm of biocontrol, we examine the intricate relationships between honeydew and natural enemies, considering potential implications for integrated pest management. Beyond these individual components, the paper discusses the broader ecological consequences of honeydew in ecosystems, emphasizing the interconnected relationships between insects, plants and microorganisms. The review concludes by identifying research gaps and suggesting future directions, recognizing the need for further investigation into areas with potential applications for agriculture and ecology. This review provides a comprehensive synthesis of the current understanding of honeydew's significance in insect–plant interactions, offering insights for both researchers and practitioners in the field. [ABSTRACT FROM AUTHOR]

Economic losses from insect herbivory in agroecosystems has driven the development of integrated pest management strategies that reduce pest incidence and damage; however, traditional chemicals-based control is either being complemented or substituted with sustainable and integrated methods. Major sustainable pest management strategies revolve around improving host plant resistance, and one of these traits of interest is Brown midrib (BMR). Originally developed to increase nutritional value and ease of digestion for animal agriculture, BMR is a recessive plant gene usually found in annual grasses, including sorghum and sorghum-sudangrass hybrids. In sorghum-sudangrass, BMR expressed plants have lower amounts of lignin, which produces a less fibrous, more digestible crop, with possible implications for plant defense against herbivores- an area currently unexplored. Fall Armyworm (FAW; Spodoptera frugiperda) is a ruinous pest posing immense threat for sorghum producers by severely defoliating crops and being present in every plant stage. Using FAW, we tested the effect of seed treatment, BMR, and plant age on FAW growth, development, and plant defense responses in sorghum-sudangrass. Our results show that seed treatment did not affect growth or development, or herbivory. However, presence of BMR significantly reduced pupal mass relative to its non-BMR counterpart, alongside a significant reduction in adult mass. We also found that plant age was a major factor as FAW gained significantly less mass, had longer pupation times, and had lower pupal mass on the oldest plant stage explored, 60-days, compared to younger plants. These findings collectively show that pest management strategies should consider plant age, and that the effects of BMR on plant defenses should also be studied. [ABSTRACT FROM AUTHOR]

Bemisia tabaci (whitefly) is a polyphagous agroeconomic pest species complex. Two members of this species complex, Mediterranean (MED) and Middle-East-Asia Minor 1 (MEAM1), have a worldwide distribution and have been shown to manipulate plant defenses through effectors. In this study, we used three different strategies to identify three MEAM1 proteins that can act as effectors. Effector B1 was identified using a bioinformatics-driven effector-mining strategy, whereas effectors S1 and P1 were identified in the saliva of whiteflies collected from artificial diet and in phloem exudate of tomato on which nymphs were feeding, respectively. These three effectors were B. tabaci specific and able to increase whitefly fecundity when transiently expressed in tobacco plants (Nicotiana tabacum). Moreover, they reduced growth of Pseudomonas syringae pv. tabaci in Nicotiana benthamiana. All three effectors changed gene expression in planta, and B1 and S1 also changed phytohormone levels. Gene ontology and KEGG pathway enrichment analysis pinpointed plant–pathogen interaction and photosynthesis as the main enriched pathways for all three effectors. Our data thus show the discovery and validation of three new B. tabaci MEAM1 effectors that increase whitefly fecundity and modulate plant immunity. [Graphic: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Phloem-feeding insects include many important agricultural pests that cause crop damage globally, either through feeding-related damage or upon transmission of viruses and microbes that cause plant diseases. With genetic crop resistances being limited to most of these pests, control relies on insecticides, which are costly and damaging to the environment and to which insects can develop resistance. Like other plant parasites, phloem-feeding insects deliver effectors inside their host plants to promote susceptibility, most likely by a combination of suppressing immunity and promoting nutrient availability. The recent emergence of the effector paradigm in plant–insect interactions is highlighted by increasing availability of effector repertoires for a range of species and a broadening of our knowledge concerning effector functions. Here, we focus on recent progress made toward identification of effector repertoires from phloem-feeding insects and developments in effector biology that will advance functional characterization studies. Importantly, identification of effector activities from herbivorous insects promises to provide new avenues toward development of crop protection strategies. [Graphic: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Similar to plant pathogens, phloem-feeding insects such as aphids deliver effector proteins inside their hosts that act to promote host susceptibility and enable feeding and infestation. Despite exciting progress toward identifying and characterizing effector proteins from these insects, their functions remain largely unknown. The recent groundbreaking development in protein structure prediction algorithms, combined with the availability of proteomics and transcriptomic datasets for agriculturally important pests, provides new opportunities to explore the structural and functional diversity of effector repertoires. In this study, we sought to gain insight into the infection strategy used by the Myzus persicae (green peach aphid) by predicting and analyzing the structures of a set of 71 effector candidate proteins. We used two protein structure prediction methods, AlphaFold and OmegaFold, that produced mutually consistent results. We observed a wide continuous spectrum of structures among the effector candidates, from disordered proteins to globular enzymes. We made use of the structural information and state-of-the-art computational methods to predict M. persicae effector protein properties, including function and interaction with host plant proteins. Overall, our investigation provides novel insights into prediction of structure, function, and interaction of M. persicae effector proteins and will guide the necessary experimental characterization to address new hypotheses. [Graphic: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

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.

In a survey of the arthropod fauna of 33 Urban Green Spaces (UGS) in Bogotá, Colombia, between 2017 and 2019, 21 species (3,825 specimens) of Psylloidea were collected. These represent all seven recognised families of jumping plant-lice and include seven species identified only to genus. The specimens, all adults, were collected on 30 plant species used for arborization in the UGS. Two species are described as new (Mastigimas longicaudatus Rendón-Mera, Burckhardt & Vargas-Fonseca, sp. nov. and Leuronota albilinea Rendón-Mera, Burckhardt & Vargas-Fonseca, sp. nov.), one species is redescribed (Mastigimas colombianus Burckhardt, Queiroz & Drohojowska) and one species is recorded for the first time from Colombia (Calinda trinervis Olivares & Burckhardt). Among the seven species identified only to genus is an undescribed species of Melanastera, representing a genus not previously known from Colombia. Fourteen species found during the survey are probably native (66%) and seven (33%) adventive. Our findings highlight the significance of UGS for preservation of biological diversity and stress the importance of using native plants in urban landscape planning for the conservation of the native entomofauna. [ABSTRACT FROM AUTHOR]

Landscape fragmentation caused by agricultural expansion directly influences the spatial distribution of habitats and resources, favoring populations of pest insects such as the polyphagous whitefly Bemisia tabaci. Therefore, pest insects may constantly be dispersing between large- and small-scale crops that vary in quality and size at the landscape level. We aimed to understand how habitat use, dispersal movement and population dynamics of B. tabaci occur between large-scale and small-scale crops. We conducted a field experiment in large-scale soybean farms and small-scale farms cropping tomato plants in Brazil for two years. We collected soybean and tomato plant samples and adult whiteflies on these plants at different times of the phenological cycle of the crops. We determined the carbon and nitrogen stable isotope ratios of the plants and the whiteflies collected on these plants. We also estimated the population densities of whiteflies over time on these crops. We found that whitefly populations behave as metapopulations connected by dispersal. The isotopic ratios of B. tabaci revealed that large-scale soybean crops are source habitats of whitefly populations that, after harvest, disperse and redistribute among small-scale tomato farms causing a cascading effect on population growth on the latter. Therefore, understanding the spatial dynamics and management of pests such as whiteflies requires regional strategies, including large-scale and adjacent small-scale crops. C and N stable isotopes used here were able to track pest populations at the landscape level and, therefore, could be helpful to subsidize area-wide pest management strategies of whiteflies. [ABSTRACT FROM AUTHOR]

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Brassica vegetable and oilseed crops are attacked by several different flea beetle species (Chrysomelidae: Alticini). Over the past decades, most research has focused on two Phyllotreta species, Phyllotreta striolata and Phyllotreta cruciferae, which are major pests of oilseed rape in North America. More recently, and especially after the ban of neonicotinoids in the European Union, the cabbage stem flea beetle, Psylliodes chrysocephala, has become greatly important and is now considered to be the major pest of winter oilseed rape in Europe. The major challenges to flea beetle control are the prediction of population dynamics in the field, differential susceptibility to insecticides, and the lack of resistant plant cultivars and other economically viable alternative management strategies. At the same time, many fundamental aspects of flea beetle biology and ecology, which may be relevant for the development of sustainable control strategies, are not well understood. This review focuses on the interactions between flea beetles and plants and summarizes the literature on current management strategies with an emphasis on the potential for biological control in flea beetle management. [ABSTRACT FROM AUTHOR]

Invasive alien plants (weeds) are a growing, worldwide problem. Importation ('classical') biological control, using exotic insects, may be a key component in controlling invasive plants. Two‐thirds of plant species targeted worldwide by biocontrol programs experience some level of control, but the success rates are geographically variable and still hard to predict. Better understanding of the interactions of the species involved, and the effects of changing climate, may help to further improve both the efficacy and the predictability of this method. This requires pre‐release studies, as well as post‐release studies that quantify the impact at the population level to validate methodologies and assumptions of pre‐release studies. The 12 original papers of this special issue include pre‐ and post‐release studies on 13 insect species from five orders. The studies cover a wide range of methodologies and altogether they highlight that both target and non‐target impact are highly context dependent. This dedicated issue includes directions for methodological improvements to better assess ecological host ranges of agents and to avoid rejection of safe agents. [ABSTRACT FROM AUTHOR]

Sahlbergella singularis is a major insect pest of cocoa in Cameroon. Conventional insecticides remain the most widely used option for mirid control, which unfortunately have adverse effects on the environment and human health. Improved methods of controlling this species, both environmentally friendly and inexpensive to farmers, are requirements. Varietal control based on the selection of resistant and/or tolerant genotypes can be an interesting approach. Nonetheless, the role of secondary metabolites (SMs) in cocoa defense against mirids is poorly documented; yet, these compounds are reported to be key elements in plant defense against herbivores. For this purpose, SMs of twelve cocoa genotypes were identified and quantified, as well as their impact on food preference by mirids. Food preference was assessed through microtests measuring cocoa attractiveness and antixenosis toward mirids. The results showed that cocoa genotypes were differently accepted as food by mirids, with a significant preference for hybrid IMC60 x SNK605 and a non-preference for T60/887. The ten other cocoa genotypes showed intermediate results. Five SMs classes: alkaloids, flavonoids, polyphenols, saponins, and tannins were identified. Their rates varied between cocoa genotypes: polyphenols > alkaloids > flavonoids > tannins, and saponins. Cocoa genotypes with high total phenolic contents were significantly preferred by S. singularis (rα = 0.86, R2 = 74.0%, P < 0.001), while those with low saponins contents were lowly accepted (rα = − 0.83, R2 = 68.9%, P < 0.015), independently of the levels of other SMs. Given SMs high potential to affect mirid feeding behavior, analyzing cocoa SMs composition may help in early selection of resistant cocoa varieties against S. singularis.

Weevils are an unusually species-rich group of phytophagous insects for which there is increasing evidence of frequent involvement in brood-site pollination. This study examines phylogenetic patterns in the emergence of brood-site pollination mutualism among one of the most speciose beetle groups, the flower weevils (subfamily Curculioninae). We analysed a novel phylogenomic dataset consisting of 214 nuclear loci for 202 weevil species, with a sampling that mainly includes flower weevils as well as representatives of all major lineages of true weevils (Curculionidae). Our phylogenomic analyses establish a uniquely comprehensive phylogenetic framework for Curculioninae and provide new insights into the relationships among lineages of true weevils. Based on this phylogeny, statistical reconstruction of ancestral character states revealed at least 10 independent origins of brood-site pollination in higher weevils through transitions from ancestral associations with reproductive structures in the larval stage. Broadly, our results illuminate the unexpected frequency with which true weevils—typically specialized phytophages and hence antagonists of plants—have evolved mutualistic interactions of ecological significance that are key to both weevil and plant evolutionary fitness and thus a component of their deeply intertwined macroevolutionary success. [ABSTRACT FROM AUTHOR]

Insect-associated bacteria can mediate the intersection of insect and plant immunity. In this study, we aimed to evaluate the effects of single isolates or communities of gut-associated bacteria of Helicoverpa zea larvae on herbivore-induced defenses in tomato. We first identified bacterial isolates from the regurgitant of field-collected H. zea larvae by using a culture-dependent method and 16S rRNA gene sequencing. We identified 11 isolates belonging to the families Enterobacteriaceae, Streptococcaceae, Yersiniaceae, Erwiniaceae, and unclassified Enterobacterales. Seven different bacterial isolates, namely Enterobacteriaceae-1, Lactococcus sp., Klebsiella sp. 1, Klebsiella sp. 3, Enterobacterales, Enterobacteriaceae-2, and Pantoea sp., were selected based on their phylogenetic relationships to test their impacts on insect-induced plant defenses. We found that the laboratory population of H. zea larvae inoculated with individual isolates did not induce plant anti-herbivore defenses, whereas larvae inoculated with a bacterial community (combination of the 7 bacterial isolates) triggered increased polyphenol oxidase (PPO) activity in tomato, leading to retarded larval development. Additionally, field-collected H. zea larvae with an unaltered bacterial community in their gut stimulated higher plant defenses than the larvae with a reduced gut microbial community. In summary, our findings highlight the importance of the gut microbial community in mediating interactions between herbivores and their host plants. [ABSTRACT FROM AUTHOR]

Insect artificial diets are not only an important tool for mass rearing, nutritional research, and maintaining laboratory colonies but also for studying insect‐plant interactions. For herbivorous insects able to sequester plant toxins, feeding and sequestration assays based on artificial diet allow for the investigation of physiological, ecological, and evolutionary questions which may be difficult to study using real plants representing complex chemical environments. We developed a simple artificial diet, consisting of sunflower meal pressed into pills, for the milkweed bugs Oncopeltus fasciatus (Dallas) and Spilostethus saxatilis (Scopoli) (Heteroptera: Lygaeidae), which are capable of sequestering cardenolides and colchicum alkaloids, respectively. We assessed insect performance, suitability of the diet for sequestration assays, and its shelf life. Compared to sunflower seeds which are widely used as a laboratory maintenance diet for milkweed bugs, no differences were found in terms of weight development, presence of deformities, speed of development, or mortality. Importantly, after feeding O. fasciatus and S. saxatilis sunflower pills enriched with crystalline ouabain (cardenolide) or colchicine (colchicum alkaloid), respectively, sequestration was observed in both species. Moreover, as a prerequisite to test ecological hypotheses, our method allows for adequate concentration control and homogenous distribution of toxins across the diet. Under relatively warm conditions (27 °C and 60% r.h.), the new diet was stable for up to 10 days when used for feeding assays with adult bugs. Therefore, studies focusing on the role of plant toxins in predator–prey interactions and plant defense, but also insecticide research could benefit from using this approach. [ABSTRACT FROM AUTHOR]

The pollinating role of insects preceded the evolution of flowers. Insects pollinated gymnosperms before the appearance of angiosperms. The oldest record of pollinating insects is from the Upper Jurassic (~163 Ma), demonstrating the antiquity of animal pollination. We present a protocol for the definition and classification of pollinators and presumed pollinators in the fossil record of insects. Detailed study of bioinclusions in amber and fossil compressions can provide invaluable data for understanding insect-plants interactions in deep time. Inferring insect pollination from compression fossils and amber inclusions is difficult because of a lack of consensus on defining an insect pollinator and the challenge of recognizing this ecological relationship in deep time. We propose a conceptual definition for such insects and an operational classification into pollinator or presumed pollinator. Using this approach, we identified 15 insect families that include fossil pollinators and show that pollination relationships have existed since at least the Upper Jurassic (~163 Ma). Insects prior to this can only be classified as presumed pollinators. This gives a more nuanced insight into the origin and evolution of an ecological relationship that is vital to the establishment, composition and conservation of modern terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Flowers can be a valuable food source for primarily leaf‐feeding insects. They may also be an alternative diet when preferred foods are unavailable. Here we explored the value of florivory for the invasive viburnum leaf beetle (VLB). In the field, VLB larvae have been observed to feed on V. tinus inflorescences in the absence of young leaves, their preferred food. Under controlled conditions, we measured VLB larval performance when larvae were fed young V. tinus leaves, old (from the previous year's growth) V. tinus leaves, and V. tinus inflorescences. VLB larvae could complete their development by feeding solely on V. tinus inflorescences, with a negative impact on performance: larval survivorship to adult stage and adult mass decreased and developmental time increased when larvae fed on inflorescences. Survivorship was null when larvae were fed old leaves. Florivory appears to be a suboptimal diet for VLB, which may be used as a last resort when better food sources are absent. These results illustrate the importance of plasticity for the nutritional ecology of herbivorous insects. Dietary flexibility may have facilitated VLB's adoption of novel host plants in its invasive range. [ABSTRACT FROM AUTHOR]

Floral plantings adjacent to crops fields can recruit populations of natural enemies by providing flower nectar and non‐crop prey to increase natural pest regulation. Observed variation in success rates might be due to changes in the unseen community of endosymbionts hosted by many herbivorous insects, of which some can confer resistance to natural enemies, for example, parasitoid wasps. Reduced insect control may occur if highly protective symbiont combinations increase in frequency via selection effects, and this is expected to be stronger in lower diversity systems.We used a large‐scale field trial to analyse the bacterial endosymbiont communities hosted by cereal aphids Sitobion avenae collected along transects into strip plots of barley plants managed by either conventional or integrated (including floral field margins and reduced inputs) methods. In addition, we conducted an outdoor pot experiment to analyse endosymbionts in S. avenae aphids collected on barley plants that were either grown alone or alongside one of three flowering plants, across three time points.In the field, aphids hosted up to four symbionts. The abundance of aphids and parasitoid wasps was reduced towards the middle of all fields while aphid symbiont species richness and diversity decreased into the field in conventional, but not integrated, field‐strips. The proportion of aphids hosting different symbiont combinations varied across cropping systems, with distances into the fields, and were correlated with parasitoid wasp abundances.In the pot experiment, aphids hosted up to six symbionts. Flower presence increased natural enemy abundance and diversity, and decreased aphid abundance. The proportion of aphids hosting different symbiont combinations varied across the flower treatment and time, and were correlated with varying abundances of the different specialist parasitoid wasp species recruited by different flowers.Synthesis and applications. Floral plantings and flower identity had community‐wide impacts on the combinations of bacterial endosymbionts hosted by herbivorous insects, which correlated with natural enemy diversity and abundance. We recommend that integrated management practices incorporate floral resources within field areas to support a more functionally diverse and resilient natural enemy community to mitigate selection for symbiont‐mediated pest resistance throughout the cropping area. [ABSTRACT FROM AUTHOR]

Genome re-arrangements such as chromosomal inversions are often involved in adaptation. As such, they experience natural selection, which can erode genetic variation. Thus, whether and how inversions can remain polymorphic for extended periods of time remains debated. Here we combine genomics, experiments, and evolutionary modeling to elucidate the processes maintaining an inversion polymorphism associated with the use of a challenging host plant (Redwood trees) in Timema stick insects. We show that the inversion is maintained by a combination of processes, finding roles for life-history trade-offs, heterozygote advantage, local adaptation to different hosts, and gene flow. We use models to show how such multi-layered regimes of balancing selection and gene flow provide resilience to help buffer populations against the loss of genetic variation, maintaining the potential for future evolution. We further show that the inversion polymorphism has persisted for millions of years and is not a result of recent introgression. We thus find that rather than being a nuisance, the complex interplay of evolutionary processes provides a mechanism for the long-term maintenance of genetic variation. [ABSTRACT FROM AUTHOR]

Butterfly-host plant relationships can inform our understanding of ecological and trophic interactions that contribute to ecosystem function, resiliency, and services. The ecology of danaid-milkweed (Apocynaceae) host plant interactions has been studied in several biomes but is neglected in deserts. Our objective was to determine effects of plant traits, seasonality, and landscape-level host plant availability on selection of Mojave milkweed (Asclepias nyctaginifolia A. Gray) by ovipositing monarch butterflies (Danaus plexippusplexippus) and queen butterflies (Danaus gilippus thersippus) in the Californian Mojave Desert. We surveyed all known Mojave milkweed locations in the Ivanpah Valley, California (n = 419) during early, mid-, and late spring in 2017. For each survey, we counted monarch and queen butterfly eggs on each Mojave milkweed plant. We also measured canopy cover, height, volume, and reproductive stage of each Mojave milkweed plant. We counted a total of 276 queen butterfly eggs and zero monarch butterfly eggs on Mojave milkweed host plants. We determined that count of queen butterfly eggs significantly increased with increasing Mojave milkweed canopy cover. Additionally, count of queen butterfly eggs was: (1) greater on adult Mojave milkweed plants than on juvenile and seedling plants and greater on juvenile Mojave milkweed plants than on seedling plants; and (2) greater during early spring than mid-spring-we recorded no eggs during late spring. Based on aggregation indices, queen butterfly eggs occurred on Mojave milkweed plants in a nonrandom, clustered pattern throughout the Ivanpah Valley. We provide the first evidence of trophic interactions between queen butterflies and Mojave milkweed at multiple spatial scales in the Mojave Desert, suggesting that conservation and management practices for both species should be implemented concurrently. Given its role as an herbivore, pollinator and prey, the queen butterfly may serve as a model organism for understanding effects of anthropogenic disturbance (e.g., solar energy development) on "bottom-up" and trophic interactions among soils, plants and animals in desert ecosystems.

Resource specialization and ecological speciation arising through host‐associated genetic differentiation (HAD) are frequently invoked as an explanation for the high diversity of plant‐feeding insects and other organisms with a parasitic lifestyle. While genetic studies have demonstrated numerous examples of HAD in insect herbivores, the rarity of comparative studies means that we still lack an understanding of how deterministic HAD is, and whether patterns of host shifts can be predicted over evolutionary timescales. We applied genome‐wide single nucleotide polymorphism and mitochondrial DNA sequence data obtained through genome resequencing to define species limits and to compare host‐plant use in population samples of leaf‐ and bud‐galling sawflies (Hymenoptera: Tenthredinidae: Nematinae) collected from seven shared willow (Salicaceae: Salix) host species. To infer the repeatability of long‐term cophylogenetic patterns, we also contrasted the phylogenies of the two galler groups with each other as well as with the phylogeny of their Salix hosts estimated based on RADseq data. We found clear evidence for host specialization and HAD in both of the focal galler groups, but also that leaf gallers are more specialized to single host species compared with most bud gallers. In contrast to bud gallers, leaf gallers also exhibited statistically significant cophylogenetic signal with their Salix hosts. The observed discordant patterns of resource specialization and host shifts in two related galler groups that have radiated in parallel across a shared resource base indicate a lack of evolutionary repeatability in the focal system, and suggest that short‐ and long‐term host use and ecological diversification in plant‐feeding insects are dominated by stochasticity and/or lineage‐specific effects. [ABSTRACT FROM AUTHOR]

Plants generate energy flows through natural food webs, driven by competition for resources among organisms, which are part of a complex network of multitrophic interactions. Here, we demonstrate that the interaction between tomato plants and a phytophagous insect is driven by a hidden interplay between their respective microbiotas. Tomato plants colonized by the soil fungus Trichoderma afroharzianum, a beneficial microorganism widely used in agriculture as a biocontrol agent, negatively affects the development and survival of the lepidopteran pest Spodoptera littoralis by altering the larval gut microbiota and its nutritional support to the host. Indeed, experiments aimed to restore the functional microbial community in the gut allow a complete rescue. Our results shed light on a novel role played by a soil microorganism in the modulation of plant–insect interaction, setting the stage for a more comprehensive analysis of the impact that biocontrol agents may have on ecological sustainability of agricultural systems. [ABSTRACT FROM AUTHOR]

Microbes are known to influence insect-plant interactions; however, it is unclear if host-plant diet influences the regulation of nutritional insect symbioses. The pea aphid, Acyrthosiphon pisum, requires its nutritional endosymbiont, Buchnera, for the production of essential amino acids. We hypothesize that key aphid genes that regulate the nutritional symbioses respond to host-plant diet when aphids feed on a specialized (alfalfa) compared to a universal host-plant diet (fava), which vary in amino acid profiles. Using RNA-Seq and whole genome bisulfite sequencing, we measured gene expression and DNA methylation profiles for such genes when aphids fed on either their specialized or universal host-plant diets. Our results reveal that when aphids feed on their specialized host-plant they significantly up-regulate and/or hypo-methylate key aphid genes in bacteriocytes related to the amino acid metabolism, including glutamine synthetase in the GOGAT cycle that recycles ammonia into glutamine and the glutamine transporter ApGLNT1 Moreover, regardless of what host-plant aphids feed on we observed significant up-regulation and differential methylation of key genes involved in the amino acid metabolism and the glycine/serine metabolism, a metabolic program observed in proliferating cancer cells potentially to combat oxidative stress. Based on our results, we suggest that this regulatory response of key symbiosis genes in bacteriocytes allows aphids to feed on a suboptimal host-plant that they specialize on.

To avoid the activation of plant defenses and ensure sustained feeding, aphids are assumed to use their mouthparts to deliver effectors into plant cells. A recent study has shown that effectors detected near feeding sites are differentially distributed in plant tissues. However, the precise process of effector delivery into specific plant compartments is unknown. The acrostyle, a cuticular organ located at the tip of maxillary stylets that transiently binds plant viruses via its stylin proteins, may participate in this specific delivery process. Here, we demonstrate that Mp10, a saliva effector released into the plant cytoplasm during aphid probing, binds to the acrostyles of Acyrthosiphon pisum and Myzus persicae. The effector probably interacts with Stylin-03 as a lowered Mp10-binding to the acrostyle was observed upon RNAi-mediated reduction in Stylin-03 production. In addition, Stylin-03 and Stylin-01 RNAi aphids exhibited changes in their feeding behavior as evidenced by electrical penetration graph experiments showing longer aphid probing behaviors associated with watery saliva release into the cytoplasm of plant cells. Taken together, these data demonstrate that the acrostyle also has effector binding capacity and supports its role in the delivery of aphid effectors into plant cells. [ABSTRACT FROM AUTHOR]

Forage Sorghum Yield In Tifton, in 2021, yield was unaffected by planting date ( I F i = 2.34; df = 1,29; I p i = 0.1410) and insecticide application ( I F i = 0.5241; df = 3,29 I p i = 0.6891) and there was no significant interaction between planting date and insecticide treatment ( I F i = 0.25; df = 1,29; I p i = 0.8591) (Figure 5). Thus, this suggests that early planting of forage sorghum and in-furrow insecticide application is the most consistent way to suppress aphid infestations and improve silage production in southern USA. Sudden I M. sorghi i populations declines, and even collapse, have also been observed in other sorghum studies throughout the southeastern US states [[4], [11]] The reduced aphid infestations in the early planted sorghum in 2020 in Florence significantly increased forage sorghum yield; late planted sorghum suffered over 50% yield loss. Keywords: insecticide efficacy; aphid infestation; foliar application; in-furrow application; insect-plant interactions; early planting; late planting EN insecticide efficacy aphid infestation foliar application in-furrow application insect-plant interactions early planting late planting 1038 12 11/17/22 20221101 NES 221101 1. [Extracted from the article]

Potato, a cool‐weather crop, emits volatile organic compounds (VOCs) which attract the specialist herbivore, Phthorimaea operculella, but also this herbivore's parasitic wasp, Trichogramma chilonis, an important biocontrol agent. What happens to this trophic system when heat stress challenges this agro‐ecosystem? We studied how high temperature (HT) pre‐treatments influence potato's VOC emissions and their subsequent effects on the preferences of insects, as evaluated in oviposition assays and Y‐tube olfactometers. HT pre‐stressed plants were less attractive to P. operculella adult moths, which were repelled by HT VOCs, but increased the recruitment of the parasitoid, T. chilonis, which were attracted. VOC emissions, including the most abundant constituent, ß‐caryophyllene, were enhanced by HT treatments; some constituents elicited stronger behavioural responses than others. Transcripts of many genes in the biosynthetic pathways of these VOCs were significantly enhanced by HT treatment, suggesting increases in de novo biosynthesis. HT increased the plant's stomatal apertures, and exogenous applications of the hormone, ABA, known to suppress stomatal apertures, reduced leaf volatile emissions and affected the HT‐altered plant attractions to both insects. From these results, we infer that HT stress affects this plant‐insect interaction through its influence on VOC emissions, potentially decreasing herbivore ovipositions while increasing ovipositions of the parasitoid. [ABSTRACT FROM AUTHOR]

The larvae of insect herbivores feed on plants that may vary nutritionally (qualitatively and/or quantitatively) over the course of insect development. Plant quality may change in response to interactions with the biotic environment that in turn may affect development and biomass of the insects feeding on these plants. However, the larvae of many gregariously feeding herbivores feed on comparatively small plants with limited biomass and may also experience variation in the quantity of plant food available. Pieris brassicae L. (Lepidoptera: Pieridae) is a gregarious butterfly species laying clutches of 10–150 eggs that are often laid on small brassicaceous food plants, including the plant used in this study, Brassica nigra L. (Brassicaceae). A single B. nigra plant provides insufficient resources for the development of an entire brood of P. brassicae. In this study, we investigated the effect of both plant quality and quantity on the performance of P. brassicae when feeding on B. nigra plants. When we compared the effects of changes in plant quality induced by (1) aphid infestation, (2) exposure to pathogenic and non‐pathogenic bacteria, and (3) inbreeding depression, which are all biotic stresses known to change plant quality, pupal mass and larval development time of P. brassicae were fairly similar. We then examined the effects of quantitative food constraints during immature development on pupal mass, which correlated strongly with adult size, longevity, and fecundity. Female pupal mass, longevity and fecundity were negatively correlated with the duration of starvation during larval development. No significant effect of male starvation was found on female reproduction and longevity. Thus, P. brassicae larvae were more affected by quantitative than by qualitative constraints in terms of pupal mass, which strongly correlated with female reproduction. [ABSTRACT FROM AUTHOR]

In South America, maize (Zea mays L., Poaceae) crops are commonly infested with larvae of Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), known as voracious leaf feeders, as well as by larvae of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae), a pest that destroys maize root systems. Despite the relevance of these insects to maize fields, there is no information available about the effects of these herbivores on one another. Therefore, this study aimed to evaluate in different maize varieties: (1) the influence of previous leaf consumption by S. frugiperda on D. speciosa larval weight and survival, (2) effects of previous root attack by D. speciosa on S. frugiperda larval weight and survival, and (3) the relationship between peroxidase and superoxide dismutase (resistance‐related enzymes) and maize resistance to the pests. One fifth instar S. frugiperda was released per potted maize plant at vegetative stage 4 (V4), and 24 h later plants were infested with 25 D. speciosa larvae. One set of plants was infested with D. speciosa only, and 16 days later whorl leaf sections were brought to the laboratory and offered to S. frugiperda neonate larvae. Performance of both insect pests was determined based on larval weight and survival. Uninfested plants of variety Maisena were susceptible to both herbivores. However, plants of this variety pre‐infested with S. frugiperda disfavored D. speciosa larval survival. Similarly, plants of variety Maisena pre‐infested with D. speciosa adversely affected S. frugiperda larval growth. Nevertheless, this induction of resistance was inhibited when the plant was also pre‐infested with S. frugiperda. In most cases, peroxidase and superoxide dismutase did not seem to play a role in mediating resistance to the pests. Overall, variety Maisena appears as a template for the development of maize genotypes expressing induced resistance. The potential of some varieties regarding constitutive resistance is also discussed. [ABSTRACT FROM AUTHOR]