Aphid Species Research Articles

Evolution of secondary metabolites, morphological structures and associated gene expression patterns in galls induced by four closely related aphid species on a host plant species.

Gall-forming insects induce various types of galls on their host plants by altering gene expression in host plant organs, and recent studies have been conducted for gene expression in galls. However, the evolutionary trajectories of gene expression patterns and the resulting phenotypes have not yet been studied using multiple related species. We investigated the speciation and the diversification process of galls induced by four closely related aphid species (Hormaphidini) on a host plant species (Hamamelis japonica) by examining the phylogenetic congruence between the geographical divergences of aphids and the host plant, and by comparing their gene expression patterns and resulting phenotypes. Phylogenetic analysis of aphids and the host plant showed that geographical isolation among host plant populations has interrupted gene flow in aphids and accelerated the speciation process. The concentration of phenolics and the complexity of the internal structure of galls were correlated with the expression levels of genes for the biosynthesis of phenolics and morphogenesis respectively. These results suggest that the expression levels of genes for the biosynthesis of phenolics and morphogenesis have evolutionarily increased in galls accelerated by the speciation process of aphids due to the distribution change of the host plant, leading to the related phenotypic evolution. Our study showed the evolutionary process of phenotypic traits in galls in the wild from both gene expression and actual phenotype levels.

Prevalence and Diversity of Aphid-Vectored Yellow Dwarf Viruses in Oregon Perennial Grass Seed Crops

Oregon produces 70% of the world's cool-season grass seed, many species of which are susceptible to yellow dwarf viruses (YDVs). This virus complex has numerous defined virus species vectored by multiple aphid species. The diversity of YDVs associated with Oregon grass seed production has not been determined and is needed to provide insight to develop a risk prediction framework and improve management guidelines to mitigate disease severity. Commercial grass seed fields ( n = 57) across the Willamette Valley and central and eastern Oregon were surveyed across 2021 and 2022 to determine the incidence and diversity of YDVs associated with crop species (perennial ryegrass, tall fescue, and Kentucky bluegrass) and the abundance and incidence of YDVs associated with aphid vectors. Virus incidence and diversity were determined using multiple previously published endpoint reverse-transcriptase multiplexes specific for YDV genera and species. Across commercial grass seed crop hosts and growing seasons, 82% of fields had at least one plant sample detection of a luteovirus-type YDV, and 65% had at least one detection of a polerovirus-type YDV. Both perennial ryegrass and tall fescue crops hosted diverse YDV populations, which was especially apparent during the spring sampling season, when similarly diverse YDV communities were found associated with alate aphids. Only polerovirus-type YDVs were detected in Kentucky bluegrass, reflecting a variable landscape compared to Oregon's western Willamette Valley. This study provides a current understanding of the spatial composition and diversity of the aphid–YDV virus–vector system in grasses grown for seed in Oregon. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Feeding specialization shapes the bottom‐up effect of arbuscular mycorrhizal fungi across a plant–aphid–parasitoid system

Societal Impact StatementArbuscular mycorrhizal fungi (AMF) impact the relationships between plants, aphids (insects that feed on plant phloem), and their natural enemies (insects that prey on or parasitize aphids). The presence of AMF influences the growth and population of different aphid species and affects the development of aphid‐killing wasps and their attraction to plants. This research has been conducted also considering the insects' feeding strategy and their feeding specialization. This study provides novel perspectives on how these fungi shape interactions in the natural world, offering potential insights for the development of sustainable pest management strategies in agriculture.Summary Arbuscular mycorrhizal fungi (AMF) are major root symbionts regulating plant physiology. Their presence affects the performance of aboveground insect herbivores in relation to their feeding strategy and their feeding specialization. For example, the effect of the arbuscular mycorrhizal (AM) symbiosis on chewing insects, positive for specialists and negative for generalists, has been previously demonstrated. Conversely, the impact of AMF on phloem‐suckers with relatively different levels of specialization remains unexplored. We tested the influence of the AM Funneliformis mosseae on the fitness of the specialist aphid Acyrthosiphon pisum and the generalist aphid Myzus persicae on Vicia faba plants. Further, we investigated the effects of AMF on the higher trophic level, the aphid parasitoids Aphidius ervi (specialist) and Aphidius colemani (generalist), by evaluating plant attractiveness and parasitoid fitness. To support the results of behavioral and biological bioassays we characterized the photosynthetic parameters, the volatilome and the transcriptome of tested plants. Mycorrhizal plants proved unsuitable for the generalist M. persicae but enhanced the fitness of the specialist A. pisum. The AM symbiosis had no effects on the behavioral response of A. colemani and enhanced the attraction and fitness of A. ervi. Volatilome and transcriptome profiling corroborated the results of bioassay highlighting a bottom‐up effect of the AMF across a plant–aphid–parasitoid system.

The first record of Illinoia liriodendri (Monell, 1879) (Hemiptera, Aphididae) from Ukraine

Illinoia liriodendri is reported for the first time in Ukraine as a new invasive species of aphids. It was found feeding on Liriodendron tulipifera at the ‘Olexandria’ State Dendrological Park of the NAS of Ukraine in June 2024.

A molecular approach to unravel trophic interactions between parasitoids and hyperparasitoids associated with pecan aphids.

Advances in molecular ecology can overcome many challenges in understanding host-parasitoid interactions. Genetic characterization of the key-players in systems helps to confirm species and identify trophic linkages essential for ecological service delivery by biological control agents; however, relatively few agroecosystems have been explored using this approach. Pecan production consists of a large tree perennial system containing an assortment of seasonal pests and natural enemies. As a first step to characterizing host-parasitoid associations in pecan food webs, we focus on aphid species and their parasitoids. Based on DNA barcoding of field-collected and reared specimens, we confirmed the presence of 3 species of aphid, one family of primary parasitoids, and 5 species of hyperparasitoids. By applying metabarcoding to field-collected aphid mummies, we were able to identify multiple species within each aphid mummy to unravel a complex food web of 3 aphids, 2 primary parasitoids, and upward of 8 hyperparasitoid species. The results of this study demonstrate that multiple hyperparasitoid species attack a single primary parasitoid of pecan aphids, which may have negative consequences for successful aphid biological control. Although further research is needed on a broader spatial scale, our results suggest multiple species exist in this system and may suggest a complex set of interactions between parasitoids, hyperparasitoids, and the 3 aphid species. This was the first time that many of these species have been characterized and demonstrates the application of novel approaches to analyze the aphid-parasitoid food webs in pecans and other tree crop systems.

Efficacy of 2 botanical aphicides, chicoric and 3,5-dicaffeoylquinic acids, on aphids susceptible and resistant to synthetic insecticides.

Dicaffeoyltartaric acid (diCT) and 3,5-dicaffeoylquinic acid (3,5-diCQ) are described for their aphicidal properties on several aphid species. Intending to valorize diCT and 3,5-diCQ as biocontrol products and because of the high adaptive capacities of aphids to xenobiotics, we sought to determine the existence of adaptation first in Myzus persicae (Sulzer) (Hemiptera: Aphididae) and then other aphids. Resistance of aphids to these biopesticides could be promoted by (i) the existence of resistance to synthetic insecticides that may confer cross-resistance and (ii) the presence of these compounds in wild plants likely which may have led to pre-existing adaptation in aphids. We assessed the resistance levels to diCT and 3,5-diCQ in 7 lab strains (including some resistant to synthetic aphicides) and 7 wild populations of M. persicae using biotests. The activities of detoxification enzymes contributing to insecticide resistance were also measured. Additionally, we followed the same method to characterize susceptibility to these caffeic derivatives in wild populations of Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), Brevicoryne brassicae(Linnaeus) (Hemiptera: Aphididae) and, Aphis craccivora(Koch) (Hemiptera: Aphididae). Our results show variability in susceptibility to diCT between populations of M. persicae, but resistance ratios (RR) were low (RR = 3.59). We found no cross-resistance between synthetic insecticides and diCT. Carboxylesterase and glutathione-S-transferase did not seem to be involved in its detoxification. A clone of A. craccivora collected from peanut, a species rich in diCT, was not susceptible to either diCT or 3,5-diCQ, suggesting a common molecular target for these 2 molecules and the existence of a high-effect resistance mechanism. These active botanical substances remain good candidates for M. persicae biocontrol in agriculture.

Population Growth Parameters of Scymnus nubilus Fed Single-Aphid Diets of Aphis fabae or Myzus persicae.

Life tables are an important tool to forecast the performance of biological control agents used in pest management programs, and they are often assessed in terms of population growth. In the present study, the suitability of the aphids Aphis fabae Scopoli and Myzus persicae (Sulzer) for the ladybird predator Scymnus nubilus Mulsant was assessed for the first time. For this, we evaluated and compared the life history traits of immature individuals and adults of the predator fed single-aphid diets and the consequences of the single-aphid diets for the demographic parameters. Scymnus nubilus that were fed A. fabae were significantly more fecund and presented a shorter immature development time than those fed M. persicae. The predators fed A. fabae had a significantly higher net reproductive rate, an intrinsic and finite rate of increase, while their doubling time was significantly lower than that of those fed M. persicae. The aphid species used in this study are new additions to the essential prey list of the ladybird, with the predator presenting a better biological performance than that found on the previously known essential prey species.

Novel transinfections of Rickettsiella do not affect insecticide tolerance in Myzus persicae, Rhopalosiphum padi, or Diuraphis noxia (Hemiptera: Aphididae).

Aphids (Hemiptera: Aphidoidea) are economically important crop pests worldwide. Because of growing issues with insecticide resistance and environmental contamination by insecticides, alternate methods are being explored to provide aphid control. Aphids contain endosymbiotic bacteria that affect host fitness and could be targeted as potential biocontrol agents, but such novel strategies should not impact the effectiveness of traditional chemical control. In this work, we used a novel endosymbiont transinfection to examine the impact of the endosymbiont Rickettsiella viridis on chemical tolerance in 3 important agricultural pest species of aphid: Myzus persicae (Sulzer) (Hemiptera: Aphididae), Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae), and Diuraphis noxia (Mordvilko ex Kurdjumov) (Hemiptera: Aphididae). We tested tolerance to the commonly used insecticides alpha-cypermethrin, bifenthrin, and pirimicarb using a leaf-dip bioassay. We found no observed effect of this novel endosymbiont transinfection on chemical tolerance, suggesting that the strain of Rickettsiella tested here could be used as a biocontrol agent without affecting sensitivity to insecticides. This may allow Rickettsiella transinfections to be used in combination with chemical applications for pest control. The impacts of other endosymbionts on insecticide tolerance should be considered, along with tests on multiple aphid clones with different inherent levels of chemical tolerance.

Robust species distribution predictions of predator and prey responses to climate change

AbstractAimSpecies distribution models (SDMs) can be correlative or mechanistic, which have very different assumptions, leading to potentially different estimates of the ecological niches and distributions of the species. The model predictions from correlative and mechanistic approaches are incomparable due to their distinct assumptions. Yet, seeking their agreements can identify robust predictions that are relatively independent of the assumptions used to generate them. However, the search for robust model predictions among SDM models remains understudied and rarely considers the effect of biotic interactions. It is essential to identify robust predictions from SDMs for policy making.LocationGlobal.Time Period1970–2000/1980–2000 and 2081–2100.Major Taxa StudiesAphids.MethodsIn this study, we selected five aphid species as examples, and applied an ensemble model of multiple correlative SDMs (eC‐SDM), a mechanistic SDM of the prey species alone (M‐SDM) and a mechanistic SDM of the predator–prey interactions (M‐BI‐SDM), to predict the habitat suitability of these aphids under climate change and seek robust predictions from both approaches, as well as evaluate the importance of biotic interactions in SDM studies.ResultsOur results show that the five aphid species have different habitat suitability patterns predicted by both correlative and mechanistic approaches. However, there is a notable consensus between the model predictions for parts of North America and eastern Asia, indicating that the predictions in these regions are robust. Additionally, our mechanistic models allow us to assess the importance of predation on SDM predictions, revealing that predation can quantitatively affect species' habitat suitability both directly and indirectly.Main ConclusionsOur study suggests that mechanistic SDM could serve as a valuable addition to assess the robustness of the correlative SDM predictions, by providing additional biological realism. It highlights the importance of using diverse modelling approaches to achieve robust model predictions.

Genome-Wide Comparative Analysis of the Cytochrome P450 Monooxygenase Family in 19 Aphid Species and Their Expression Analysis in 4 Cereal Crop Aphids.

Cytochrome P450 monooxygenases (CYP450s) play a variety of physiological roles, including pesticide resistance, plant allelochemical detoxification, and hormone metabolism catalysis. However, limited information is available on the classification and expression profiles of the CYP450 gene family in aphid species. This is the first study to identify the cytochrome P450 gene family in 19 aphid species at the whole genome level. A total of 1100 CYP450 genes were identified in 19 aphid species. Three hundred CYP450 genes belonged to six cereal crop aphid species, which were further classified into four subfamilies according to the phylogenetic relationship. The conserved motifs, exon-intron structures, and genomic organization of the same subfamilies were similar. Predictions of subcellular localization revealed that the endoplasmic reticulum harbored the majority of CYP450 proteins. In Sitobion avenae and Rhopalosiphum maidis, the increase in the CYP450 gene was primarily caused by segmental duplication events. However, only tandem duplication occurred in the CYP450 gene family of Diuraphis noxia, Rhopalosiphum padi, Schizaphis graminum, and Sitobion miscanthi. Synteny analysis found three continuous colinear CYP450 gene pairs among six cereal crop aphid species. Furthermore, we obtained the expression profiles of four cereal crop aphids, including R. padi, D. noxia, S. graminum, and S. avenae. Differential expression analysis provided growth stage specificity genes, tissue specificity genes, organ specificity genes and some detoxification metabolic genes among these four cereal crop aphids. Meanwhile, their expression patterns were showed. The related functions and pathways of CYP450s were revealed by GO and KEGG enrichment analysis. Above all, we picked the differentially expressed CYP450 genes from all of the differentially expressed genes (DEGs). These differentially expressed CYP450 genes provided some new potential candidates for aphid control and management. This work establishes the foundation for further investigations into the regulatory functions of the CYP450 gene family in aphid species and beyond.

The sublethal concentration of acetamiprid suppresses the population growth of 2 species of wheat aphids, Sitobion miscanthi and Schizaphis graminum (Hemiptera: Aphididae).

Sitobion miscanthi and Schizaphis graminum (Rondani) are the 2 main aphid species that occur simultaneously, causing significant loss to wheat production. Acetamiprid has been used to control a variety of pests, including aphids. In this study, the sublethal effect of acetamiprid on S. miscanthi and S. graminum was evaluated using life-table analyses. The results showed that acetamiprid has a high toxicity to S. miscanthi and S. graminum with a LC50 of 1.90 and 3.58 mg/L at 24 h, respectively. The adult longevity and fecundity of S. miscanthi and S. graminum F0 generation were significantly reduced after being exposed to a sublethal concentration of acetamiprid. Additionally, the sublethal concentration of acetamiprid had negative transgenerational effects on S. miscanthi and S. graminum, which showed a significant decrease in fecundity and population life-table parameters involving age-stage-specific survival rate (sxj), age-specific survival rate (lx), and intrinsic rate of increase (r). Furthermore, the population projections showed that the total population size of S. miscanthi and S. graminum was significantly lower in the aphid group exposed to sublethal concentration of acetamiprid compared to the control group. These results suggest that sublethal concentration of acetamiprid suppresses the population growth of S. miscanthi and S. graminum. This finding is beneficial to the control of wheat aphids, and is important to fully understand the role of acetamiprid in integrated pest management.

Circadian pattern in attendance of aphid colonies by ants

Ant-attendance of aphids is one of the subjects of interest in ecological studies as a reciprocal service providing benefits to both groups involved. The behavioural patterns in this relation depend on many factors, e.g. biology of the species involved, aphid host plants, activity of natural enemies and abiotic factors. In this respect, the circadian pattern of ant-attendance was almost unknown. The paper presents the results of the pattern of such circadian activity of ants Lasius niger and L. emarginatus attending six aphid species (Panaphis juglandis, Aphis grossulariae, A. urticata, A. umbrella, Myzus persicae and Aphis fabae) feeding on various types of plants and having various dependence of trophobiosis. The highest number of ant workers in aphid colonies was observed at night and dawn, while the lowest was just after solar noon. The circadian pattern of ant activity strongly depends on the weather, especially temperature and relative humidity, with the highest abundance of ants during humid and cool weather. The possible interconnection between the temperature-dependent activity of ants and the water-dependent physiological condition of certain plants is discussed and indicated as an explanation. The issue of possible work division among ant workers attending aphids as an explanation of the observed pattern of activity remains open.

Salivary gland transcriptomics of the cotton aphid Aphis gossypii and comparative analysis with other sap‐sucking insects

AbstractAphids are sap‐sucking insects responsible for crop losses and a severe threat to crop production. Proteins in the aphid saliva are integral in establishing an interaction between aphids and plants and are responsible for host plant adaptation. The cotton aphid, Aphis gossypii (Hemiptera: Aphididae) is a major pest of Gossypium hirsutum. Despite extensive studies of the salivary proteins of various aphid species, the components of A. gossypii salivary glands are unknown. In this study, we identified 123,008 transcripts from the salivary gland of A. gossypii. Among those, 2933 proteins have signal peptides with no transmembrane domain known to be secreted from the cell upon feeding. The transcriptome includes proteins with more comprehensive functions such as digestion, detoxification, regulating host defenses, regulation of salivary glands, and a large set of uncharacterized proteins. Comparative analysis of salivary proteins of different aphids and other insects with A. gossypii revealed that 183 and 88 orthologous clusters were common in the Aphididae and non‐Aphididae groups, respectively. The structure prediction for highly expressed salivary proteins indicated that most possess an intrinsically disordered region. These results provide valuable reference data for exploring novel functions of salivary proteins in A. gossypii with their host interactions. The identified proteins may help develop a sustainable way to manage aphid pests.

Further spread of the invasive apricot aphid Myzus mumecola (Hemiptera: Aphididae) in Central Europe and first insights into its phylogeny

AbstractA new aphid species infesting apricots (Prunus armeniaca L.) was identified for the first time in 2016 in Europe. The invasive aphid was assigned to the species Myzus mumecola (Matsumura, 1917). The species is native to India and East Asia, and it was found to be highly invasive and is currently spreading throughout Europe. Records were confirmed for Italy, Hungary, Serbia, and Germany. For a phylogenetic analysis, wingless (apterae) adults were sampled in spring 2022 in Italy, as well as in Austria and Germany in spring 2023. Our study reports the first record of M. mumecola for Austria. In all three countries, the new pest caused heavy infestations overall in organically managed apricot orchards. Aphids were identified morphologically based on external characteristics, and damages were compared to those reported in the literature. COI and 12S barcoding analyses for aphid samples from Italy, Germany, and Austria were performed to attain a molecular characterization of sampled specimens and to confirm the morphological identification. Only a few COI sequences of M. mumecola were present in NCBI GenBank or BOLD Systems, and no sequences were available for 12S. Therefore, the results provide a deeper insight into the phylogeny of this spreading pest insect. The results of the COI barcoding showed no differences between the sampled populations and other M. mumecola populations from Europe and Japan, while reports from China showed significant differences. All 12S sequences showed no variability between populations from Austria, Germany, and Italy. A phylogenetic analysis of COI and 12S sequences with sequences from other aphid species from NCBI GenBank or sampled in Italy revealed a close relationship of this species with the damson‐hope aphid, Phorodon humuli.

Landscapes with higher crop diversity have lower aphid species richness but higher plant virus prevalence

Abstract Diversifying agricultural systems by growing more than one crop species in an area can decrease pest and disease pressure and increase crop yields. However, there is a lack of information on how crop diversity at larger spatial scales influences pest and disease pressure. Here, we investigated how landscape‐scale crop diversity affects aphid vector communities and prevalence of non‐persistently transmitted potato virus Y (PVY). To test the influence of landscape‐scale crop diversity on PVY prevalence and aphid communities, we conducted a field study during the 2020 and 2021 field seasons in the San Luis Valley, Colorado, where we quantified aphid communities and PVY incidence at multiple sites. We then determined the association between aphid species richness and abundance and PVY incidence with landscape variables (crop diversity metrics and percentage cover of crop species) within 1, 2 and 3 km buffers from study sites. Higher crop diversity (measured as Shannon Diversity Index) led to decreased aphid species richness at a 3 km buffer in the 2021 field season. We only detected a positive association between percentage of alfalfa crop cover and aphid species richness in 2020 and aphid abundance in 2021 within a 1 km buffer. Higher crop diversity led to increased PVY incidence at a 2 km buffer in 2021 and 3 km buffer in 2020 and 2021. At a 3 km buffer in 2021, we found a positive influence of crop species richness on PVY incidence and a negative influence of crop species evenness on PVY incidence. Also in 2021, we found a positive influence of percentage of potato (virus host) on PVY incidence and a negative influence of percentage of barley (virus non‐host) on PVY incidence. Synthesis and applications. In summary, we found that landscape‐scale crop diversity impacts plant virus prevalence at spatial scales of >1 km. This suggests that potato growers could reduce PVY prevalence by geographically isolating potato fields from other potato or other PVY hosts. Crop diversity had a negative influence on aphid vector communities, so growers could reduce risk of virus spread by aphid vectors by using certified potato seed in a diversified landscape.

Exploring the potential of root-associated bacteria to control an outbreak weed

Abstract Aims The spread of invasive weeds threatens biodiversity and stability of ecosystems. Jacobaea vulgaris is an invasive weed in some countries and an outbreak species in its native European range. Although biological control using specialist herbivores is available, controlling with soil microorganisms remains far less explored. Methods Twenty bacteria strains isolated from roots of J. vulgaris were used to examine bacterial effects on seed germination, root morphology and early plant growth. Moreover, we tested direct effects of the bacteria on a specialist herbivore of J. vulgaris, the leaf chewing caterpillar (Tyria jacobaeae), commonly used in biocontrol. We also tested indirect effects of bacteria, via the plant, on the performance of T. jacobaeae and the aphid species Aphis jacobaeae. Lastly, we examined the host specificity of two tested bacteria on three other forbs. Results Two Gammaproteobacteria, Pseudomonas brassicacearum and Serratia plymuthica, significantly reduced root growth of seedlings in-vitro, while seed germination was unaffected. However, these negative effects were observed across other forb species as well. Bacillus spp. injection led to the highest T. jacobaeae caterpillar mortality, while ingestion had no effect. Inoculation of the plants with bacteria did not affect aphid performance, but significantly affected T. jacobaeae preference. Specifically, P. syringae and one Bacillus sp. strain significantly increased T. jacobaeae preference. Conclusions Our results show that two root-associated bacteria inhibit J. vulgaris growth, but their lack of host specificity restricts their potential for biocontrol. Our study also highlights that belowground microorganisms can hamper or enhance the performance of aboveground insects.

Ecological divergence despite common mating sites: Genotypes and symbiotypes shed light on cryptic diversity in the black bean aphid species complex.

Different host plants represent ecologically dissimilar environments for phytophagous insects. The resulting divergent selection can promote the evolution of specialized host races, provided that gene flow is reduced between populations feeding on different plants. In black bean aphids belonging to the Aphis fabae complex, several morphologically cryptic taxa have been described based on their distinct host plant preferences. However, host choice and mate choice are largely decoupled in these insects: they are host-alternating and migrate between specific summer host plants and shared winter hosts, with mating occurring on the shared hosts. This provides a yearly opportunity for gene flow among aphids using different summer hosts, and raises the question if and to what extent the ecologically defined taxa are reproductively isolated. Here, we analyzed a geographically and temporally structured dataset of microsatellite genotypes from A. fabae that were mostly collected from their main winter host Euonymus europaeus, and additionally from another winter host and fourteen summer hosts. The data reveals multiple, strongly differentiated genetic clusters, which differ in their association with different summer and winter hosts. The clusters also differ in the frequency of infection with two heritable, facultative endosymbionts, separately hinting at reproductive isolation and divergent ecological selection. Furthermore, we found evidence for occasional hybridization among genetic clusters, with putative hybrids collected more frequently in spring than in autumn. This suggests that similar to host races in other phytophagous insects, both prezygotic and postzygotic barriers including selection against hybrids maintain genetic differentiation among A. fabae taxa, despite a common mating habitat.

Does This Look Infected? Hidden Host Plant Infection by the Pathogen Botrytis cinerea Alters Interactions between Plants, Aphids and Their Natural Enemies in the Field.

Few studies have considered whether hidden (asymptomatic) plant pathogen infection alters ecological interactions at the higher trophic levels, even though such infection still affects plant physiology. We explored this question in two field experiments, where two varieties of lettuce (Little Gem, Tom Thumb) infected with Botrytis cinerea were either (1) naturally colonised by aphids or (2) placed in the field with an established aphid colony. We then recorded plant traits and the numbers and species of aphids, their predators, parasitoids and hyperparasitoids. Infection significantly affected plant quality. In the first experiment, symptomatically infected plants had the fewest aphids and natural enemies of aphids. The diversity and abundance of aphids did not differ between asymptomatically infected and uninfected Little Gem plants, but infection affected the aphid assemblage for Tom Thumb plants. Aphids on asymptomatically infected plants were less attractive to predators and parasitoids than those on uninfected plants, while hyperparasitoids were not affected. In the second experiment, when we excluded natural enemies, aphid numbers were lower on asymptomatically and symptomatically infected plants, but when aphid natural enemies were present, this difference was removed, most likely because aphids on uninfected plants attracted more insect natural enemies. This suggests that hidden pathogen infection may have important consequences for multitrophic interactions.

A Study of the Population Density of Aphids and Coccinella septempunctata on Different Wheat Cultivars

Background: Wheat is considered one of the primary and strategic grain crops in the world in terms of production and importance. The increment in both quantity and quality of wheat production renders it susceptible to various pests and diseases, including both insects and non-insect pests. The study aims to study the extent of infection of the IPA 99, IPA 22 and Abu Ghraib wheat varieties with aphids. Methods: A general survey of aphids on Abu Ghraib, IPA 99 and IPA 22 wheat varieties was carried out in the fields of the College of Agriculture/ University of Baghdad in Abu Ghraib during the growing season 2021-2022. Result: The results of the field survey indicated the presence of three species of aphids on the wheat crops belonging to the order Hemiptera and the family Aphididae: the wheat aphid [Schizaphis graminum (Rondani)], the oat aphid [Rhopalosiphum padi (L.)] and the corn aphid (Rhopalosiphum maidis). Wheat and oat aphids were the most commonly found on the crops. The presence of aphids on the plants was affected by the predominant environmental conditions like temperature, humidity, the chemical components of the host plants and the interactions between these factors. Additionally, we identified one type of predator belonging to the order of Coleoptera, the seven-spotted ladybug (Coccinella septempunctata), which was observed to be affected by the pest density. Aphids are a major pest of wheat in Iraq and they can cause significant losses of crops if their population is not controlled.

Diversity of culturable gut bacteria in natural aphid populations and their contribution to insecticide degradation

Microorganisms in insects play pivotal roles in various aspects, including nutrition, development, protection, physiology, and behavior. Aphids, a distinct group of insects that feed on plant sap, have been the focus of research exploring the intricate relationships between microbes and insects. While extensive investigations have delved into the obligate endosymbionts in aphids, there remains a gap in understanding the diversity of gut microbes and other associated microorganisms. This study employed culture-dependent methods to isolate microorganisms from diverse aphid species (Aphis gossypii, A. nerii, A. craccivora, Hysteroneura setariae, and Myzus persicae). The results identified three bacterial phyla (Firmicutes, Proteobacteria, Actinobacteria), belonging to families such as Bacillaceae, Corynebacteriaceae, Micrococcaceae, Morganellaceae, Staphylococcaceae, and Xanthomonadaceae. Bacillus emerged as the predominant taxon, with Aphis craccivora exhibiting both high abundance and an even distribution of bacteria. Both A. craccivora and A. gossypii displayed a diverse array of bacterial species, with A. gossypii exhibiting the highest dominance index. Hysteroneura setariae showcased a diverse dominance of bacteria among aphids. Notably, the microorganisms Exiguobacterium indicum MPB-2 and Pseudomonas hibiscicola CCF 2-2 demonstrated the ability to degrade imidacloprid at a rate of 18–22%. This finding emphasizes their capacity to utilize insecticides as sole sources of carbon and nitrogen, ultimately benefiting the fitness of the insects. This study contributes to our understanding of the microorganisms presented in aphids. Highlighting the efficacy of culture-dependent methods in unveiling the diversity of these microscopic organisms.