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Aphids (Hemiptera: Aphididae) are known for their remarkable adaptability and diversity, with most species richness found in temperate regions and worldwide distribution. Climate change is expected to affect aphid populations, especially their overwintering success. In this study, we aimed to investigate the diversity of wheat aphid populations and dynamics of overwintering success of aphids across early to late sown wheat. We employed both morphological and molecular techniques to distinguish and characterize six aphid species: Rhopalosiphum maidis, Rhopalosiphum rufiabdominalis, Rhopalosiphum padi, Sitobion avenae, Schizaphis graminum, and Metopolophium dirhodum. Among these, Rhopalosiphum maidis and Rhopalosiphum rufiabdominalis found to affect at the vegetative stage of the crop, while the other species were found to affect at the reproductive stage. Notably, we observed that aphid populations were more abundant on early-sown genotypes and decreased with normal and late sowing dates. The differences in peak aphid populations among different sowing dates revealed that delayed in sowing dates minimize aphid attack by producing asynchrony between host plant and the aphid population. Conversely, the environmental factors such as temperature, relative humidity, rainfall and bright sunshine hours varied across the sowing dates where early sown wheat genotypes are exposed to lower temperatures at vegetative stage and late sown genotypes are susceptible to higher temperatures at the terminal stage. These changes in environmental factors across different sowing dates affected the timing and duration of aphid life stages, including overwintering success. Nevertheless, understanding the diversity and distribution of aphid species in wheat crop and its response to different sowing dates could be crucial for developing effective pest management strategies, particularly in the context of climate change. Overall, this study highlights the need for ongoing aphid monitoring and adaptive management approaches that account for the dynamic interactions between pests, crops and the environment. [ABSTRACT FROM AUTHOR]

The water lily aphid, Rhopalosiphum nymphaeae, is the only known aphid that can live in both terrestrial and aquatic conditions. In this study, the complete mitochondrial genome of R. nymphaeae was generated using Illumina sequencing technology. The typical circular DNA mitochondrial genome of R. nymphaeae is 15,772 bp in length, with a high A+T content (84.34%). It contains 37 coding genes (13 protein-coding genes, 22 transport RNAs, and two ribosomal RNAs) and two non-coding regions (one control region and one repeat region). Enc-plot, PR2-bias, and neutrality plot analysis indicated that the codon usage of the protein-coding genes is mainly affected by natural selection. The evolution rate analysis (the ratio of nonsynonymous to synonymous, Ka/Ks) indicated that all the PCGs in R. nymphaeae are under a strong purifying selection. The control region has conserved structure elements, and two types of tandem repeat units exist. The length and sequence of the aphid-unique repeat region has high similarity with closely related species. Phylogenetic analyses determined by both maximum likelihood and Bayesian inference support the monophyly of Aphidinae, Aphidini, Aphidina, and Rhopalosiphina. However, the monophyly of the genera in Rhopalosiphina, such as Rhopalosiphum, is still not resolved. This study may help us to understand the phylogenetic relationship of aphids, and much more aphid data are needed in future studies. [ABSTRACT FROM AUTHOR]

The compound 1,3-diphenyl-1H-pyrazole-4-carbaldehyde (1) was utilized as a fundamental component in the synthesis of novel N-phenyl pyrazole derivatives. Substituted N-phenyl pyrazole compounds including 2-cyano-3-(1,3-diphenyl-1H-pyrazol-4-yl)-N-Substituted-acrylamide derivatives (4a–h), 4-(hydrazineylidenemethyl)-1,3-diphenyl-1H-pyrazole (6) and 2-cyano-N'-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-acetohydrazide (11) were obtained in moderate yields through the reaction of 1 with 2-cyano-N-substituted acetamide derivatives 3a–h, hydrazine hydrate, and cyanoacetohydrazide under basic-catalyzed conditions, respectively. Moreover, hydrazinyl-pyarzole 6 reacted with 4,5,6,7-tetrabromoisobenzofuran-1,3-dione (7) to afford 4,5,6,7-tetrabromo-2-(((1,3-diphenyl-1H-pyrazol-4-yl)methylene)amino)- isoindoline-1,3-dione (8). Furthermore, pyrazoloacetohydrazide 11 is condensed with salicylaldehyde derivatives 12a–e to give pyrazolochromene carbohydrazide derivatives 13a–e. Also, acetohydrazide 11 refluxed with N, N-dimethylformamide dimethyl acetal to produce 2-cyano-3-(dimethylamino)-N'-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)acrylohydrazide (15), which upon exposure to acidic conditions underwent cyclization to form 4-((dimethylamino)methylene)-6-(1,3-diphenyl-1H-pyrazol-4-yl)pyridazine-3,5(4H,6H)-dione (16). The newly synthesized compounds were identified and confirmed using elemental and spectral data analyses as IR, MS, 1H NMR, 13C NMR, and 2D NMR analysis (H-H COSY, HSQC, HMBC, and NOSEY), Also, DFT studies were done to prove the geometrical optimization and spatial distributions orbitals of compounds 4a and 11. The toxicity of N-phenylpyrazole compounds was tested against the corn leaf aphid (Rhopalosiphum maidis) and the mealy plum aphid (Hyalopterus pruni). Compounds 4c, 13c, and 13d were found to be the most potent to control the two insects compared with acetamiprid 20% SP recommended by the Ministry of Agriculture. The biochemical investigation of insects was studied to the most effective compounds on insects as well, and the toxicity of compounds 4c, 13c, and 13d was studied on the predators (Hippodamia variegata, Cydonia vicina isis, Cydonia vicina nilotica, and 4th instar larvae H. variegata) under laboratory conditions. [ABSTRACT FROM AUTHOR]

Herbivory by insects leads to changes in both primary and secondary plant metabolism, ultimately impacting subsequent interactions. Some phloem‐feeding insects have developed mechanisms to suppress herbivore‐induced plant defences and manipulate the quality of host phloem sap, thereby facilitating their establishment on the host plant. Based on evidence that the specialized phloem‐feeding insects, Dalbulus maidis and Rhopalosiphum maidis, can suppress herbivore‐induced defences in maize, we hypothesized that infestation by either of these pests in maize would facilitate the colonization and establishment of subsequent conspecific and heterospecific individuals. We conducted a series of behavioural assays with these insects in both laboratory and greenhouse settings.The corn leafhopper D. maidis preferred previously infested plants as hosts, but it did not discriminate between conspecific‐ or heterospecific‐infested plants for colonization. However, when selecting a host for oviposition, it preferred depositing eggs on conspecific‐infested plants, which were the hosts that the offspring performed better compared to both non‐infested and heterospecific‐infested plants.The corn aphid R. maidis also preferred previously infested plants over non‐infested plants as hosts. However, the aphid preferred heterospecific‐infested over conspecific‐infested plants, even though heterospecific‐infested plants were hosts of lower quality to aphids. Aphids performed better on conspecific‐infested plants, followed by heterospecific‐infested plants, when compared to non‐infested plants.Our results confirm that previous colonization by the specialized phloem‐feeding insects facilitates subsequent infestations by conspecifics and heterospecifics. However, the facilitation for heterospecifics was asymmetric, as colonization by D. maidis facilitated infestations by R. maidis more than the reverse sequence of infestation. [ABSTRACT FROM AUTHOR]

Survey and population densities of aphidophagous syrphid predators and their insect hyperparasitoids on maize plants infesting with aphids namely, Rhopalosiphum maidis (Fitch) and Rhopalosiphum padi (Linnaeus) at El-Deeb village, Abou-Kbeer district, Sharkia Governorate, Egypt were studied during 2022 and 2023 seasons. The obtained results were summarized as follow: six species of aphidophagous syrphid belonging to family Syrphidae namely, Xanthogramma aegyptium Wied., Sphaerophoria flavicauda Zett., Paragus aegyptius Macq., Paragus spp., Metasyrphus (=Syrphus) corollae (Fabr.) and Scaeva albomaculata Macq were surveyed on maize plants infesting with aphids. The total relative densities of the syrphid species were 34.17, 23.92, 18.54, 10.36, 7.22 and 5.79 % of the total number of hoverfly, successively. The total numbers of aphidophagous syrphid predators were fluctuated, showing a distinct peaks of 343 and 371 predators/sample in the 2nd and 3rd weeks of August during the first and second seasons, consecutively. The highest total monthly counts of 1016 and 1299 predators recorded in August during two successive seasons 2022 and 2023, consecutively. The means of syrphids : prey ratio were 1 : 28.76 and 1 : 22.59 during two successive seasons. Five species of hyperparasitoids belong to four families were recorded parasitized on syrphid species namely, Telenomus acrobats Giard, Telenomus sp. (Scelionidae), Diplazon laetatorius (Fabricius) (Ichneumonidae), Syrphophagus aphidivorus (Mayr) (Encyrtidae) and Tetrastichus sp. (Eulophidae), represented 25.43, 16.38, 25.43, 19.62 and 13.14% of the total collected hyperparasitoids, successively. The fluctuations of the total parasitoidism percentages recorded one and two peaks of activity during the first and second seasons, respectively. The mean percentages of parasitoidism during the second season was relatively low, 17.65 % in comparison with that in the first one (21.67%). The correlations between the total numbers of aphidophagous syrphid species and percentages of parasitodism were positive significant during two successive seasons. The periodic mean temperature and relative humidity affected syrphid species population by 55.27 and 62.57% during the 1st and 2nd seasons, respectively. Temperature and relative humidity affected percentages of parasitodism by 51.19 and 47.34 during the 1st and 2nd seasons, consecutively. Generally, the pesticides are not the only ones that affect on aphidophagous syrphid predators but the hyperparasitoids decrease the total numbers of the predators and negatively or harmfully affect their role in the biological control of aphid species in open felids and greenhouses. [ABSTRACT FROM AUTHOR]

Simple Summary: The aphid species Rhopalosiphum nymphaeae is a highly polyphagous pest that poses a significant threat to global agriculture. Biological control using natural enemies, such as the harlequin ladybird (Harmonia axyridis), is important for managing this pest. Our study evaluated the predation ability of H. axyridis in controlling R. nymphaeae. We examined the functional and numerical response of larva and adult H. axyridis preying on R. nymphaeae. Our results showed that the predation rate of individual H. axyridis on R. nymphaeae nymphs significantly increased as prey density increased. It was noted that fourth instar and adult H. axyridis were identified as optimal developmental stages in controlling R. nymphaeae. In addition, variations in intraspecific interference and self-interference exhibited by H. axyridis under increasing predator density were observed. The water lily aphid (Rhopalosiphum nymphaeae) is a highly polyphagous herbivore that causes severe damage to many terrestrial and aquatic plants, especially lotus. Due to environmental concerns about water pollution and other issues caused by chemical control methods, there is an urgent need to develop effective and sustainable control methods. The harlequin ladybird (Harmonia axyridis) is a well-known aphid predator and may pose a potential threat to R. nymphaeae. To study the predation ability of H. axyridis at different developmental stages on R. nymphaeae, we assessed the functional response, attack rate, and search effect of H. axyridis larvae and adults preying on R. nymphaeae. The numerical response of this process was also evaluated under a constant ladybird-to-aphid ratio and constant aphid density conditions, respectively. Our results showed that all predator stages exhibited type II functional responses. The predation rate of individual H. axyridis on R. nymphaeae nymphs significantly increased as prey density increased. In contrast, the search effect of H. axyridis gradually decreased with an increase in prey density. Meanwhile, H. axyridis at different developmental stages possess varying predation abilities; fourth instar and adult H. axyridis were found to be highly efficient predators of R. nymphaeae. H. axyridis adults exhibited the highest predation ability and predation rate, while both the adult and fourth-instar larvae exhibited the highest attack rate. Moreover, fourth-instar larvae exhibited the highest search effect value at initially lower prey densities, although adults surpassed them at higher prey densities. Our results also indicated that H. axyridis exhibited varying degrees of intraspecific interference and self-interference influence as predator density increases. These results strongly support H. axyridis as an effective biocontrol agent for R. nymphaeae. [ABSTRACT FROM AUTHOR]

Rhopalosiphum maidis Fitch, 1856 is widespread in tropical and temperate regions. R. maidis can spread viral diseases in maize and harm various important crops. In the present study, we report the first complete mitochondrial genome of R. maidis. The circular genome is found to be 17,021 bp in length, includes a standard set of 22 transfer RNAs, two ribosomal RNAs, 13 protein-coding genes, and two non-coding control regions. The base composition is 84.32% AT and 15.79% GC. The phylogenetic tree of the 17 Aphidini families constructed based on the nucleotide sequences of complete mitochondrial genomes strongly supports the conclusion that R. maidis is closely related to R. rufiabdominalis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Premise: Polyploidy is a widespread mutational process in angiosperms that may alter population performance of not only plants but also their interacting species. Yet, knowledge of whether polyploidy affects plant–herbivore dynamics is scarce. Here, we tested whether aphid herbivores exhibit preference for diploid or neopolyploid plants, whether polyploidy impacts plant and herbivore performance, and whether these interactions depend on the plant genetic background. Methods: Using independently synthesized neotetraploid strains paired with their diploid progenitors of greater duckweed (Spirodela polyrhiza), we evaluated the effect of neopolyploidy on duckweed's interaction with the water‐lily aphid (Rhopalosiphum nymphaeae). Using paired‐choice experiments, we evaluated feeding preference of the herbivore. We then evaluated the consequences of polyploidy on aphid and plant performance by measuring population growth over multiple generations. Results: Aphids preferred neopolyploids when plants were provided at equal abundances but not at equal surface areas, suggesting the role of plant population surface area in driving this preference. Additionally, neopolyploidy increased aphid population performance, but this result was dependent on the plant's genetic lineage. Lastly, the impact of herbivory on neopolyploid vs. diploid duckweed varied greatly with genetic lineage, where neopolyploids appeared to be variably tolerant compared to diploids, sometimes mirroring the effect on herbivore performance. Conclusions: By experimentally testing the impacts of polyploidy on trophic species interactions, we showed that polyploidization can impact the preference and performance of herbivores on their plant hosts. These results have significant implications for the establishment and persistence of plants and herbivores in the face of plant polyploidy. [ABSTRACT FROM AUTHOR]

Extensive surveys were undertaken across Kerala during 2018-22, to explore the diversity of aphid fauna associated with different flora. The study recorded 25 species of aphids under 17 genera in four tribes belonging to four subfamilies of Aphididae. Aphidinae was the predominant subfamily, followed by Greenideinae, Hormaphidinae and Eriosomatinae. Aphidinae was represented by two tribes, Aphidini and Macrosiphini. The tribes Aphidini (Aphis(L.), Rhopalosiphum Koch, Hysteroneura Davis and Melanaphis van der Goot) and Macrosiphini (Pentalonia Coquerel, Brevicoryne van der Goot, Macrosiphoniella del Guercio, Macrosiphum Passerini, Metopolophium Mordvilko, Acyrthosiphon Mordvilko, Uroleucon Mordvilko and Aulacorthum Mordvilko) were represented by four and eight genera, respectively. The subfamily Greenideinae was represented by two genera in a single tribe (Greenideini); Hormaphidinae represented by two genera in a single tribe (Cerataphidini), while only one genus in a single tribe (Eriosomatini) was recorded in the subfamily Eriosomatinae. The genus Aphis was the most diverse with five species. Aphis gossypii Glover exhibited a wider host range with 20 host plants. The study records new distribution of three aphid species from south India and seven species from Kerala. [ABSTRACT FROM AUTHOR]

The study was conducted to identify novel simple sequence repeat (SSR) markers associated with resistance to corn aphid (CLA), Rhopalosiphum maidis L. in 48 selected bread wheat (Triticum aestivum L.) and wild wheat (Aegilops spp. & T. dicoccoides) genotypes during two consecutive cropping seasons (2018–19 and 2019–20). A total of 51 polymorphic markers containing 143 alleles were used for the analysis. The frequency of the major allele ranged from 0.552 (Xgwm113) to 0.938 (Xcfd45, Xgwm194 and Xgwm526), with a mean of 0.731. Gene diversity ranged from 0.116 (Xgwm526) to 0.489 (Xgwm113), with a mean of 0.354. The polymorphic information content (PIC) value for the SSR markers ranged from 0.107 (Xgwm526) to 0.370 (Xgwm113) with a mean of 0.282. The results of the STRUCTURE analysis revealed the presence of four main subgroups in the populations. Analysis of molecular variance (AMOVA) showed that the between-group difference was around 37 per cent of the total variation contributed to the diversity by the whole germplasm, while 63 per cent of the variation was attributed between individuals within the group. A general linear model (GLM) was used to identify marker-trait associations, which detected a total of 23 and 27 significant new marker-trait associations (MTAs) at the p < 0.01 significance level during the 2018–19 and 2019–20 crop seasons, respectively. The findings of this study have important implications for the identification of molecular markers associated with CLA resistance. These markers can increase the accuracy and efficiency of aphid-resistant germplasm selection, ultimately facilitating the transfer of resistance traits to desirable wheat genotypes. [ABSTRACT FROM AUTHOR]

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The present investigation was conducted on aphid complex at the Post Graduate experimental field of Department of Agricultural Entomology, College of Agriculture, Campus Latur, during 2020-21. The results revealed that the aphid Melanaphis sacchari reached its maximum in 4th SMW (166.66 aphids / plant). Correlation coefficients revealed that none of the weather parameters had significant effect on M. sacchari . Rhopalosiphum maidis reached its peak incidence in 5th SMW (40 aphids/ plant). Correlation studies revealed that the before noon relative humidity correlated positively, while wind speed correlated negatively with incidence of R. maidis. [ABSTRACT FROM AUTHOR]

Water lily aphid Rhopalosiphum nymphaeae L. (Hemiptera: Aphididae) is the major pest of Makhana/Gorgon nut Euryale ferox Salisb, which is an important aquatic crop of tropical and subtropical regions of South-East and East Asia. The basic information such as distribution pattern and optimum sample size for estimating population density in the field is unknown. Therefore, we studied spatial distribution patterns for two stages, i.e., nymphs and adults of R. nymphaeae, using five different distribution indices and two regression methods viz., Taylor's power law and Iwao's mean crowding index for two years. All the indices showed aggregated distribution by nymphs and adults of R. nymphaeae in both years individually and with the pooled data of two years. The values of aggregation parameter (b) of Taylor's power law and density contagiousness coefficient (β) of Iwao's mean crowding index were found to be more than one for both nymphs and adults for each of the years, and pooled data of two years indicated an aggregated distribution of the R. nymphaeae. The optimal sample size (n) was estimated at three fixed precision levels of 0.05, 0.10, and 0.25 with Iwao's regression coefficients. The results showed that the optimum sample size decreased with increased levels of precision and mean aphid density. The optimum sample size (n) for estimating the lowest (3.3/leaf) and highest density (217.6/leaf) of both nymphs and adults ranged from 305.2 to 26.3, 76.3 to 6.6, and 12.2 to 1.0 with 5, 10 and 25% levels of precision. This basic information on spatial distribution pattern and optimum sample size helps monitor and formulate effective management strategies against R. nymphaeae. [ABSTRACT FROM AUTHOR]

The aphid Rhopalosiphum maidis is a serious pest against cereal plants. In Egypt, it causes serious damage to many cereal plants. The principal idea of this study was achieved based on the observation of various seasonal invasion rates of this pest on different host plants suggesting climatic adaptation by R. maidis polymorphs. The invasion rates on winter plants were higher than those of summer. Morphologically, all collections were belonging to R. maidis. The authors assumed that different biotypes of R. maidis are present in the studied area. To address this hypothesis, the mitochondrial cytochrome oxidase I (COI) gene was amplified in aphids collected from wheat, barley, sorghum and maize in Assiut, Egypt. Polymerase chain reactions (PCR) identified 687 bps products corresponding to a partial sequence of (COI). Multiple sequence alignment of the sequenced products revealed that at least five haplotypes are present on the tested plants. Phylogenetic analysis using the neighbor-joining method identified five clades that represent different biotypes. The identified clades contained mixtures between summer and winter R. maidis collections suggesting that different biotypes are present in mixtures on the same plant. Our findings showed that R. maidis develops different polymorphs on various host plants at different climatic conditions. [ABSTRACT FROM AUTHOR]

Corn-leaf aphid (CLA-Rhopalosiphum maidis) is a major insect pest of barley (Hordeum vulgare) causing yield loss upto 30% under severe infestation. Keeping in view of the availability of very few sources of CLA resistance in barley, the present investigation was framed to assess the genetic diversity and population structure of 43 wild barley (H. vulgare subsp. spontaneum) genotypes using eight microsatellite markers against R. maidis. Three statistical methods viz. multivariate-hierarchical clustering, Bayesian clustering and PCoA, unanimously grouped genotypes into three subpopulations (K = 3) with 25.58% (SubPop1-Red), 39.53% (SubPop2-Green) and 34.88% (SubPop3-Blue) genotypes including admixtures. Based on Q ≥ 66.66%, 37.20% genotypes formed a superficial "Mixed/Admixture" subpopulation. All polymorphic SSR markers generated 36 alleles, averaging to 4.5 alleles/locus (2–7 range). The PIC and H were highest in MS31 and lowest in MS28, with averages of 0.66 and 0.71. MAF and mean genetic diversity were 0.16 and 89.28%, respectively. All these parameters indicated the presence of predominant genetic diversity and population structure amongst the studied genotypes. Based on AII, only 6 genotypes were found to be R. maidis resistant. SubPop3 had 91.66% (11) of the resistant or moderately resistant genotypes. SubPop3 also had the most pure genotypes (11), the least aphid infestation (8.78), and the highest GS (0.88), indicating its suitability for future R. maidis resistance breeding initiatives. [ABSTRACT FROM AUTHOR]

Corn-leaf aphid (CLA), Rhopalosiphum maidis (Fitch) (Hemiptera: Aphididae) is a serious economic pest of barley worldwide. Breeding for aphid resistance in plants is considered a cost-effective and environmentally safe approach for aphid control, compared to the use of chemical pesticides. One of the challenges in breeding for aphid resistance is the identification of resistant plant genotypes, which can be achieved through the use of molecular markers. In the present study, a set of aphid specific 10 simple-sequence repeats (SSR) markers were used to investigate genetic diversity and population structure analyses in 109 barley genotypes against R. maidis. Three statistical methods viz., multivariate hierarchical clustering based on Jaccard's similarity coefficient, principal coordinate analysis (PCoA) and the Bayesian approach were utilized to classify the 109 barley genotypes. The analyses revealed four subpopulations i.e., SubPop1, SubPop2, SubPop3 and SubPop4 with 19, 46, 20 and 24 genotypes including admixtures, respectively and represented 17.43%, 42.2%, 18.34% and 22.01% genotypes of the total population size, respectively. The studied SSR markers produced 67 polymorphic bands, with an average of 6.7 and ranging from 3 to 12 bands. Heterozygosity (H) was found to be highest in SSR28 (0.64) and lowest in SSR27 (0.89). The observed genetic diversity index varied from 0.10 to 0.34 (with an average of 0.19). Major allele frequency varied from 74.08% to 94.80%. On an average, 87.52% of the 109 barley genotypes shared a common major allele at any locus. Based on the Aphid Infestation Index (AII), only 2 genotypes were found to be resistant against CLA. SubPop2 also had lowest mean aphid population (28.83), widest genetic similarity index (0.60-1.00) and highest genetic similarity coefficient (0.82), which highlighted its potential for inclusion in future CLA resistance breeding programs. [ABSTRACT FROM AUTHOR]

The percentage of parasitism of Rhopalosiphum maidis Fitch was determined in maize (Zea mays L.) leaves inspected in the field, and its parasitoids were obtained. The percentage of parasitism increased by about 1.5% daily and in the first week of April, it exceeded 70%. Lysiphlebus testaceipes Cresson was the dominant parasitoid of R. maidis (84.2%), with Aphidius smithi Sharma & Subba Rao (4.0%), several Eurytomidae (2.9%), and Figitidae specimens (1.0%). [ABSTRACT FROM AUTHOR]

Simple Summary: Pests are largely responsible for the loss of agricultural crops, so the search for new pesticides for their control is indispensable. The irrational use of synthetic products has affected human health and the environment, and has generated resistance, which is why the use of natural products could be a safer alternative. In this study, the formulation of a nanoemulsion was carried out to provide greater stability to the botanical compound 1,8-cineole, whose pesticidal effect is documented; however, it is not used due to its high volatility. The pesticidal effect of this nanoemulsion was also evaluated against the pests known as two-spotted spider mite, corn aphid and silverleaf whitefly. Nanotransport systems such as nanoemulsions allows for the field application of molecules that are chemically unstable on their own, such as monoterpenoids. With this study it was possible to determine that these nanoemulsion systems favor the release of the active compound in laboratory tests, increasing the mortality rate of the three pests. This allows for proposing this nanoemulsion as a potential botanical pesticide product against agricultural arthropod pests. Pest control is a main concern in agriculture. Indiscriminate application of synthetic pesticides has caused negative impacts leading to the rapid development of resistance in arthropod pests. Plant secondary metabolites have been proposed as a safer alternative to conventional pesticides. Monoterpenoids have reported bioactivities against important pests; however, due to their high volatility, low water solubility and chemical instability, the application of these compounds has been limited. Nanosystems represent a potential vehicle for the broad application of monoterpenoids. In this study, an 1,8-cineole nanoemulsion was prepared by the low energy method of phase inversion, characterization of droplet size distribution and polydispersity index (PDI) was carried out by dynamic light scattering and stability was evaluated by centrifugation and Turbiscan analysis. Fumigant bioactivity was evaluated against Tetranychus urticae, Rhopalosiphum maidis and Bemisia tabaci. A nanoemulsion with oil:surfactant:water ratio of 0.5:1:8.5 had a droplet size of 14.7 nm and PDI of 0.178. Formulation was stable after centrifugation and the Turbiscan analysis showed no particle migration and a delta backscattering of ±1%. Nanoemulsion exhibited around 50% more bioactivity as a fumigant on arthropods when compared to free monoterpenoid. These results suggest that nanoformulations can provide volatile compounds of protection against volatilization, improving their bioactivity. [ABSTRACT FROM AUTHOR]

Simple Summary: Cotton leafroll dwarf virus (CLRDV) is capable of causing yield loss in cotton. Eight species of aphids have been reported to feed on cotton, but Aphis gossypii is the only known CLRDV vector in the United States (U.S.). Little is known about their distribution, abundance, and seasonal dynamics in the southern U.S. The epidemiological value of understanding this prompted a two-year study to monitor the populations of aphids that infest cotton fields throughout the southern U.S., where CLRDV has been reported. Aphis gossypii and Protaphis middletonii were the most abundant aphid species collected. Aphis craccivora, Macrosiphum euphorbiae, Myzus persicae, Rhopalosiphum rufiabdominale, and Smynthurodes betae were also detected in this study; however, their populations remained consistently low throughout the collection period. Results from this study presented novel information regarding the seasonal variation of the species and populations of aphids associated with cotton in the region. Cotton leafroll dwarf virus (CLRDV) is an emerging aphid-borne pathogen infecting cotton, Gossypium hirsutum L., in the southern United States (U.S.). The cotton aphid, Aphis gossypii Glover, infests cotton annually and is the only known vector to transmit CLRDV to cotton. Seven other species have been reported to feed on, but not often infest, cotton: Protaphis middletonii Thomas, Aphis craccivora Koch, Aphis fabae Scopoli, Macrosiphum euphorbiae Thomas, Myzus persicae Sulzer, Rhopalosiphum rufiabdominale Sasaki, and Smynthurodes betae Westwood. These seven have not been studied in cotton, but due to their potential epidemiological importance, an understanding of the intra- and inter-annual variations of these species is needed. In 2020 and 2021, aphids were monitored from North Carolina to Texas using pan traps around cotton fields. All of the species known to infest cotton, excluding A. fabae, were detected in this study. Protaphis middletonii and A. gossypii were the most abundant species identified. The five other species of aphids captured were consistently low throughout the study and, with the exception of R. rufiabdominale, were not detected at all locations. The abundance, distribution, and seasonal dynamics of cotton-infesting aphids across the southern U.S. are discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Cotton leafroll dwarf virus (CLRDV) can cause yield loss of cotton in susceptible plants. The only known aphid vector in the U.S. is Aphis gossypii, which regularly infests cotton, but knowledge so far is limited to the cotton growing season. Seven other species are also known to feed on cotton, but little is known about their seasonal dynamics. Two species are known vectors of CLRDV in chickpea in India. Improving our understanding of the viral spread and seasonal dynamics of potential vectors is key to developing management strategies for plant pathogens. In this study, we monitored seasonal population dynamics of these eight species, in three locations and two different habitats in Alabama, with the use of pan traps, year-round, for two consecutive years. To coordinate this with viral presence, CLRDV spread was monitored at the same sites with the use of cotton sentinel plants. Plants (while conditions allowed) and traps were collected and replaced weekly. Our findings provided baseline information on when these eight species are dispersing in the landscape and when CLRDV spread is occurring in cotton. While A. gossypii is likely the primary vector, early season spread of CLRDV suggests additional aphid vectors are possible. Cotton leafroll dwarf virus (CLRDV) is an introduced Polerovirus (Family: Solemoviridae) of cotton, Gossypium hirsutum L., in the U.S. The only vector known to transmit this virus to cotton is the cotton aphid, Aphis gossypii Glover; however, there are seven other species of aphids (Hemiptera: Aphididae) reported to colonize cotton in the southeastern U.S.: Protaphis middletonii (Thomas), Rhopalosiphum rufiabdominale (Sasaki), Aphis craccivora Koch, Macrosiphum euphorbiae Thomas, Myzus persicae (Sulzer), Smythurodes betae Westwood, and Aphis fabae Scopoli. Little to no information is available on annual population dynamics of these species in the southeastern U.S. The timing of CLRDV spread to cotton plantings is also unknown. The objective of this study was to monitor the population dynamics of eight cotton-feeding aphid species concurrent with the spread of CLRDV at three different locations in Alabama. Aphids were monitored weekly for two years with yellow pan traps, and sentinel plants were deployed weekly to monitor CLRDV spread throughout the cotton-growing season. During the two years, most CLRDV spread at all locations occurred when A. gossypii was actively dispersing in the field. Early season spread at sites in south and central Alabama, when A. gossypii was not abundant, suggests additional aphid vectors are possible. [ABSTRACT FROM AUTHOR]

The corn leaf aphid (Rhopalosiphum maidis) is a major maize pest that frequently causes substantial yield losses. Exploring the genetic basis of resistance to aphids is important for improving maize yield and quality. Here, we used a maize recombinant inbred line population derived from two parents with different susceptibility to aphids, B73 (susceptible) and Abe2 (resistant), and performed quantitative trait locus (QTL) mapping using aphid resistance scores as an indicator. We mapped a stable QTL, qRTA6 , to chromosome 6 using data from 2 years of field trials, which explained 40.12–55.17% of the phenotypic variation. To further investigate the mechanism of aphid resistance in Abe2, we constructed transcriptome and metabolome libraries from Abe2 and B73 leaves with or without aphid infestation at different time points. Integrating QTL mapping and transcriptome data revealed three aphid resistance candidate genes (Zm00001d035736, Zm00001d035751, and Zm00001d035767) associated with the hypersensitive response, the jasmonic acid pathway, and protein ubiquitination. Integrated transcriptomic and metabolomic analysis revealed that the differentially expressed genes and metabolites were enriched in flavonoid biosynthesis. These findings extend our understanding of the molecular mechanisms controlling aphid resistance in maize, and the QTL and candidate genes are valuable resources for increasing this resistance. [ABSTRACT FROM AUTHOR]

A mapping population, recombinant inbred lines (RILs), was developed from the cross of aphid susceptible cv. PL426 and resistant genotype BK 9816 to identify genetic loci conferring corn leaf aphid (CLA) Rhopalosiphum maidis (Fitch) resistance in barley. RILs showed wide range of aphid infestation (2.2–65.0 aphids/tiller) indicating quantitative inheritance of aphid resistance. All the traits related to aphid resistance, viz. aphid fecundity, chlorophyll content and tiller dry weight of plants, also showed quantitative variation. RILs were further genotyped by sequencing to identify SNPs covering whole barley genome. A total of 605 high-quality bin-mapped SNPs were positioned in seven linkage groups with a total map length of 1208.9 cM and average marker distance of 2.02 cM. Composite interval mapping identified five different quantitative trait loci (QTLs) on chromosomes 1H, 3H, 5H and 6H associated with aphid resistance and related traits. Two QTLs on chromosome 6H, QCLA.pau-6H.1 and QCLA.pau-6H.2, were mapped at genetic intervals of 1.7 cM and 4.9 cM, respectively. QCLA.pau-6H.1 explained 9.76 percent of phenotypic variation for aphid count and 12.78 percent for aphid score. Similarly, QCLA.pau-6H.2 explained 10.96 percent of phenotypic variation for aphid score. The QTL for chlorophyll content and tiller dry weight spanned the same region of QCLA.pau-6H.2, explained 13.08 and 13.20 percent phenotypic variation, respectively. Another QTL associated with chlorophyll content was mapped on chromosome 3H at 3.6-cM interval explained 12.90 percent phenotypic variation. In addition, QTL regions were also identified for aphid resistance and related traits on chromosome 1H and 5H. [ABSTRACT FROM AUTHOR]

The black bean aphid Aphis fabae (Hemiptera: Aphididae), the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) and the corn leaf aphid Rhopalosiphum maidis (Hemiptera: Aphididae) are three pests that causes significant economic losses, to several crops, in particular faba bean (Vicia faba), stored products, and maize (Zea mays) respectively. In order to search for readily biodegradable and eco-friendly insecticides, this study aimed to evaluate the efficacy of Lemon verbena Aloysia citrodora (Verbenaceae) essential oil fumigant toxicity against these three pests and identify its chemical composition by gas chromatography–mass spectrometry (GC–MS). The major compounds were Citral (13.80%), D- limonene, (12.16%), Neral (10.67%), Bicyclogermacrene (10.03%), Isospathulenol (6.06%), caryophyllene oxide (5.63%) and p-cymene (4.5%). Significant differences in insect mortality to essential oil vapor were identified in the fumigant toxicity at 48 h exposure time; A. citrodora oil showed higher toxicity on A. fabae (LC50 = 0.011 µl/l air), compared to R. maidis (LC50 = 0.021 µl/l air), followed by T. castaneum (LC50 = 1.149 µl/l air). The present study indicates that A. citrodora essential oil could be employed as a potential insecticide against aphis fabae, Rhopalosiphum maidis and Tribolium castaneum. [ABSTRACT FROM AUTHOR]

Plant extracts are a great source of molecules with insecticidal activity and are used to control pests in various crop production systems. In this study, we evaluated the aphidicidal properties in vitro of the n-hexane extract of leaves of castor-bean (Ricinus communis L.; Euphorbiaceae) at different concentrations (0.5, 1.0, 2.5, 5.0 and 10 kg m-3) against apterous adults of corn leaf aphid (Rhopalosiphum maidis Fitch) and the yellow sugarcane aphid (Sipha flava Forbes). The observed effects were dose-dependent, and the highest concentration evaluated (10 kg m-3) caused 82% mortality in R. maidis and 79% in S. flava. To identify chemical compounds, present in the extract we used mass gas chromatography, identifying 16 compounds. Palmitic acid was the major compound, with 45.34% abundance. The data obtained indicate the existence of insecticidal compounds in the castor-bean n-hexane extract, which could be used as an alternative bioinsecticide in the integrated management of these two aphid species. [ABSTRACT FROM AUTHOR]

El maíz, Zea mays L., es de gran importancia económica, social y cultural en México. Su agroecosistema posee insectos fitófagos y entomófagos. Se estudió la diversidad de éstos en la Comarca Lagunera en 2020 y 2021. Se identificaron 38 especies de insectos entomófagos, tanto depredadores como parasitoides, siendo las más comunes Bariscapus sp., Orius leavigatus, Tetrastichus sp., Hippodamia convergens, Chrysoperla sp., y Collops vittatus. Se ha reportado que este complejo de insectos entomófagos juega un papel importante en el control biológico natural de los insectos plaga. Se encontraron 26 especies de insectos fitófagos, siendo las más comunes Chaetocnema ectypa, Diabrotica balteata, Rhopalosiphum maidis, y Dalbulus maidis. Este complejo de insectos fitófagos puede estar desempeñando un papel importante como factor limitante de la productividad del maíz o ser plagas potenciales. Con base en los valores de los índices de diversidad de Margalef, Simpson y Shannon-Wiener se encontró que la diversidad de insectos entomófagos fue más alta al principio del ciclo del cultivo; mientras que la diversidad de insectos fitófagos fue mayor de mediados a finales del mismo; de forma general se considera que la diversidad de la entomofauna en maíz fue intermedia. Maize, Zea mays L., is of great economic, social, and cultural importance in Mexico. Its agroecosystem has phytophagous and entomophagous insects. Diversity in the Comarca Lagunera was studied in 2020 and 2021. Thirty-eight species of predators and parasitoids were found, with most common being Bariscapus sp., Orius leavigatus, Tetrastichus sp., Hippodamia convergens, Chrysoperla sp., and Collops vittatus. This complex of entomophagous insects is important for natural biological control of pest insects. Twenty-six species of phytophagous insects were also found, the most common being Chaetocnema ectypa, Diabrotica balteata, Rhopalosiphum maidis, and Dalbulus maidis. This complex of phytophagous insects may be important as a limiting factor of maize productivity or be potential pests. Based on values of the diversity indices of Margalef, Simpson and Shannon-Wiener, diversity of entomophagous insects was more at the beginning of the crop-growing season, while diversity of phytophagous insects was greater mid to late; diversity of entomofauna in maize was intermediate. [ABSTRACT FROM AUTHOR]

Bacterial symbionts associated with aphids are important for their ecological fitness. The corn leaf aphid, Rhopalosiphum maidis (Fitch), is one of the most damaging aphid pests on maize and has been reported to harbor Hamiltonella defensa and Regiella insecticola while the effects of the secondary symbionts (Ssymbionts) on host ecology and primary symbiont Buchnera aphidicola remain unclear. Here, four aphid strains were established, two of which were collected from Langfang - Hebei Province, China, with similar symbiont pattern except for the presence of H. defensa. Two other aphid strains were collected from Nanning - Guangxi Province, China, with the same symbiont infection except for the presence of R. insecticola. Phylogenetic analysis and aphid genotyping indicated that the S-symbiont-infected and free aphid strains from the same location had identical genetic backgrounds. Aphid fitness measurement showed that aphid strain infected with H. defensa performed shortened developmental duration for 1st instar and total nymph stages, reduced aphid survival rate, offspring, and longevity. While the developmental duration of H-infected strains was accelerated, and the adult weight was significantly higher compared to the Hfree strain. Infection with R. insecticola did not affect the aphid's entire nymph stage duration and survival rate. As the H-strain does, aphids infected with R. insecticola also underwent a drop in offspring, along with marginally lower longevity. Unlike the H-infected strain, the R-infected strain performed delayed developmental duration and lower adult weight. The B. aphidicola titers of the Hinfected strains showed a steep drop during the aphid 1st to 3rd instar stages, while the augmentation of B. aphidicola titers was found in the R-infected strain during the aphid 1st to 3rd instar. Our study investigated for the first time the effect of the Ssymbionts on the ecology fitness and primary symbiont in R. maidis, indicating that infection with secondary symbionts leads to the modulation of aphid primary symbiont abundance, together inducing significant fitness costs on aphids with further impact on environmental adaptation and trophic interactions. [ABSTRACT FROM AUTHOR]

Simple Summary: Rhopalosiphum padi and Rhopalosiphum maidis are two common phloem-sucking pests on maize which can even transmit viruses (i.e., maize dwarf mosaic virus, MDMV) leading to severe yield losses of maize. Population genetic studies provide information about how much ecological and genetic divergence has occurred among many near and distant populations. We investigated the genetic diversity of both Rhopalosiphum aphids collected from maize in China and Europe, and we found that different populations of R. maidis showed low genetic variation, indicating a high level of gene flow of both nuclear and mitochondrial genes in this aphid. However, the mitochondrial gene of R. padi exhibited obvious genetic differentiation between Chinese samples and European samples. In conclusion, the domestic populations of both R. padi and R. maidis showed low genetic diversity, and the long distance between China and Europe may interrupt the gene exchange of aphids. Population genetic studies can reveal clues about the evolution of adaptive strategies of aphid species in agroecosystems and demonstrate the influence of environmental factors on the genetic diversity and gene flow among aphid populations. To investigate the genetic diversity of two Rhopalosiphum aphid species from different geographical regions, 32 populations (n = 535) of the bird cherry-oat aphid (Rhopalosiphum padi Linnaeus) and 38 populations (n = 808) of the corn leaf aphid (Rhopalosiphum maidis Fitch) from China and Europe were analyzed using one nuclear (elongation factor-1 alpha) and two mitochondrial (cytochrome oxidase I and II) genes. Based on the COI-COII sequencing, two obvious clades between Chinese and European populations and a low level of gene flow (Nm = 0.15) were detected in R. padi, while no geographical-associated genetic variation was found for EF-1α in this species. All genes in R. maidis had low genetic variation, indicating a high level of gene flow (Nm = 5.31 of COI-COII and Nm = 2.89 of EF-1α). Based on the mitochondrial result of R. padi, we concluded that the long distance between China and Europe may be interrupting the gene flow. The discordant results of nuclear gene analyses in R. padi may be due to the slower evolution of nuclear genes compared to mitochondrial genes. The gene exchange may occur gradually with the potential for continuous migration of the aphid. This study facilitates the design of control strategies for these pests. [ABSTRACT FROM AUTHOR]

Aphids are one of the most important insect pests of wheat crop in all wheat growing regions of the world. Amongst various aphid species, the corn leaf aphid (Rhopalosiphum maidis F.) is considered one of the most destructive insect pests of wheat in the North Western Plains region of India. Transcriptome profiling of highly susceptible wheat Triticum durum genotype, A-9-30-1 and tolerant wheat Triticum aestivum genotype, HD2967 was performed to investigate aphid-host interactions. The results obtained from differential gene expression analysis of R. maidis on the highly susceptible genotype, A-9-30-1 plants, when compared with the tolerant genotype, HD2967, showed that 212 genes were significantly upregulated and 1009 genes were significantly downregulated. Our findings demonstrated that the genes associated with defense were significantly higher in response to R. maidis on HD2967 as compared to A-9-30-1. Additionally, various genes with physiological attributes were expressed during aphid attack. Based on gene ontology classification, three classifications, such as, cellular components (CC), molecular function (MF), and biological processes (BP) of sequences were identified. KEGG enrichment analysis revealed that twenty-five pathway genes were differentially expressed during the infestation of wheat with R. maidis. Notable changes were observed in A-9-30-1 and HD2967 transcriptomic profiling after infestation. The results obtained in the present study will help to elucidate the mechanism governing host-pest interaction and may lead to the development of new methods for increasing the resistance level of wheat against R. maidis, including overexpression of defense-related genes. [ABSTRACT FROM AUTHOR]

Habitat selection is a critical process that shapes the spatial distribution of species at local and regional scales. The mechanisms underlying habitat preference rely on environmental factors, species traits, and ecological interactions with other species. Here, we examined spatial segregation between two co-occurring aphid species (Rhopalosiphum maidis and R. padi) on wheat plants. We hypothesized that spatial segregation between these aphid species was mediated by aphid cuticular compounds left as chemical "footprints" on plant surfaces. Combining field and laboratory experiments, we first examined how plant microsites alter fitness by measuring the fecundity of each species. Next, we tested whether intra- and interspecific pre-inhabitation modified habitat selection in both aphid species. Both aphid species preferred and exhibited higher fecundity on wheat stems versus leaves. Laboratory trials showed that R. maidis pre-inhabitation altered R. padi spatial preference. By gas chromatography-mass spectrometry analysis and bioassays testing the effects of aphid density and footprint extracts, we found a density-dependent response, with R. padi avoiding locations previously inhabited by R. maidis. The chemical analysis of footprint crude extracts revealed a highly abundant compound, 1-hexacosanol, and when presented in the synthetic form, also elicited R. padi displacement. Altogether, it indicated that R. maidis footprints altered R. padi habitat selection with cuticular compounds playing a relevant role in the habitat selection process in co-occurring aphid species. [ABSTRACT FROM AUTHOR]

The corn leaf aphid is considered an important pest associated with maize. This study aimed to discover the trophic associations around Rhopalosiphum maidis in Manabí, Ecuador. Maize leaves were sampled to determine the numbers of parasitized aphids, and the identities of predators and parasitoids. Nine taxa of natural enemies were detected: the primary parasitoid was Lysiphlebus testaceipes Cresson, 1880 (Hymenoptera: Braconidae); the hyperparasitoid Syrphophagus aphidivorus (Mayr, 1876) (Hymenoptera: Encyrtidae); the predatory hoverfly Ocyptamus dimidiatus (Fabricius, 1781) (Diptera: Syrphidae), four species of coccinellids, Cheilomenes sexmaculata (Fabricius, 1781), Cycloneda sanguinea (Linnaeus, 1763), Hippodamia convergens Guerin-Meneville, 1842 and Paraneda pallidula guticollis (Coleoptera: Coccinellidae) and an assassin bug, Zelus sp. (Hemiptera: Reduviidae). A parasitoid, Pachyneuron formosum Walker, 1833 (Hymenoptera: Pteromalidae) emerged from hoverfly pupae. This study reports the presence of the parasitoids S. aphidivorus and P. formosum in Ecuador for the first time. These results increase the knowledge of a four-trophic level relationship (host plant – pest – parasitoids, predators – hyperparasitoids) in a maize agroecosystem as a fundamental basis for biological control programs. [ABSTRACT FROM AUTHOR]

Infestation of the broad bean and maize crop with Aphis craccivora and Rhopalosiphum maidis, respectively at Qaha research station, Qalubyia started in January and May (or June) during two years of study. The monthly collected number and percent abundance of each and total life stage (s) of A. craccivora and R. maidis gradually increased to reach peaks in March (or March and February) and August then decreased in the last month of the season of the broad bean and maize, respectively. Immatures were the most prevalent life stages followed by unwinged and winged adult females. Generally, the total collected number of each life stage of A. craccivora and R. maidis was higher in 2018 than in 2017. A total of 26 spider species belonging to 20 genera and 10 families of order Araneae were associated with the two aphids, A. craccivora and R. maidis, on the broad bean and maize at the site of study in 2017 and 2018. About 50% of the collected species were common spiders associated with each of the two aphid species on its host crop. Generally, the total spiders of the collected families on the broad bean and maize crops started appearing with relatively small numbers in January and May, gradually increased in parallel with those of the associated aphid species to reach peaks in March and August, then the numbers of both were decreased at the end of the crop season in April and September, respectively during each year of the study. [ABSTRACT FROM AUTHOR]

The water lily aphid is a cosmopolitan species that feeds on various plants. Its primary hosts are Prunus species from which they migrate to their secondary hosts - aquatic and semi-aquatic plants. So far, in Serbia, Rhopalosiphum nymphaeae is recorded to attack only three plant species as secondary hosts. In our study, conducted in September 2020, we have researched the association of water lily aphid with secondary hosts in wetland habitats. A total of 44 samples were collected from 16 localities. In addition to the plant species previously reported, in this study 11 secondary hosts are documented for the first time in Serbia. The most common trophic association of R. nymphaeae was with Salvinia natans which was registered in 13 localities. There is a high possibility of finding new records of secondary hosts, therefore, more research is needed to complete the information about the water lily aphid and its hosts in Serbia. [ABSTRACT FROM AUTHOR]

In this study, different maize fields cultivated under different management systems were sampled to test corn leaf aphid, Rhopalosiphum maidis, populations in terms of total and endosymbiotic bacterial diversity. Corn leaf aphid natural populations were collected from traditionally managed maize fields grown under high agricultural and natural landscape diversity as well as conventionally treated high-input agricultural fields grown in monoculture and with fertilizers use, hence with low natural landscape diversity. Total bacterial community assessment by DNA sequencing was performed using the Illumina MiSeq platform. In total, 365 bacterial genera were identified and 6 endosymbiont taxa. A high abundance of the primary endosymbiont Buchnera and secondary symbionts Serratia and Wolbachia were detected in all maize crops. Their frequency was found to be correlated with the maize management system used, probably with fertilizer input. Three other facultative endosymbionts ("Candidatus Hamiltonella", an uncultured Rickettsiales genus, and Spiroplasma) were also recorded at different frequencies under the two management regimes. Principal components analyses revealed that the relative contribution of the obligate and dominant symbiont Buchnera to the aphid endosymbiotic bacterial community was 72%, whereas for the managed system this was only 16.3%. When facultative symbionts alone were considered, the effect of management system revealed a DNA diversity of 23.3%. [ABSTRACT FROM AUTHOR]

The rice-root aphid, Rhopalosiphum rufiabdominale (Sasaki) (Hemiptera: Aphididae) is a polyphagous species with a worldwide distribution. In June 2020, colonies of Rhopalosiphum rufiabdominale were observed on the roots of wheat in the region of Pernik, the village of Batanovci, Bulgaria. The damage is caused by the nymphs and the adults while sucking plant sap from the roots and producing honeydew. The damaged plants have a yellowish colour, retarded growth and aphid colonies present on the roots. High densities cause wilting of the whole plant and result in its death. This is the first record of the presence of Rhopalosiphum rufiabdominale on wheat roots in Bulgaria. [ABSTRACT FROM AUTHOR]

The most commercialized Bt maize plants in Europe were transformed with genes which express a truncated form of the insecticidal delta-endotoxin (Cry1Ab) from the soil bacterium Bacillus thuringiensis (Bt) specifically against Lepidoptera. Studies on the effect of transgenic maize on non-target arthropods have mainly converged on beneficial insects. However, considering the worldwide extensive cultivation of Bt maize, an increased availability of information on their possible impact on non-target pests is also required. In this study, the impact of Bt-maize on the non-target corn leaf aphid, Rhopalosiphum maidis, was examined by comparing biological traits and demographic parameters of two generations of aphids reared on transgenic maize with those on untransformed near-isogenic plants. Furthermore, free and bound phenolics content on transgenic and near-isogenic plants were measured. Here we show an increased performance of the second generation of R. maidis on Bt-maize that could be attributable to indirect effects, such as the reduction of defense against pests due to unintended changes in plant characteristics caused by the insertion of the transgene. Indeed, the comparison of Bt-maize with its corresponding near-isogenic line strongly suggests that the transformation could have induced adverse effects on the biosynthesis and accumulation of free phenolic compounds. In conclusion, even though there is adequate evidence that aphids performed better on Bt-maize than on non-Bt plants, aphid economic damage has not been reported in commercial Bt corn fields in comparison to non-Bt corn fields. Nevertheless, Bt-maize plants can be more easily exploited by R. maidis, possibly due to a lower level of secondary metabolites present in their leaves. The recognition of this mechanism increases our knowledge concerning how insect-resistant genetically modified plants impact on non-target arthropods communities, including tritrophic web interactions, and can help support a sustainable use of genetically modified crops. [ABSTRACT FROM AUTHOR]

Introduction: Keeping populations of predatory insects in the agroecosystem by offering them prey, as well as food resources from plants, is important for enhancing conservation biological control. Objective: To determine if the consumption of prey and floral food resources enhances the biological attributes of the predator Hippodamia convergens. Methods: We fed the beetle larvae two species of aphids; and the adults were fed aphids, maize tassels, and two non-cultivated plant species. We checked gut sugar in the predator by the cold anthrone test and pollen presence by the acetolysis method. Demographic experiments were done in the first 40 days after female emergence, under controlled conditions (25 °C ± 0.5; 75 % ± 1.75 Relative Humidity; Light 12 h: Darkness 12 h). Results: H. convergens did not consume fructose, but only pollen from Sorghum halepense, Parthenium hysterophorus or Zea mays. Developmental time (egg-adult) of the predator was shorter (21.4 days) when it consumed Rhopalosiphum maidis than Uroleucon nigrotibium (24.6 days); survival (L1-adult) and sex ratio did not change. Average fecundity was higher (55.5 eggs / 40 days) when consuming U. nigrotibium with pollen from P. hysterophorus, than U. nigrotibium (22.5 eggs / 40 days) or R. maidis with pollen from Zea mays (11 eggs / 40 days). The intrinsic rate of natural growth was higher when consuming U. nigrotibium with pollen from P. hysterophorus (0.055), than U. nigrotibium (0.034) or R. maidis with pollen from Z. mays (0.019). Predation rate (L1-L5) was higher when consuming R. maidis (0.65) than U. nigrotibium (0.51). Conclusions: Aphid prey species and its combination with pollen from maize and non-cultivated plants affected development time, reproduction, and predation rate of H. convergens. [ABSTRACT FROM AUTHOR]

In this study, a preliminary study was made to test the effect of host plant (maize, Zea mays) management on corn leaf aphid endosymbiotic bacterial diversity. A series of field assessments were run by collecting natural populations of corn leaf aphids from both traditionally managed (low-input) fields grown under high agricultural and natural landscape diversity and high-input agricultural fields with fertilizers, grown in monoculture under low natural landscape diversity. Bacterial total DNA sequencing was performed on an Illumina MiSeq platform. A total of 259,878 high-quality bacterial 16S rRNA gene sequences were obtained from the samples. In total, 213 bacterial genera were identified. A high abundance of primary symbionts (Buchnera sp.) and secondary symbionts (uncultured members of the family Enterobacteriaceae) were detected in all aphid samples. Other bacterial genera (Bacillus, Pseudomonas, Salipaludibacillus, Pantoea, Sphingomonas, and uncultured members of "Candidatus Moranbacteria" and "Candidatus, Falkowbacteria") were recorded, mostly from aphids collected from conventionally managed (high input) fields. The overall effect of high input treatment was such that 28% of the corn leaf aphid bacterial community distribution was affected. In contrast, low bacterial diversity was observed in corn leaf aphid populations from traditionally managed (low input) fields. These findings reveal the role of external environmental factors in governing the endosymbiotic bacterial community of aphids. [ABSTRACT FROM AUTHOR]

The polerovirus (family Solemoviridae , genus Polerovirus) genome consists of single-, positive-strand RNA organized in overlapping open reading frames (ORFs) that, in addition to others, code for protein 0 (P0, a gene silencing suppressor), a coat protein (CP, ORF3), and a read-through domain (ORF5) that is fused to the CP to form a CP-read-through (RT) protein. The genus Polerovirus contains twenty-six virus species that infect a wide variety of plants from cereals to cucurbits, to peppers. Poleroviruses are transmitted by a wide range of aphid species in the genera Rhopalosiphum, Stiobion, Aphis , and Myzus. Aphid transmission is mediated both by the CP and by the CP-RT. In viruses, mutational robustness and structural flexibility are necessary for maintaining functionality in genetically diverse sets of host plants and vectors. Under this scenario, within a virus genome, mutations preferentially accumulate in areas that are determinants of host adaptation or vector transmission. In this study, we profiled genomic variation in poleroviruses. Consistent with their multifunctional nature, single-nucleotide variation and selection analyses showed that ORFs coding for P0 and the read-through domain within the CP-RT are the most variable and contain the highest frequency of sites under positive selection. An order/disorder analysis showed that protein P0 is not disordered. In contrast, proteins CP-RT and virus protein genome-linked (VPg) contain areas of disorder. Disorder is a property of multifunctional proteins with multiple interaction partners. The results described here suggest that using contrasting mechanisms, P0, VPg, and CP-RT mediate adaptation to host plants and to vectors and are contributors to the broad host and vector range of poleroviruses. Profiling genetic variation across the polerovirus genome has practical applications in diagnostics, breeding for resistance, and identification of susceptibility genes and contributes to our understanding of virus interactions with their host, vectors, and environment. [ABSTRACT FROM AUTHOR]

Use of genetically engineered plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) have been proven efficacious for managing lepidopteran pests. However, in some cases herbivores that are not targeted by the Bt trait have increased in importance. It has been suggested that reduced caterpillar damage to Bt crops could lead to decreased levels of induced plant defensive compounds which might benefit other non‐target herbivores. Here we investigated the potential effect of reduced damage by larvae of Mythimna separata on aphid populations in Bt corn. We compared the performance of Rhopalosiphum maidis feeding on non‐Bt corn plants that had been infested by M. separata larvae or were uninfested. The results showed that caterpillar‐infested corn plants significantly reduced the fitness of R. maidis leading to a prolonged nymphal development time, reduced adult longevity and fecundity compared to uninfested plants. Consequently, the population growth rate of corn aphids feeding on caterpillar‐infested corn plants was significantly lower than on uninfested plants. As expected, the aphids performed significantly better on Lepidoptera‐resistant Bt corn than on non‐Bt corn when plants were infested with M. separata, since the caterpillars caused very little damage to the Bt plants. The current findings indicate that reduced M. separata infestation could benefit aphid development in Bt corn. Bt corn has the potential to be commercialized in China in the near future and aphids and other non‐target pests should be monitored in the farming fields. [ABSTRACT FROM AUTHOR]

Field and laboratory studies were carried out during two successive summer seasons in order to study the susceptibility of the different tested Maize cultivars namely (Giza (2), Single cross (10), and Treble cross (321) to infestation by Rhopalosphum maidis and Rhopalosiphum padi. Field studies were carried out during the two consecutive growing seasons (2016 and 2017). There were significant differences in the susceptibility of Maize cultivars to infestation by these pests. Results showed that, G 2 and S.C (10) cultivars were the lowest infested ones by the two pests. On the other hand, T.C (321) variety was the highest infested cultivar. To give a spot light on the reason of the differences in the susceptibility of the tested Maize cultivars, chemical analysis of the dried leaves were carried out during growing season of 2017. Chemical analysis of infested leaves showed correlation between certain phytochemical components; potassium, total protein, carbohydrate, and phosphorous as well as Fiber, Vt B 6 and Vt B 1 content and population density of Rhopalosphum maidis and Rhopalosiphum padi. [ABSTRACT FROM AUTHOR]

1. Climate change is expected to increase the frequency and duration of extreme heat events, which would pose significant challenges to most ectotherm species, such as insects. 2. In the study, we address the thermal tolerance of corn leaf aphid, Rhopalosiphummaidis (Hemiptera: Aphididae) under brief extreme high‐temperature events (i.e. heat waves) across life stages. Immature instars and adults of R. maidis were exposed to heat events of increasing temperatures (0.5 °C min−1), starting at 22 °C and reaching one of the selected maximal temperatures (from 38.5 to 44.5 °C with an increased interval of 0.5 °C). In each temperature regime, the mortality of R. maidis was compared with and without barley seedlings. 3. Results showed that the critical high temperature (CHT) of R. maidis was 39.0 °C in no feeding treatments, while it was 39.5 °C in feeding treatments. The upper lethal temperatures (ULTs) of R. maidis were significantly different between feeding and no feeding treatments. In addition, the ULTs varied significantly across life stages with the highest ULT values for 4th instars. Feeding significantly increased the thermal tolerance of phytophagous insects. 4. Variable balances in plant‐herbivore interactions will be induced according to the insect feeding diet status and instar stage when experiencing extreme temperatures resulting from the warming climate. The findings will provide valuable information for understanding the role of food intake in thermal adaptation of small arthropods to extreme high‐temperature events under climate change. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Plant Protection & Pathology is the property of Egyptian National Agricultural Library (ENAL) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Investigación Agraria is the property of Investigacion Agraria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize lethal necrosis disease (MLND) has emerged as a major threat to maize production in East Africa. The disease is caused by a co-infection of maize by maize chlorotic mottle virus (MCMV) and sugarcane mosaic virus (SCMV) which are respectively vectored by corn thrips, Frakliniella williamsi Hood and corn leaf aphids, Rhopalosiphum maidis Fitch. Developing a reliable and practical sampling plan and action threshold for population monitoring of the two vectors is key for implementing a reliable integrated vector management strategy. A study was carried out to determine the sampling regime and action threshold levels for the vectors. Three maize stratas (upper, mid and lower foliage levels), three sampling intervals and five spray regimes using Thunder OD 145 (110 g/L Imidacloprid and 100 g/ L Betacyfluthrin 45 g/L) (were tested. The upper plant strata proved a preferred target for corn thrips (P < 0.001) while the lower section was preferred by corn leaf aphids during season 2(P = 0.03). Scouting at 8.30 to 10.30 am (P = 0.04) gave a better estimation of the vector infestation. Corn thrips infestation was significantly lower on maize sprayed on a weekly regime (P = 0.01). However, maize crop from thunder sprayed plots was MLND negative while the unsprayed maize crop was positive (P < 0.001). Although the yield from weekly sprayed plots was higher than any other treatments (P < 0.001), the net returns from monthly sprayed plots was higher. The action threshold level for corn thrips and corn leaf aphids was found to be six and three per plant respectively. These findings provide information on how, when and where to scout and spray for the two vectors. This may eventually lead to minimal wide spread of the virus by the vectors. [ABSTRACT FROM AUTHOR]

12-Oxo-phytodienoic acid (OPDA), an intermediate in the jasmonic acid (JA) biosynthesis pathway, regulates diverse signaling functions in plants, including enhanced resistance to insect pests. We previously demonstrated that OPDA promoted enhanced callose accumulation and heightened resistance to corn leaf aphid (CLA; Rhopalosiphum maidis), a phloem sap-sucking insect pest of maize (Zea mays). In this study, we used the electrical penetration graph (EPG) technique to monitor and quantify the different CLA feeding patterns on the maize JA-deficient 12-oxo-phytodienoic acid reductase (opr7opr8) plants. CLA feeding behavior was unaffected on B73, opr7opr8 control plants (- OPDA), and opr7opr8 plants that were pretreated with OPDA (+ OPDA). However, exogenous application of OPDA on opr7opr8 plants prolonged aphid salivation, a hallmark of aphids' ability to suppress the plant defense responses. Collectively, our results indicate that CLA utilizes its salivary secretions to suppress or unplug the OPDA-mediated sieve element occlusions in maize. [ABSTRACT FROM AUTHOR]

The role of herbivores in driving the structure of freshwater macrophyte communities remains poorly understood in comparison with terrestrial ecosystems. For instance, although duckweed (subfamily Lemnoideae) are globally distributed, can be locally highly abundant and ecologically dominant, and are of growing economic importance, their interactions with herbivores remain understudied.To address how herbivores may impact duckweed species composition, we here experimentally quantify the preference and performance of a common duckweed herbivore, the water‐lily aphid (Rhopalosiphum nymphaeae) on four widespread duckweed species.Our two‐way choice experiments reveal that aphids display a preference for Spirodela polyrhiza > Landoltia punctata = Lemna minor > > Wolffia brasiliensis. These results are rarely influenced by natal host species.By evaluating the growth of aphid populations on each duckweed species, we find that preference may be adaptive in certain ecological conditions.Quantifying the population growth rate of duckweed growing in the presence and absence of aphids revealed differential tolerance of herbivory across duckweed species.This study shows that aphids, through preferential feeding and significant differential effects on duckweed growth, can have a significant impact on duckweed population dynamics and potentially community composition. [ABSTRACT FROM AUTHOR]

The use of chemicals against crop pests is more popular, in the world, than organic alternatives. These pesticides have shown harmful effects on humans and their environment. The present study aims to contribute in the creation of a biological control method against the cereal aphid Rhopalosiphum maidis by the application of extracted essential oils from rosemary (Rosmarinus officinalis) collected from three regions in Algeria (Tebessa, Constantine and El Wadi). In order to test the insecticidal potential of this plant against the adults of this pest, three concentrations (50ųl, 100ųl and 200ųl) were tested. The results reveal that R. officinalis has a very important effect on the individuals of R. maidis because the mortality, which increases with time and concentration, reached 100% with the 3rd dose after only five days. Besides, the samples from Tebessa seem more efficient than those from other localities because this rate was recorded after only three days. [ABSTRACT FROM AUTHOR]

The gene sequence encoding the mannose-binding homodimeric protein Allium sativum leaf agglutinin (ASAL) was introduced into maize inbred lines to achieve resistance against sap-sucking corn leaf aphids in transgenic lines. Maize transformants were generated after the co-cultivation of immature maize embryos with the Agrobacterium strain LB4404 harbouring a recombinant Ti-binary ASAL construct driven by the polyubiquitin promoter. The preliminary screening of maize transformants was performed via GUS histochemical analysis, and PCR and Southern blotting confirmed the insertion of the transgene and its stable integration in five transgenic maize lines. Transcript abundance was quantified by a quantitative real-time PCR assay, which revealed variable expression of the ASAL transgene among five transgenic maize lines. The highest mRNA expression of the ASAL gene was found in the A23 transgenic maize line, while the lowest expression was found in the AU1 transgenic maize line. In planta bioassays in the T1 progeny of the transgenic maize lines revealed high resistance against corn leaf aphids compared to the control non-transgenic line. The mortality of the infesting aphids (Rhopalosiphum maidi) was found to vary from 40 to 71% compared to that of the non-transgenic control maize line. [ABSTRACT FROM AUTHOR]

The species complex and infestations of aphids on plum (Prunus persica) and cherry plum (Prunus cerasifera) in Bulgaria were investigated during the period 2013–2018. Nine species from the family Aphididae were found: Brachycaudus helichrysi Kaltenbach (leaf-curling plum aphid), Hyalopterus pruni Geoffroy (mealy plum aphid), Phorodon humuli Schrank (hop aphid), Brachycaudus prunicola Kaltenbach (brown plum aphid), Brachycaudus cardui Linnaeus (thistle aphid), Brachycaudus persicae Passerini (black peach aphid), Rhopalosiphum nymphaeae Linnaeus (waterlily aphid), Aphis spiraecola Patch (spiraea aphid) and Pterochloroides persicae Cholodkovsky (peach trunk aphid). The dominant species on plum are Hyalopterus pruni and Brachycaudus helichrysi. The first species is more widespread and of significantly higher density. The dominant species on cherry plum are Phorodon humuli and B. helichrysi. The species Brachycaudus prunicola is widespread both on plum and cherry plum in Bulgaria. It was found only on twigs, and therefore cannot be considered as a dangerous pest on fruit-bearing plum trees. The other species, some of them described as dangerous pests on plum, are today fairly rare and occur in low density, thus posing no danger to orchards. [ABSTRACT FROM AUTHOR]