Dynamics Of Aphids Research Articles

Incidence, transmission, host range and population dynamics of aphids transmitting bean common mosaic virus of cowpea

Cowpea [Vigna unguiculata (Linn.) Wilczek] is an important pulse crop which belongs to family Fabaceae. Bean Common Mosaic is a major viral disease in cowpea resulting in significant yield losses to a tune of 70 per cent. The results showed that disease was widespread in all the surveyed areas, with the highest average per cent disease incidence being observed in Bagalkote (29.82%) followed by Vijayapur (27.41%), Dharwad (25.47%) and Belagavi district (18.89%). The disease incidence varied from 3.25 per cent to 69.56 per cent among the villages and from 12.94 per cent to 44.80 per cent among the taluks. The host range and transmission studies revealed that BCMV infecting cowpea is readily transmissible by sap, aphids and through seeds. The mechanical transmission was 71.43 per cent, aphid transmission was found to an extent of 54.42 per cent and the seed transmission of BCMV infecting cowpea was 64.00 per cent. The population of aphid (Aphis craccivora) was maximum during the 38th and 39th Standard Meteorological Weeks (SMWs) with the mean value of 92.70 and 81.20, respectively. The aphid population varied at different crop stages. Aphid population build up showed a strong significant negative correlation with rainfall. There was a significant negative correlation with minimum temperature and morning RH.

Population Dynamics of Aphid Pests of Wheat and Their Natural Enemies

Four aphid species (Schizaphis graminum, Sitobion avenae, Rhopalosiphum padi and Diuraphis noxia) were observed when the population dynamics of aphids in four wheat varieties were analysed. Maximum population abundance (104± 1.79 aphids/ plant) was observed during middle of March. Rhopalosiphum padi and D. noxia were predominant throughout (52.86.1± 0.21 and 56.10± 0.24 aphids/ plant, respectively). The variety ANAJ-2017 showed the least incidence (26.28± 0.27 aphids/ plant) being more resistant. Aphid parasitism was also more in ANAJ-2017 with the parasites Aphidius ervi (15.35± 0.13) and Praon volucre (12.45± 0.12). Abundance of predators (ladybird beetle, green lace wing, syrphid fly and spiders) was observed with the highly infested varieties UJALA-2016 and FSD-2008. With incidence of aphids, temperature showed positive correlation while relative humidity (RH) and rainfall did not show any significant effect. The yield varied significantly among the tested varieties and it was found positively correlated with aphid incidence with ANAJ-2017 exhibiting the maximum 1000 grain weight (55 g).

АКТИВНОСТЬ ТЛЕЙ-ПЕРЕНОСЧИКОВ ВИРУСОВ КАРТОФЕЛЯ В АРХАНГЕЛЬСКОЙ ОБЛАСТИ

The research was carried out to study the activity of aphids that carry viruses on potato plantings in the southern part of Arkhangelsk region, to assess the degree of their prevalence and the need to apply plant protection measures. The work was carried out in 2018-2022. The catching of winged forms of aphids in potato plantings was carried out using yellow water traps. In total, over a five-year period, 834 aphids were caught visiting potato plantings, which belonged to 30 different species. The most effective carriers of potato viruses are 7 of them - Acyrthosiphum pisum Harr., Aphis fabae Scop., Aphis nasturtii Kalt., Aulacorthum solani Kalt., Hyperomyzus lactucae L., Macrosiphum euphorbiae Thomas and Rhopalosiphum padi L. These species were present on plantings annually (with the exception of M. euphorbiae Thomas), and their numbers varied from 82 (in 2020) to 181 (in 2021) individuals. At the same time, the share of aphids that carry viruses in their total number ranged from 56% (in 2022) to 82% (in 2018). Over the entire period of research, not a single individual of the aphid species Myzus persicae Sulz, the most harmful to potato plantings, was identified. The prevalence of virus-carrying aphids was insignificant; there were from 21 to 46 winged insects per 1 water trap during the growing season in different years. Aphids capable of transmitting potato viruses were present on the plantings throughout the entire growing season, which indicates the need for preventive and exterminatory measures to protect plants, based on systematic annual monitoring, which makes it possible to monitor changes in the species composition, numbers and flight dynamics of aphids.

The contribution of aphids (Aphidoidea) to atmospheric concentrations of Alternaria and Cladosporium spores

Honeydew extracted by aphids serves as nutrient for the development of sooty moulds. Hypothetically, population dynamics of aphids should therefore have an effect on the airborne levels of the spores of fungi colonizing honeydew. In this study, the effects of seven aphid taxa on Alternaria and Cladosporium spore seasons (both pathogenic and allergenic fungi) were analysed on a total of 20-year-long dataset in Kecskemét (Hungary), Leicester (UK) and Poznań (Poland). Meteorological factors strongly effected both aphid and fungal populations. In most cases, a direct effect of weather on fungal levels were found. Direct effect of two aphid species, Acyrthosiphon pisum and Euceraphis punctipennis, on the atmospheric concentration of Alternaria spores was identified in Leicester and Poznań in June and July respectively. Other aphid species had secondary, but significant effects during other time periods. This suggests aphid population data can be informative in predicting airborne concentrations of Alternaria and Cladosporium spores.Graphical abstract

The Spatiotemporal Distribution, Abundance, and Seasonal Dynamics of Cotton-Infesting Aphids in the Southern U.S.

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.

Modeling the effects of plant resistance, herbivore virulence, and parasitism, on the population dynamics of aphids and parasitoids in wheat and soybean in different climates

Invasions by insects that become pests are an increasing problem for agriculture. Introductions of parasitoids from the regions of pest origin and breeding plants resistant to invasive pests can reduce the abundances and impacts of pests, while providing safe, sustainable alternatives to insecticides. However, impacts of parasitoids and plant resistance are likely to interact, and the abiotic environment, and in particular, climate change is likely to affect these interactions. Here I report results from simulations with mathematical models of population dynamics of aphids and parasitoids on resistant versus susceptible plants, parameterized with published results, designed to test the following hypotheses: (1) parasitoids can reduce abundances and frequencies of virulent aphids able to overcome plant resistance, (2) temperature regime affects the impacts of parasitoids on virulent aphids, and (3) the outcomes of these interactions vary with crop. Two systems were modeled: the soybean aphid, Aphis glycines, on soybean, and the Russian wheat aphid, Diuraphis noxia, on wheat. The parasitoids in the models are in the genus Aphelinus, species of which have a long association with biological control of invasive pests. In the simulations with these models, parasitoids reduced the abundances, and on wheat, the percent of virulent aphids. The impacts of parasitoids on virulent aphids were greater in southern locations than in northern locations, and the impacts on virulent aphids were greater on wheat than on soybean. Indeed, parasitoids actually increased the frequencies of virulent aphids on soybean when only susceptible plants were present, while reducing the abundance of all aphids. If one accepts that comparisons of population dynamics in southern versus northern locations indicate the likely affects of climate change in the northern locations, these results suggest that climate change would lead to decreased abundance and frequency of virulent aphids in northern locations.

Habitat Modification Alters Food Web Interactions with Focus on Biological Control of Aphids in Apple Orchards

To date, direct interactions between pests and natural enemies are often considered in biocontrol programs. Recently there has been an increase of evidence for the importance of third-party mediated indirect interactions in determining the population dynamics of insects. Predicting the strength of such interactions remains a central challenge in biocontrol assessments. Here, two field experiments were performed in two years to investigate to which extent Dysaphis plantaginea Passerini, Aphis pomi De Geer, and Myzus cerasi Fabricius might indirectly interact through shared natural enemies and ants. We first studied the population dynamics of target insects in isolated orchards of apples and cherries. Secondly, we investigated how the spatial coexistence of aphid-infested cherries can indirectly affect the population dynamics of apple aphids via natural enemies and ants. In the first experiment, nine parasitoid species were recorded on apple and cherry aphids, among them were three species in common. Six predatory families were found on cherry and apple aphids, while only one ant species, Lasius niger L., was found associating with these aphids. In the second experiment, temporal variation in the natural enemy-mediated apparent competition between M. cerasi and apple aphids was found. The cherry aphid is likely to be an important source of natural enemies that attack apple aphids early in the season. Significantly reduced numbers of ants associating with apple aphids in the intercropping habitat were found. Our results emphasize the importance of considering indirect interactions in the designing of pest management strategies.

INCIDENCE OF APHID BORNE VIRUSES AND THEIR VECTOR DYNAMICS INFECTING POTATO CROP IN DIFFERENT DISTRICTS OF AZAD JAMMU AND KASHMIR, PAKISTAN

Potato crop production is hampered by several fungal, viral, and bacterial diseases. Among the viral Potato leaf roll virus (PLRV), Potato virus Y (PVY), Potato-mop-top-virus (PMTV), Potato virus S (PVS) and Potato virus X (PVX) are the most important. Potato growing fields were surveyed during 2016 and 2017 to determine the incidence of two aphid-borne viruses, PVY and PLRV and to explore the dynamics of potato aphids in four potato-producing district of Azad Jammu & Kashmir (AJK), Pakistan. During survey 930 leaf samples were collected from various locations of Bagh, Sudhnoti, Poonch and Neelum. Parameters determined included aphid population, symptomology, DAC-ELISA based virus incidence, rate of co-infection and disease severity. Overall relative disease incidence of PLRV and PVY was 48.71% and 53.23% respectively. The highest average aphid’s population per field was 390.27 in Sudhnoti due to the low altitude of the surveyed locations. Three aphid species Myzuspersicae Myzusornatusand, Macrosiphum euphorbiaewere identified in AJK potato fields. Themaximum co-infection was recorded from Poonch. It was found that aphid populations decreased with the increase of altitude. The incidence of PLRV and PVY were high where aphid population was high. Therefore, it is necessary to promote awareness among the farmers on virus and aphid symptoms identification and to recommend use of healthy, uncontaminated certified potato seed.

Towards Predictions of Interaction Dynamics between Cereal Aphids and Their Natural Enemies: A Review.

Simple SummaryUnderstanding how pests and their natural enemies interact dynamically during the growing season and what drivers act on those interactions will help to develop efficient pest control strategies. We reviewed empirical and modeling publications on the drivers influencing the aphids–natural enemy dynamics. We found disparities between what is known empirically and what is used as main drivers in the models. Predation and parasitism are rarely measured empirically but are often represented in models, while plant phenology is supposed to be a strong driver of aphids’ dynamics while it is rarely used in models. Since modelers and empirical scientists do not share a lot of publications, we incite more crossover works between both communities to elaborate (i) new empirical settings based on simulation results and (ii) build more accurate and robust models integrating more key drivers of the aphid dynamics. These models could be integrated into decision support systems to help advisors and farmers to design more effective integrated pest management systems.(1) Although most past studies are based on static analyses of the pest regulation drivers, evidence shows that a greater focus on the temporal dynamics of these interactions is urgently required to develop more efficient strategies. (2) Focusing on aphids, we systematically reviewed (i) empirical knowledge on the drivers influencing the dynamics of aphid–natural enemy interactions and (ii) models developed to simulate temporal or spatio-temporal aphid dynamics. (3) Reviewed studies mainly focus on the abundance dynamics of aphids and their natural enemies, and on aphid population growth rates. The dynamics of parasitism and predation are rarely measured empirically, although it is often represented in models. Temperature is mostly positively correlated with aphid population growth rates. Plant phenology and landscape effects are poorly represented in models. (4) We propose a research agenda to progress towards models and empirical knowledge usable to design effective CBC strategies. We claim that crossover works between empirical and modeling community will help design new empirical settings based on simulation results and build more accurate and robust models integrating more key drivers of aphid dynamics. Such models, turned into decision support systems, are urgently needed by farmers and advisors in order to design effective integrated pest management.

Population dynamics of aphids and its predators alongwith its management

In Pakistan, oilseed cultivations belonging to Brassica genus (Rapeseed, Mustard and Canola) are the most essential crops with respect to eatable oil production. In Indo-Pak, such cultivations have considered as chief oil origins over centuries. This trail was executed at the Ghazi University, D. G. Khan, and Air-Port Campus farming area. The outcomes revealed that insecticidal based treatments significantly reduced the aphid population by the application Bifenthrin and Acetamaprid. In case of botanical extracts, Allium cepa and Moringa oleifera induced mortality of aphid. Moreover, insecticide based treatments reduced percent predator population increasingly than botanical extracts.

Survey and population dynamics of cereal aphids and their common natural enemies inhabiting wheat crop in Hail region, Saudi Arabia

AbstractCereal aphids are known as serious pests that cause considerable yield losses of wheat production. In this study, cereal aphids and their common natural enemies inhabiting the commercial wheat crop were investigated between February and April 2013 as a preliminary study in the Hail region, northern Saudi Arabia. Results showed that wheat crops were infested by four aphid species including the Russian wheat aphid Diuraphis noxia Kurdjumov, the English grain aphid Sitobion avenae Fabricius, the bird cherry‐oat aphid Rhopalosiphum padi L. and the greenbug aphid Schizaphis graminum Rondani (Homoptera: Aphididae). The Russian wheat aphid D. noxia, however, was the most abundant species compared to other aphid species, totaling 343 individuals which represented 39.80% of all cereal aphids. The results showed a diverse community of specialist natural enemies that were associated aphids including parasitoid wasps as a complex and one Braconid species Aphidius matricariae Haliday (Hymenoptera: Braconidae), three coccinellid species (Adonia variegate Goeze, Coccinella quinquepunctata L. and Coccinella septimpunctata L.) (Coleoptera: Coccinellidae), one species of lacewing Chrysopa sp. (adults & larvae) (Neuroptera: Chrysopidae) and one species of hoverfly Eristalinus aeneus Scop. (adults and larvae) (Diptera: Syrphidae). This study, also, recorded a high abundance of polyphagous predators that included two species of ground beetles involving the black beetle Calosoma olivieri Dejean and Calosoma imbricatum Klug (Coleoptera: Carabidae), and spiders (Araneae) as generalist natural enemies of cereal aphids. In this article, population dynamics of captured cereal aphids and their common natural enemies, and their correlations will be described and discussed.

Population dynamics of aphid and coexisting predators in tomato agroecosystem


 Aphids generally attack vegetative plant parts, preferably leaves, and devitalize the plant by sucking the cell sap. Thorough knowledge of pest-predator ecology and their interaction is requisite to initiate timely pest management strategies. Therefore, we aimed to study the population dynamics of aphids and their predators on tomato in Hisar, Haryana during Rabi, 2016-17 and 2017-18. We observed two dominant aphid species viz., Aphis gossypii and Myzus persicae and three aphidophagous predator groups viz., coccinellids, spiders and syrphid fly maggots in the tomato agroecosystem. Aphid infestation started during the 9th standard meteorological week (SMW) and attained a peak during the 12th SMW (22.65 aphids per three leaves per plant). Aphid population exhibited highly significant negative correlation with minimum temperature (r= -0.917**), maximum temperature (r= -0.895**) and wind speed (r= -0.809**). However, it was positively correlated with morning relative humidity (r= 0.933**) and evening relative humidity (r= 0.856**). We used Principal component analysis (PCA) to reduce the dimensions of data and variables were transformed into principal components (PC) to explain the nature and extent of the relationships among different variables. PC1 and PC2 capture 57.6 and 20.3% of the variability in the data, respectively. Aphid predators exhibited a significant positive correlation with the prey population suggesting a positive density-dependent response.

Seasonal dynamics of bean aphids and its relationship with the abundance of Lady Bird Beetles

The seasonal dynamics of aphid Aphis craccivora Koch (Hemiptera: Aphididae) on four bean species namely country bean Lablab purpureus, yard long bean Vigna sesquipedalis, hyacinth bean Dolichos lablab and bush bean Phaseolus vulgaris were studied from September to December 2017 in the experimental field of the Department of Entomology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh. The study also investigated the relationship between the abundance of aphid and its predatory insect lady bird beetle. Aphid abundance on the bean species showed increasing trend from the 4th week of September and reached to the peak during the 2nd week of November and then declined. Bush bean and yard long bean, respectively depicted the higher and lower abundances of aphid throughout the study. Relationship between the abundance of aphid and lady bird beetle on the bean species were positively correlated. Aphid showed negatively correlation with temperature and rainfall, and positive correlation with relative humidity, and the correlations were not significant. Multiple regression equation showed that temperature had the highest effect which contributed 16.1 - 19.2% role on the population of aphid.
 Bangladesh J. Zool. 48(2): 357-363, 2020

Population dynamics and species composition of maize field parasitoids attacking aphids in northeastern China

Maize, Zea mays L., is the most abundant field crop in China. Aphids are the most economically damaging pest on maize, particularly in the maize agri-ecosystems of Jilin Province, northeastern China. Parasitic wasps are important natural enemies of aphids, but limited information exists about their species composition, richness and seasonal dynamics in northeastern China. In this study, the population dynamics of maize aphids and parasitoid wasps were assessed in relation to each other during the summer seasons of two consecutive years, 2018 and 2019. We selected maize fields in the Changchun, Songyuan, Huinan and Gongzhuling areas of Jilin Province. Four species of aphids were recorded from these maize fields: Rhopalosiphum padi (L), Rhopalosiphum maidis (Fitch), Aphis gossypii Glover and Macrosiphum miscanthi (Takahashi). The dominant species in each of the four areas were R. maids (Filch) and R. padi in Changchun, R. padi in Songyuan, A. gossypii and R. padi in Huinan, and A.gossypii and R. padi in Gongzhuling. We delineated a species complex made up of primary parasitoids and hyperparasitoids associated with maize aphids. The primary parasitoids Lysiphlebus testaceipes, Binodoxys communis and Aphelinus albipodus together formed approximately 85.3% of the parasitoid complex. Pachyneuron aphidis, Phaenoglyphis villosa, Syrphophagus taeniatus and Asaphes suspensus made up the hyperparasitoids. Of the primary parasitoids, L. testaceipes was the dominant species (81.31%). Of the hyperparasitoid group, P. villosa was the dominant species (68.42%). Parasitism rates followed the fluctuation of the aphid population. The highest parasitic rate was observed during the peak period of cotton aphids. In this paper, the occurrence dynamics and dominant species of aphids and the dynamics of parasitic natural enemies of aphids in maize fields in Jilin Province are, for the first time, systematically reported. This study provides important information for the establishment and promotion of aphid biological control in maize fields.

Population dynamics of winged aphids in areas of Aichi Prefecture, where the ringspot disease of Japanese apricot occurs, and the effects of emergency control measures on virus load in winged aphids

Population dynamics of winged aphids in areas of Aichi Prefecture, where the ringspot disease of Japanese apricot occurs, and the effects of emergency control measures on virus load in winged aphids

Population dynamics of wheat aphids Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) at District Mardan, Khyber Pakhtunkhwa Pakistan

Wheat (Triticum aestivum L.) is one of the major source of food worldwide. However, it suffers from numerous constraints. The aphids, particularly Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) species are among the major causes that severly affect wheat production acrossthe globe. To determine the population dynamics of aphids associated with wheat crop in Khyber Pakhtunkhwa, we examined the mean population of both species in the selected areas (Maho Dheri, Sarband, Kandare, Rag Narai and Khazana Dheri) of district Mardan in 2015. The mean population of R. padi and S. avenae per plant were recorded every week by counting the number of aphids on 5 plants picked up randomly from each selected wheat field using the diagonal methods. The results on current study showed that the infestation of both aphid species was started in the 1st week of February (05 standard weeks). The densities of aphids per plant increased as the vegetative growth proceeded and was highest till the mid of March (10th and 11th standard week). The declined in aphid populations for both species were started after mid of March and ended in April. The mean population of both aphid species was found low in the 1st week of February (05th standard week) that is probably due to the low temperature. The population density of aphids reached to the its peak in the second week of March due to suitable temperature for aphid infestation. Keywords: District Mardan; Population dynamics; Rhopalosiphum padi; Sitobion avenae and Wheat http://dx.doi.org/10.19045/bspab.2020.90004

Integrating Models of Atmospheric Dispersion and Crop-Pest Dynamics: Linking Detection of Local Aphid Infestations to Forecasts of Region-Wide Invasion of Cereal Crops

Abstract Invasive airborne insects pose major challenges in natural resource and agriculture management, as they can rapidly spread over large distances and cross physical boundaries. Field monitoring and local management are important tools to prevent and control infestations but require additional coordination to be operative region-wide. Computational modeling techniques have been effective in simulating local population dynamics and in capturing spread of invasive species on a regional scale. We use an integrated ecological model to simulate local and regional infestation dynamics of sugarcane aphids, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), on sorghum, Sorghum bicolor (L.) Moench (family Poaceae), in the southern to central Great Plains of the United States. Local dynamics of aphid populations on sorghum are simulated by a spatially explicit, individual-based model, whereas regional aphid migration is simulated by an atmospheric model that computes inert air particle (aphid) transport, dispersion, and deposition. Simulation results indicate timing of initial infestations in the south affects spatiotemporal patterns of infestation throughout the region. Probability of local infestations is a function of both percentage of land occupied by growing sorghum and prevailing winds. Thus, due to availability of sorghum, relatively later dates of initial infestation in the south will probably lead to infestations farther north that become established more quickly following the first appearance of aphids in the south. The model we present, in coordination with field monitoring schemes, could be applied as a forecasting tool in region-wide pest management systems.

The impact of ant mutualistic and antagonistic interactions on the population dynamics of sap-sucking hemipterans in pear orchards.

Ants are known to establish antagonistic and mutualistic interactions with honeydew-producing hemipterans, depending on the species involved and the ecological context. The aim of this work was to infer the role that such interactions play in the population dynamics of psyllids and aphids in pear orchards. Interactions were inferred from field data and periodical sampling along a 4-year study, and from interaction assays performed under controlled conditions. A decline in the abundance of the pear psyllid (Cacopsylla pyri L.), parallel to an increase in the abundance of aphids, was registered over 4 years. Ants were the dominant species, representing about 90% of the predators, followed by spiders and predatory hemipterans (namely Pilophorus gallicus Remane). Ant abundance increased over the 4 years, matching the population dynamics of aphids. Evidence of mutualistic and antagonistic interactions were found for ant-aphid and ant-psyllid, respectively: (i) ant-aphid abundances on pear trees were positively correlated, and ants reduced predation on aphids by generalist predators, and (ii) ant-psyllid abundances were negatively correlated, ants have a negative effect on the psyllid population growth rates, and ants were found to prey on the psyllid. Because of their high abundance in comparison with other predators and the mutualistic-antagonistic relationships with aphids-psyllids, ants are considered to be the principal force behind the decline of pear psyllid populations and the increase in aphid numbers. In summary, ants contribute positively to biological control by the suppresion of pests (i.e. the psyllid) which are more damaging than those they protect (i.e. aphids). © 2019 Society of Chemical Industry.

Characterization of Hymenopteran Parasitoids of Aphis fabae in an African Smallholder Bean Farming System through Sequencing of COI 'Mini-Barcodes'.

Parasitoids are among the most frequently reported natural enemies of insect pests, particularly aphids. The efficacy of parasitoids as biocontrol agents is influenced by biotic and abiotic factors. For example, hyperparasitoids can reduce the abundance of the primary parasitoids as well as modify their behavior. A field study was conducted at three contrasting elevations on Mount Kilimanjaro, Tanzania, to identify the parasitoids of aphids in smallholder bean farming agroecosystems. Sentinel aphids (Aphis fabae) on potted bean plants (Phaseolus vulgaris) were exposed in 15 bean fields at three elevations for 2 days. The sentinel aphids were then kept in cages in a greenhouse until emergence of the parasitoids, which were collected and preserved in 98% ethanol for identification. Of the 214 parasitoids that emerged from sentinel aphids, the greatest abundance (44.86%) were from those placed at intermediate elevations (1000–1500 m a.s.l), compared to 42.52% from the lowest elevations and only 12.62% from the highest elevation farms. Morphological identification of the parasitoids that emerged from parasitized aphids showed that 90% were Aphidius species (Hymenoptera: Braconidae: Aphidiinae). Further characterization by sequencing DNA ‘mini-barcodes’ identified parasitoids with ≥99% sequence similarity to Aphidius colemani, 94–95% sequence similarity to Pachyneuron aphidis and 90% similarity to a Charipinae sp. in the National Center for Biotechnology Information (NCBI) database. These results confidently identified A. colemani as the dominant primary aphid parasitoid of A. fabae in the study area. A Pachyneuron sp., which was most closely related to P. aphidis, and a Charipinae sp. occurred as hyperparasitoids. Thus, interventions to improve landscapes and farming practice should monitor specifically how to augment populations of A. colemani, to ensure any changes enhance the delivery of natural pest regulation. Further studies are needed for continuous monitoring of the hyperparasitism levels and the dynamics of aphids, primary parasitoids, and secondary parasitoids in different cropping seasons and their implications in aphid control.

Intraguild predation is independent of landscape context and does not affect the temporal dynamics of aphids in cereal fields

Abundance and diversity of natural enemies increases with higher landscape complexity. However, more species can also increase negative interactions such as intraguild predation (IGP), which could be detrimental to pest control. Direct observations of these trophic interactions are still lacking. In the present study, we employed DNA-based gut content analyses of coccinellid beetles to assess IGP (direct and coincidental) and aphid consumption. Species-specific and group-specific primer pairs were used to unveil the interactions of the most abundant coccinellid species, three cereal aphids and their associated parasitoids. In order to determine whether the landscape complexity promotes these interactions, we used replicated wheat fields in two contrasting landscape contexts over the season in central Chile. With higher abundance of coccinellids, we observed greater aphid consumption in complex contexts. The consumption of parasitized aphids was mostly detected early in complex contexts, suggesting a detrimental effect on the parasitoid population. Following molecular analysis, we can state that the aphids are important feeding resources for the coccinellid assemblage and are actively foraging on this important pest. Finally, this study demonstrates that direct IGP is a common interaction in this system, independently of the landscape context during the complete season. Nevertheless, the native Eriopis chilensis was found to be the most frequently consumed intraguild prey. In contrast with expected predictions, we found little evidence that the landscape context increased negative interactions, such as IGP and IGP-C and in turn that these decrease the control of Sitobion avenae.