Aphid Host Research Articles

Aphids harbouring different endosymbionts exhibit differences in cuticular hydrocarbon profiles that can be recognized by ant mutualists

Cuticular hydrocarbons (CHCs) have important communicative functions for ants, which use CHC profiles to recognize mutualistic aphid partners. Aphid endosymbionts can influence the quality of their hosts as ant mutualists, via effects on honeydew composition, and might also affect CHC profiles, suggesting that ants could potentially use CHC cues to discriminate among aphid lines harbouring different endosymbionts. We explored how several strains of Hamiltonella defensa and Regiella insecticola influence the CHC profiles of host aphids (Aphis fabae) and the ability of aphid-tending ants (Lasius niger) to distinguish the profiles of aphids hosting different endosymbionts. We found significant compositional differences between the CHCs of aphids with different infections. Some endosymbionts changed the proportions of odd-chain linear alkanes, while others changed primarily methyl-branched compounds, which may be particularly important for communication. Behavioural assays, in which we trained ants to associate CHC profiles of endosymbiont infected or uninfected aphids with food rewards, revealed that ants readily learned to distinguish differences in aphid CHC profiles associated with variation in endosymbiont strains. While previous work has documented endosymbiont effects on aphid interactions with antagonists, the current findings support the hypothesis that endosymbionts also alter traits that influence communicative interactions with ant mutualists.

Developmental Temperature Affects Life-History Traits and Heat Tolerance in the Aphid Parasitoid Aphidius colemani.

Simple SummaryIndividual insects can experience different temperatures across their lives. In consequence, development of immature stages can take place at temperatures contrasting with those that the adult will encounter. In order to study the adaptation of organisms to warm environments, it is interesting to establish the links between developmental temperature and responses of the adult generation, in terms of physiology, morphology, and behavior. We exposed the parasitoid Aphidius colemani to three temperatures during larval development (10, 20, or 28 °C). We then measured the responses of adult parasitoids regarding their traits (physiology, morphology) and their tolerance to high temperatures. Mass, lipid reserves, survival, and heat tolerance of adults were affected by the rearing temperature regime. This means that, overall, developmental temperatures may affect how insects respond to a given temperature once they are adults, which may consequently influence the ability of parasitoids to control their aphid hosts. These results are important in the context of biological control in hot environments, such as the Maghreb, where this species of parasitoid is used in mass release techniques to control aphids in various crops.Developmental temperature plays important roles in the expression of insect traits through thermal developmental plasticity. We exposed the aphid parasitoid Aphidius colemani to different temperature regimes (10, 20, or 28 °C) throughout larval development and studied the expression of morphological and physiological traits indicator of fitness and heat tolerance in the adult. We showed that the mass decreased and the surface to volume ratio of parasitoids increased with the development temperature. Water content was not affected by rearing temperature, but parasitoids accumulated more lipids when reared at 20 °C. Egg content was not affected by developmental temperature, but adult survival was better for parasitoids reared at 20 °C. Finally, parasitoids developed at 20 °C showed the highest heat stupor threshold, whereas parasitoids developed at 28 °C showed the highest heat coma threshold (better heat tolerance CTmax1 and CTmax2, respectively), therefore only partly supporting the beneficial acclimation hypothesis. From a fundamental point of view, our study highlights the role of thermal plasticity (adaptive or not) on the expression of different life history traits in insects and the possible correlations that exist between these traits. From an applied perspective, these results are important in the context of biological control through mass release techniques of parasitoids in hot environments.

Aphid parasitoid, Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae): opportunities for its use in integrated management of aphids infesting rapeseed-mustard in north-western Indian Himalayas

The aphid endoparasitoid Diaeretiella rapae (McIntosh), parasitizing green peach aphid Myzus persicae (Sulzer), mustard aphid Lipaphis erysimi (Kaltenbach) and cabbage aphid Brevicoryne brassicae (L.) in Kangra, Kullu, Mandi, Shimla, Hamirpur, Sirmaur, Una and Bilaspur districts of north Indian Himalayan state, Himachal Pradesh was studied. At different locations, parasitism by D. rapae in December, January, February and March ranged from 0.00 to 5.30, 0.00 to 16.40, 19.30 to 31.20 and 0.00 to 49.80%. Under field conditions, experiments were conducted to evaluate the side effect of some commonly used chemical insecticides and biopesticides on D. rapae. Percent parasitism by D. rapae in dimethoate treated plots was negatively affected, and it reduced from 11.85 to 0.01%, whereas biopesticides didn't affect the parasitism. Further laboratory investigations assessed the suitability of aphids viz. M. persicae, B. brassicae and L. erysimi as hosts for mass rearing of D. rapae. Among the aphid hosts, second nymphal instar of M. persicae was found to be the larger in size, followed by B. brassicae and L. erysimi. D. rapae reared on M. persicae were larger in size compared to those reared on B. brassicae and L. erysimi. Further, M. persicae reared on Capsicum annuum proved to be the best aphid host for D. rapae based on high percent parasitism (58.60%) and high fertility (76 eggs/female). The current research advises that D. rapae can be mass reared on aphid hosts in a laboratory that would supplement augmentative biological control in rapeseed-mustard. Our results also demonstrate that biopesticides can be used against aphids infesting rapeseed-mustard, with limited risk to the parasitoid, D. rapae and can be a fruitful option to chemical-based insecticides.

Geography-dependent symbiont communities in two oligophagous aphid species.

ABSTRACTAphids and their diverse symbionts have become a good model to study bacteria-arthropod symbiosis. The feeding habits of aphids are usually influenced by a variety of symbionts. Most studies on symbiont diversity have focused on polyphagous aphids, while symbiont community patterns for oligophagous aphids remain unclear. Here, we surveyed the bacterial communities in natural populations of two oligophagous aphids, Melanaphis sacchari and Neophyllaphis podocarpi, in natural populations. Seven common symbionts were detected, among which Buchnera aphidicola and Wolbachia were the most prevalent. In addition, an uncommon Sodalis-like symbiont was also detected in these two aphids, and Gilliamella was found in some samples of M. sacchari. We further assessed the significant variation in symbiont communities within the two aphid species, geographical regions and host specialization using statistical and ordination analyses. Geography was an important factor in shaping the symbiont community structure in these oligophagous aphids. Furthermore, the strong geographical influence may be related to specific environmental factors, especially temperature, among different regions. These findings extend our knowledge of the significance of geography and its associated environmental conditions in the symbiont community structure associated with oligophagous aphids.

Study of aphid parasitoids (Hymenoptera: Braconidae) in Australian grain production landscapes

AbstractAphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) were surveyed within grain production landscapes in Victoria, Australia, between 2017 and 2018, as well as more sporadically nationwide between 2016 and 2019. In addition, Aphidiinae records were collated from insect depositories around Australia and online databases. The 5525 specimens recorded constituted a total of 23 species and seven genera. Diaeretiella rapae (M'Intosh) was the most common species, representing more than 70% of all Aphidiinae recorded. This species also showed a greater northerly geographical range than other Aphidiinae. During sampling between 2017 and 2019, Aphidiinae were reared from mummies to ascertain host–parasitoid relationships. Diaeretiella rapae was again the most commonly reared parasitoid, although parasitoid preference varied with aphid host and between states and territories. An illustrated dichotomous key to Australian Aphidiinae in grain production landscapes is provided for the 11 species sampled in our field surveys. This is the first comprehensive review of Aphidiinae sampled within Australia in over two decades. Knowledge about the diversity and distribution of these parasitoids is important for understanding their impact on current and future invasions of aphid species. In addition, understanding the interactions between grain aphids and their associated parasitoids will further support the inclusion of parasitoid wasps into integrated pest management (IPM) strategies.

Distribution and structure of aphid and their parasitoids community in the Kurdistan Region-Iraq

Aphids are significant pests to many host plant species throughout the world. Aphids are on the other hand parasitized by a variety of parasitoid wasps which can potentially be used as biocontrol agents. The focus of the present study is on the pattern and distribution of the aphids and their parasitoids in the Kurdistan region in the northern part of Iraq. A field study was conducted at four locations with different bio-geographic elements and climatic conditions on several different host plant species. It turned out that the highest number of aphids and parasitoids was recorded in Darbandi Gomaspan and the lowest number of aphid and parasitoids was in Choman. Number of parasitoids were generally lower than the number of aphids. The parasitoids presented in this work have been reared from 13 aphid host taxa occurring on plants sampled from different locations. Most of the species of parasitoids belonging to the families Braconidae and Aphelinidae.  The results of this study can be considered as a first data on the population of aphids and their parasitoids in this region. Further research will be undertaken for promising the biological control of aphid pests in this region.

Drought has negative consequences on aphid fitness and plant vigor: Insights from a meta-analysis.

Aphids are abundant in natural and managed vegetation, supporting a diverse community of organisms and causing damage to agricultural crops. Due to a changing climate, periods of drought are anticipated to increase, and the potential consequences of this for aphid–plant interactions are unclear.Using a meta‐analysis and synthesis approach, we aimed to advance understanding of how increased drought incidence will affect this ecologically and economically important insect group and to characterize any potential underlying mechanisms. We used qualitative and quantitative synthesis techniques to determine whether drought stress has a negative, positive, or null effect on aphid fitness and examined these effects in relation to (a) aphid biology, (b) geographical region, and (c) host plant biology.Across all studies, aphid fitness is typically reduced under drought. Subgroup analysis detected no difference in relation to aphid biology, geographical region, or the aphid–plant combination, indicating the negative effect of drought on aphids is potentially universal. Furthermore, drought stress had a negative impact on plant vigor and increased plant concentrations of defensive chemicals, suggesting the observed response of aphids is associated with reduced plant vigor and increased chemical defense in drought‐stressed plants.We propose a conceptual model to predict drought effects on aphid fitness in relation to plant vigor and defense to stimulate further research.

Responses to predation risk cues and alarm pheromones affect plant virus transmission by an aphid vector.

Herbivores assess predation risk in their environment by identifying visual, chemical, and tactile predator cues. Detection of predator cues can induce risk-avoidance behaviors in herbivores that affect feeding, dispersal, and host selection in ways that minimize mortality and reproductive costs. For herbivores that transmit plant pathogens, including many aphids, changes in herbivore behavior in response to predator cues may also affect pathogen spread. However, few studies have assessed how aphid behavioral responses to different types of predator cues affect pathogen transmission. Here, we conducted greenhouse experiments to assess whether responses of pea aphids (Acyrthosiphon pisum) to predation risk and alarm pheromone (E-β-Farnesene), an aphid alarm signal released in response to predation risk, affected transmission of Pea enation mosaic virus (PEMV). We exposed A. pisum individuals to risk cues, and quantified viral titer in aphids and pea (Pisum sativum) host plants across several time periods. We also assessed how A. pisum responses to risk cues affected aphid nutrition, reproduction, and host selection. We show that exposure to predator cues and alarm pheromone significantly reduced PEMV acquisition and inoculation. Although vectors avoided hosts with predator cues, predator cues did not alter vector reproduction or reduce nutrient acquisition. Overall, these results suggest that non-consumptive effects of predators may indirectly decrease the spread of plant pathogens by altering vector behavior in ways that reduce vector competence and pathogen transmission efficiency.

Adaptive Variation of Buchnera Endosymbiont Density in Aphid Host Acyrthosiphon pisum Controlled by Environmental Conditions.

The scarcity of transcriptional regulatory genes in Buchnera aphidicola, an obligate endosymbiont in aphids, suggests the stability of expressed gene patterns and metabolic pathways. This observation argues in favor of the hypothesis that this endosymbiont bacteria might contribute little to the host adaptation when aphid hosts are facing challenging fluctuating environment. Finding evidence for the increased expression or silenced genes involved in metabolic pathways under the pressure of stress conditions and/or a given environment has been challenging for experimenters with this bacterial symbiotic model. Transcriptomic data have shown that Buchnera gene expression changes are confined to a narrow range when the aphids face brutal environmental variations. In this report, we demonstrate that instead of manipulating individual genes, the conditions may act on the relative mass of endosymbiont corresponding to the needs of the host. The control of the fluctuating number of endosymbiont cells per individual host appears to be an unexpected regulatory modality that contributes to the adaptation of aphids to their environment. This feature may account for the success of the symbiotic advantages in overcoming the drastic changes in temperature and food supplies during evolution.

Functional response of Harmonia axyridis preying on Acyrthosiphon pisum nymphs: the\xa0effect of temperature

In the current study, we investigated the functional response of Harmonia axyridis adults and larvae foraging on Acyrthosiphon pisum nymphs at temperatures between 15 and 35 °C. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of the functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to A. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instar H. axyridis consumed the most aphids. For fourth instar larvae and female H. axyridis adults, the successful attack rates were 0.23 ± 0.014 h−1 and 0.25 ± 0.015 h−1; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

Serratia symbiotica Enhances Fatty Acid Metabolism of Pea Aphid to Promote Host Development.

Bacterial symbionts associated with insects are often involved in host development and ecological adaptation. Serratia symbiotica, a common facultative endosymbiont harbored in pea aphids, improves host fitness and heat tolerance, but studies concerning the nutritional metabolism and impact on the aphid host associated with carrying Serratia are limited. In the current study, we showed that Serratia-infected aphids had a shorter nymphal developmental time and higher body weight than Serratia-free aphids when fed on detached leaves. Genes connecting to fatty acid biosynthesis and elongation were up-regulated in Serratia-infected aphids. Specifically, elevated expression of fatty acid synthase 1 (FASN1) and diacylglycerol-o-acyltransferase 2 (DGAT2) could result in accumulation of myristic acid, palmitic acid, linoleic acid, and arachidic acid in fat bodies. Impairing fatty acid synthesis in Serratia-infected pea aphids either by a pharmacological inhibitor or through silencing FASN1 and DGAT2 expression prolonged the nymphal growth period and decreased the aphid body weight. Conversely, supplementation of myristic acid (C14:0) to these aphids restored their normal development and weight gain. Our results indicated that Serratia promoted development and growth of its aphid host through enhancing fatty acid biosynthesis. Our discovery has shed more light on nutritional effects underlying the symbiosis between aphids and facultative endosymbionts.

Changes in Aphid-Plant Interactions under Increased Temperature.

Simple SummaryThe changing climate, particularly the temperature increase, can affect both herbivorous insects and plants. Aphids, being poikilothermal organisms, are directly exposed to an increase in temperature that, in turn, affects their biology. An increase in temperature can also indirectly affect aphids by changing the quality of the host plant tissues. This work focused on investigating the effects of climate change on plant–insect interaction. In particular, it was analyzed how an increase in ambient temperature can affect the condition of Macrosiphum rosae and its host Rosa rugosa, and how it correlates with the activity of oxidative stress-related enzymes (SOD, CAT, POD, β-glucosidase, GST, and PPO) both in insect and plant tissues. Thermal stress ranging from 25 to 28 °C has a significant impact on M. rosae–R. rugosa interaction, affecting aphid fitness and the activity of enzymes related to oxidative stress in both insect and plant.Thermal stress in living organisms causes an imbalance between the processes of creating and neutralizing reactive oxygen species (ROS). The work aims to explain changes in the aphid–host plant interaction due to an increase in temperature. Tests were carried out at three constant temperatures (20, 25, or 28 °C). Firstly, changes in development of Macrosiphum rosae were determined. Secondly, the activity of enzymatic markers (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), β-glucosidase, polyphenol oxidase (PPO), and peroxidase (POD)) in aphid M. rosae tissues and host plant were analyzed at all temperatures. An increase in temperature to 28 °C had a negative effect on the biology of M. rosae by shortening the period of reproduction and longevity, thus reducing the demographic parameters and fecundity. Two stages of the aphid’s defensive response to short-term (24–96 h) and long-term (2 weeks) thermal stress were observed. Aphid defense responses varied considerably with temperature and were highest at 28 °C. In turn, for the plants, which were exposed to both abiotic stress caused by elevated temperature and biotic stress caused by aphid feeding, their enzymatic defense was more effective at 20 °C, when enzyme activities at their highest were observed.

Characterization of the detrimental effects of type IV glandular trichomes on the aphid Macrosiphum euphorbiae in tomato

Glandular trichomes are essential in plants' defence against pests however, the mechanisms of action are not completely understood. While there is considerable evidence of feeding and movement impairment by trichomes, the effect on other traits is less clear. We combined laboratory and greenhouse experiments with molecular analysis to understand how glandular trichomes affect the behavior, population growth, and the expression of biomarkers involved in detoxification, primary metabolism, and developmental pathways of the aphid Macrosiphum euphorbiae. We used two isogenic tomato lines that differ in the presence of type IV glandular trichomes and production of acylsucroses; i.e.,Solanum lycopersicum cv. 'Moneymaker' and an introgressed line from Solanum pimpinellifolium (with trichomes type IV). Type IV glandular trichomes affected host selection and aphid proliferation with aphids avoiding, and showing impaired multiplication on the genotype with trichomes. The exposure to type IV glandular trichomes resulted in the overexpression of detoxication markers (i.e., Hsp70, Hsp17, Hsp10); the repression of the energetic metabolism (GAPDH), and the activation of the ecdysone pathway; all these, underlying the key adaptations and metabolic trade-offs in aphids exposed to glandular trichomes. Our results demonstrate the detrimental effect of glandular trichomes (type IV) on the aphid and put forward their mode of action. Given the prevalence of glandular trichomes in wild and cultivated Solanaceae; and of the investigated molecular biomarkers in insects in general, our results provide relevant mechanisms to understand the effect of trichomes not only on herbivorous insects but also on other trophic levels.

Isolation of the Buchnera aphidicola flagellum basal body complexes from the Buchnera membrane.

Buchnera aphidicola is an intracellular bacterial symbiont of aphids and maintains a small genome of only 600 kbps. Buchnera is thought to maintain only genes relevant to the symbiosis with its aphid host. Curiously, the Buchnera genome contains gene clusters coding for flagellum basal body structural proteins and for flagellum type III export machinery. These structures have been shown to be highly expressed and present in large numbers on Buchnera cells. No recognizable pathogenicity factors or secreted proteins have been identified in the Buchnera genome, and the relevance of this protein complex to the symbiosis is unknown. Here, we show isolation of Buchnera flagellum basal body proteins from the cellular membrane of Buchnera, confirming the enrichment of flagellum basal body proteins relative to other proteins in the Buchnera proteome. This will facilitate studies of the structure and function of the Buchnera flagellum structure, and its role in this model symbiosis.

Benefits and costs of hosting facultative symbionts in plant-sucking insects: A meta-analysis.

Many animals have evolved associations with symbiotic microbes that benefit the host through increased growth, lifespan, and survival. Some interactions are obligate (essential for survival) while others are facultative (usually beneficial but not essential). Not all individuals host all facultative symbionts in a population, and thus there is probably a trade-off between the cost of hosting these symbionts and the benefits they confer to the host. Plant-sucking insects have been one of the most important models to test these costs and benefits experimentally. This research is now moving beyond the description of symbiont effects towards understanding the mechanisms of action, and their role in the wider ecological community. We present a quantitative and systematic analysis of the published evidence exploring this question. We found that whitefly and true bugs experience benefits through increased growth and fecundity, whereas aphids experience costs to their fecundity but benefits through increased resistance to natural enemies. We also report the lack of data in some plant-sucking groups, and explore variation in effect strengths and directions across aphid host, symbiont and plant species thus highlighting the importance of considering the context dependency of these interactions.

Morphology of immature stages of Aphelinus maculatus Yasnosh (Hymenoptera: Aphelinidae) related to host aphid characteristics and larval taxonomic significance

The aphid parasitoid, Aphelinus maculatus Yasnosh (Hymenoptera: Aphelinidae), first described as a new record in China in 2016, is one of the most important natural enemies of the Chinese wolf-berry aphids. In order to relate its larval development stages to morphological changes of both the parasitoid and its host aphid during the parasitoid development, and to explore the larval taxonomic significance, a laboratory dissection study was conducted under the light microscope. There are three larval instars during immature development of A. maculatus. Instars differ in body shape, mandibles and numbers of respiratory spiracles. The first instar larva of A. maculatus is elongate in shape, the second instar larva is thick spindle-shaped to spindle-shaped, and the third instar larva is spherical-shaped with a small tail. Mandibles of the first and second instar larvae of A. maculatus are almost invisible, and their pharynxes are well developed. Mandibles of the third instar larva are well developed and are made of a pair of dark yellow sharp pointed spines each projecting from a transparent broad triangular base. The third instar larva possesses seven pairs of respiratory spiracles with one pair on the mesothorax and other six pairs successively on the second to seventh abdominal segments. As the larval development proceeds, a brown patch (the midgut of parasitoid larva) in the center of host aphid abdomen becomes larger in size and darker in color. The host aphid turns entirely black as a mummy and dies at the prepupal stage of the parasitoid, pine-nut shaped meconium is excreted at this time. The life cycle of A. maculatus from eggs to adults lasts 11.5–14 days at the temperature of 26 ± 1 °C. Morphological features of mandibles, respiratory spiracles and meconium are useful in the larval taxonomy of aphelinids.

Plant silicon application alters leaf alkaloid concentrations and impacts parasitoids more adversely than their aphid hosts.

Grasses accumulate large amounts of silicon (Si) which acts as a highly effective physical defence against insect herbivory, however recent evidence shows that Si supplementation also modifies plant secondary metabolite concetrations. Changes in plant secondary metabolites concentrations can have cascading effects on higher trophic levels, such as parasitoids, as they are dependent on the host herbivore for growth and development. However, relatively little is known about how Si application affects higher trophic levels. We examined the effects of Si addition on alkaloid content in leaves of Phalaris aquatica (Poaceae) and the effect on interactions between an aphid (Rhopalosiphum padi) and its parasitoid (Aphidius colemani). Si supplementation had no effect on aphid abundance or parasitism rate. Adult aphids, aphid mummies (parasitised aphids) and the emergent parasitoids were, however, significantly smaller on Si+ plants. Parasitoid traits (size and emergence) were correlated with aphid mummy size. Si addition reduced parasitoid emergence rate and size due to reduced host mummy size, in addition, significantly fewer females emerged from mummies on Si+ plants. Aphid infestation significantly altered alkaloids concentrations, reducing gramine by 80% while increasing tryptamine by 91% in Si- plants. Si addition reduced aphid-induced tryptamine concentrations by 64% and increased 5-MeO-tryptamine by over 800% in control and 142% in aphid infested plants. Our results show that while Si addition has modest impacts on the herbivore, it significantly alters secondary metabolites and has stronger effects on the higher trophic level through changes in the quality of the parasitised host.

The boom and bust of the aphid's essential amino acid metabolism across nymphal development.

Within long-term symbioses, animals integrate their physiology and development with their symbiont. In a model nutritional mutualism, aphids harbor the endosymbiont, Buchnera, within specialized bacteriocyte cells. Buchnera synthesizes essential amino acids (EAAs) and vitamins for their host, which are lacking from the aphid’s plant sap diet. It is unclear if the aphid host differentially expresses aphid EAA metabolism pathways and genes that collaborate with Buchnera for the production of EAA and vitamins throughout nymphal development when feeding on plants. It is also unclear if aphid bacteriocytes are differentially methylated throughout aphid development as DNA methylation may play a role in gene regulation. By analyzing aphid gene expression, we determined that the bacteriocyte is metabolically more active in metabolizing Buchnera’s EAAs and vitamins early in nymphal development compared to intermediate or later immature and adult lifestages. The largest changes in aphid bacteriocyte gene expression, especially for aphid genes that collaborate with Buchnera, occurred during the 3rd to 4th instar transition. During this transition, there is a huge shift in the bacteriocyte from a high energy “nutrient-consuming state” to a “recovery and growth state” where patterning and signaling genes and pathways are upregulated and differentially methylated, and de novo methylation is reduced as evidenced by homogenous DNA methylation profiles after the 2nd instar. Moreover, bacteriocyte number increased and Buchnera’s titer decreased throughout aphid nymphal development. These data suggest in combination that bacteriocytes of older nymphal and adult lifestages depend less on the nutritional symbiosis compared to early nymphal lifestages.

Molecular identification of three aphid parasitoids, Aphidius areolatus, A. absinthii, and A. uzbekistanicus (Hymenoptera: Braconidae) from Ulleungdo and Dokdo Islands in Korea

The Ulleungdo and Dokdo Islands are located in the East Sea of Korea and have a unique ecosystem. We collected Aphidiinae mummies from the Ulleungdo and Dokdo Islands in 2018. Three species of parasitoids in the genus Aphidius Nees, A. absinthii Marshall, A. areolatus Ashmead, and A. uzbekistanicus Luzhetzki, were identified using morphological characteristics and molecular techniques from the mummies of three aphid host species Macrosiphoniella formosartemisiae Takahashi, Capitophorus elaeagni (Del Guercio), and Aphis rumicis Linnaeus, respectively. The comparison of the nucleotide sequences of mitochondrial cytochrome c oxidase subunit I in the GenBank database revealed that A. uzbekistanicus was 100% identical to 135 sequences of the species from Asian, American, and European countries and a one-nucleotide variation from a Serbian specimen. Aphidius absinthii was 100% identical to a Japanese specimen of the species and 0.39% variable from the Serbian specimen. However, the cytochrome c oxidase subunit I sequence of A. areolatus did not match in the database and was first reported from this study. Our phylogenetic analysis of 31 Aphidius and 3 Euaphidius species listed in the GenBank database indicated a monophyletic taxon within 12.72% variation. This study is the first report of the geographic distribution of three Aphidius species in the Ulleungdo and Dokdo Islands of Korea. • Aphidiinae mummies were collected from the Ulleungdo and Dokdo Islands in 2018. • Host aphids and enclosed parasitic wasps were identified using morphological and molecular techniques. • Three parasitoid species in the genus Aphidius , A. absinthii , A. areolatus , and A. uzbekistanicus , were identified from three aphid host species Macrosiphoniella formosartemisiae , Capitophorus elaeagni , and Aphis rumicis , respectively. • We provide new information of the distribution of three Aphidius species in the Ulleungdo and Dokdo Islands of Korea.

Increase in Importance of Aphelinus nigritus (Howard) on Winter Crops in Oklahoma Coincides with Invasion of Sugarcane Aphid on Sorghum in Oklahoma

Aphid parasitoids on the Southern Great Plains provide important pest suppression services in summer and winter crops. The primary parasitoids Lysiphlebus testaceipes (Cresson), Aphelinus nigritus (Howard), and Diaretiella rapae (McIntosh) use multiple aphid host species on multiple crops in agricultural landscapes and historically, L. testaceipes has been the most abundant and arguably most important. However, after the sugarcane aphid, Melanaphis sacchari (Zehntner), infested sorghum (Sorghum bicolor (L.) Moench) on the Southern Plains, A. nigritus increased in abundance and impact on this summer crop. We hypothesized that A. nigritus also would be more abundant in fields of winter wheat (Triticum aestivum L.) and winter canola (Brassica napus L.) in the region following the sugarcane aphid. From 2016-2019, we documented aphid parasitoid abundance and percentage of parasitism in Oklahoma winter crops during late fall and early spring using a standardized sentinel aphid deployment retrieval and rearing approach. Unexpectedly, A. nigritus was relatively abundant during Fall 2016, parasitizing as many as 5.4% of sentinel aphids in winter wheat fields which was more than the typically dominant parasitoid L. testaceipes. However, percentage of parasitism by A. nigritus decreased during the study. Our results suggested that abundance of A. nigritus mirrored those of sugarcane aphids in the region, and the temporary presence of the parasitoid in winter crops reflected dynamics at a landscape level.