Aphid Colonies Research Articles

Artificial microRNA-Based RNA Interference and Specific Gene Silencing for Developing Insect Resistance in Solanum lycopersicum

RNA Interference (RNAi), which works against invading nucleic acids or modulates the expression of endogenous genes, is a natural eukaryotic regulating system, and it works by noncoding smaller RNA molecules. Plant-mediated gene silencing through RNAi can be used to develop plants with insect tolerance at transcriptional or post-transcriptional levels. In this study, we selected Myzus persicae’s acetylcholinesterase 1 gene (Ace 1) as a silencing target to develop transgenic Solanum lycopersicum L. plants’ resistance to aphids. An RNAi plasmid vector containing an artificial microRNA (amiRNA) sequence was engineered and successfully transformed into Jamila and Tomaland, two elite tomato cultivars. A northern blot analysis and PCR were carried out to check the efficacy of Agrobacterium-mediated transformation in T0 transgenic plants. The quantitative PCR data showed a substantial downregulation of the Ace 1 gene in aphids fed in clip cages on T1 transgenic plants. Furthermore, there was a substantial drop in aphid colonies that were fed on T1 transgenic plants of both the cultivars. These findings strongly suggest that transgenic plants that express amiRNA could be an important tool for engineering plants resistant to aphids and possibly for the prevention of viral disease in other plant-infested pests.

Research of Aphididae of Cereals and Legumes of the Northeastern Ukraine.

Introduction. The article presents the results of research to establish the species composition of aphids –pests of cereals and legumes of agricultural farm of Kharkov region and analyzes their ecological and biological features. The research was conducted for several years in the spring and summer in the Kupyansk district, Kharkov region. A study of constant changes in the species composition of aphidofauna and recommendations for regulating the number of pests is very relevant today.Purpose.The purpose of the study is to investigate the composition of aphidofauna species of cereals and legumes today and to study the dynamics of the abundance of common species in the field of research.Methods.Inspection of infected plants, determination of the degree of colonization by aphids of each plant. Collecting aphids and determining their species.Results. Thirteen species of aphids of the family Aphididae have been collected and identified. Among the cultivated plants, fields sown with 14 species of cereals and legumes were surveyed. By type of food, certain species of aphids are conditionally divided into oligophages (5 species) and polyphages (8 species). In the aphidofauna of Ukraine, monoecious (non-migratory) life cycles are typicalfor 6 species (46% of the total number), dioecious (migratory) for 7 species (54%) of aphids. The largest number of aphid colonies was recorded on cereals and legumes at the edges of fields bordering on separate strips of woody-shrub and herbaceous vegetation, which serves as an additional forage base or primary host in the dioecious life cycle of some species. Significant aphid damage to cereals was observed during the end of milky –the beginning of waxy ripeness of grain, on the tops of shoots on corn, and in legumes –during the entire growing season on young leaves and stems. As for climatic factors, there was an increase in the number of aphids on cereals in hot dry weather, and on legumes –in moderately warm and humid. Heavy rains suppressed the rapid reproduction and development of all species of aphids. Conclusion.As a result of research, 13 species of aphids of the family true aphids Aphididae were found and identified.The most numerous were polyphagous aphids: the large cereal aphid Sitobion avenae Fabricius, 1775, the common cereal aphid Schizaphis graminum Rondani, 1852, the barley aphid Brachycolus noxius Mordvilko, 1913, the bird-cherry-cereal aphid Rhopalosiphum padi Linnaeus, 1758, elm-cereal, or corn aphid Tetraneura ulmi Linnaeus, 1758, beet-leaf aphid Aphis fabae Scopoli, 1763, pea aphid Acyrthosiphon pisum Harris, 1776.Key words: aphids; aphid fauna; cereals; legumes; oligophagеs; polyphagеs

Spatiotemporal analysis of distribution of pest and predator in corn crops

ABSTRACT Crop pests have negative impacts on yield. This paper proposes a spatiotemporal geostatistical modeling to compare data of adult Syrphidae fly count and corn leaf aphid Rhopalosiphum maidis (Fitch, 1856) colonies in corn crops. The use of a geostatistical model that allows the space-time variation makes the approach more interesting because it is a more complete model. Multiple regression was used to model the trend component for the variable response adult Syrphidae fly count and corn leaf aphid colonies, with the coordinates serving as covariates and the spatiotemporal variations around the deviation are described by a random spacetime residual field. Finally, the prediction map obtained by kriging may be a biological indicator of possible corn leaf aphid colonies in the corn crop. It was possible to verify that the occurrence of the pest provided a significant increase in adult predators and seminatural habitats may favor populations of natural enemies.

Aphid colony duration does not limit the abundance of Harmonia axyridis in the mediterranean area

There is a lot of information on the factors limiting the distributions of species in their native areas, but much less on those limiting potential changes in distributions of species that are currently spreading outside their present range, especially invasive species. However, this information is often quite essential, as it enables the prediction of future spatial distributions and local abundances of invasive species and the potential effect they may have on people and crops. Arising from glasshouse escapes in North America and the Netherlands, the invasive ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), originally from the east Palearctic, has now spread across the whole of North America and most of Europe, both of which caused serious concern. Recent observations show that the spread of H. axyridis towards the equator is limited. For example, it is quite rare in the Mediterranean area and its northward spread in South America is also quite slow, as if there was something limiting its spread towards the equator. European literature indicates it is neither climate, nor the distance of the Mediterranean from the original release location in the Netherlands. Therefore, we hypothesized that it may be biotic factors. In particular, the duration of colonies of prey (colony is the set of individuals in one patch, usually on one plant) that becomes shorter as one approaches the equator. This may lower the fitness of the predator and subsequently lead to low population densities. We test here, whether the duration of aphid colonies is shorter in the Mediterranean area than in Central Europe. Unfortunately, our data does not support this hypothesis. Therefore, the question of what limits the distribution of H. axyridis towards the equator remains to be resolved.

Early snowmelt reduces aphid abundance (Aphis asclepiadis) by creating water-stressed host plants (Ligusticum porteri) and altering interactions with ants

Declining snow cover is reshaping ecological communities. Early loss of snow cover initiates changes in key interactions that mediate herbivore abundance, i.e., top-down and bottom-up effects. In this study, we used a field experiment to test the effects of host plant water stress and phenology on the multitrophic interactions that determine aphid abundance. The aphid, Aphis asclepiadis, in our study system colonizes the flowering stalks of the host plant Ligusticum porteri and relies on a protection mutualism with ants. We added snow and water to replicate host plants and tested for a variety of phenological and physiological responses to these treatments. Relative to host plants in ambient conditions, both water and snow addition reduced key signals of water stress (senescence and abscisic acid levels) and increased seed set. While aphid colonies were generally larger with reduced host plant water stress, the ant–aphid mutualism interacted with plant quality in complex ways. Without ant tending, we did not detect differences in aphid colony growth with host plant treatment. When tended by ants, aphid colony growth was greatest on host plants with snow addition. Host plant quality also altered the benefits exchanged in this mutualism. Ant-tended colonies hosted by plants with snow addition produced honeydew enriched in trehalose, which may have decreased both ant and natural enemy abundance. Our results suggest that early loss of snow reduces aphid abundance by creating low-quality, water-stressed host plants, and this effect may be exacerbated by natural enemies and the costs of ant attendance.

Limited Occurrence of Tristeza in Yuzu and Possible Tristeza-free Cultivation in Northernmost Commercial Yuzu-producing Areas of Japan

Citrus tristeza virus (CTV) commonly infects yuzu (Citrus junos) in most parts of the citrus-growing areas in Japan. This study examined the occurrence of CTV in the northernmost commercial citrusproducing areas of Japan. Colonies of the brown citrus aphid (Toxoptera citricidus) were detected within the areas investigated. However, 23 of the 41 trees that were examined by RT-PCR and both or either subject to stem-pitting observation and immunostrip testing were free of CTV. Several CTVfree trees were apparently more than 60 years old. A field trial revealed that all eight uninoculated seedlings tested negative for CTV at 52 months after transplanting. These results suggest that CTVfree yuzu production is possible in the Rikuzen-Takata and Ofunato areas of Japan.

Corrigendum

New PhytologistVolume 229, Issue 2 p. 1177-1177 CorrigendumFree Access Corrigendum This article corrects the following: Cypripedium subtropicum (Orchidaceae) employs aphid colony mimicry to attract hoverfly (Syrphidae) pollinators Hong Jiang, Ji-Jun Kong, Hsin-Chun Chen, Zhen-Yong Xiang, Wei-Ping Zhang, Zhou-Dong Han, Pei-Chun Liao, Yung-I Lee, Volume 227Issue 4New Phytologist pages: 1213-1221 First Published online: May 22, 2020 First published: 24 September 2020 https://doi.org/10.1111/nph.16889 Author for correspondence: Yung-I Lee Tel:+886 4 23226940 ext. 153 Email:[email protected] AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL New Phytologist 227 (2020), 1213–1221, doi: 10.1111/nph.16623 Since its publication, the authors of Jiang et al. (2020) have brought to our attention an error in their article. The species of hoverfly detailed in the legend Fig. 2(a,b) and (c,d) were transposed. The correct Fig. 2 legend is shown below. Fig. 2Open in figure viewerPowerPoint A pollination system in Cypripedium subtropicum. (a) Eupeodes confrater eating hair tufts. Bar, 3 mm. (b) The body of E. confrater has contacted the anther. Bar, 3 mm. (c) Eristalinus arvorum eating hair tufts. Bar, 3 mm. (d) The body of E. arvorum has contacted the anther. Bar, 3 mm. (e) Dissected flower with half the labellum removed. The dotted line indicates the pollination route and direction of fly movement. Bar, 10 mm. (f) Cryo-scanning electron microscopy (SEM) image of a few cells from white hair tufts (arrow) on the mouthparts of a trapped hoverfly. Bar, 100 μm. We apologize to our readers for this mistake. Reference Jiang H, Kong J-J, Chen H-C, Xiang Z-Y, Zhang W-P, Han Z-D, Liao P-C, Lee Y-I. 2020. Cypripedium subtropicum (Orchidaceae) employs aphid colony mimicry to attract hoverfly (Syrphidae) pollinators. New Phytologist 227: 1213– 1221. Volume229, Issue2January 2021Pages 1177-1177 FiguresReferencesRelatedInformation

Resistance among selected wild soybean and associated soybean accessions against two virulent colonies of Aphis glycines (Hemiptera: Aphididae)

The soybean aphid (Aphis glycines) is an important pest of soybean (Glycine max). Wild soybean (Glycine soja; also known as ‘soja’) has many useful traits, including some accessions with aphid resistance that may be incorporated into modern soybean cultivars. The objective of this work was to evaluate 76 selected soja accessions and 14 associated soybean accessions for resistance against two virulent colonies of soybean aphid in environmental-chamber experiments. In free-choice tests, soja accessions PI 407175, PI 407190, PI 407206, PI 407240, PI 507624 and PI 562558 were resistant against the Accrue colony, and PI 407191wf and PI 597458 C were resistant against the Volga16 colony. None of the soybean test accessions except the resistant check, PI 437696, showed resistance against either colony in free-choice tests. In no-choice tests, soja accession PI 507624 showed strong resistance against the Accrue colony; whereas PI 407240 and PI 407190 had intermediate aphid levels; PI 597458 C showed strong resistance to Volga16 aphids, and PI 407191wf had an intermediate level of resistance. Based on results from both sets of tests, soja accessions PI 507624 and PI 597458 C may be strong candidates in breeding programs to develop aphid-resistant soybean cultivars.

Local adaptation and rapid evolution of aphids in response to genetic interactions with their cottonwood hosts.

Several studies have demonstrated the ecological consequences of genetic variation within a single plant species. For example, these studies show that individual plant genotypes support unique composition of the plants' associated arthropod community. By contrast, fewer studies have explored how plant genetic variation may influence evolutionary dynamics in the plant's associated species. Here, we examine how aphids respond evolutionarily to genetic variation in their host plant. We conducted two experiments to examine local adaptation and rapid evolution of the free‐feeding aphid Chaitophorus populicola across genetic variants of its host plant, Populus angustifolia. To test for local adaptation, we collected tree cuttings and aphid colonies from three sites along an elevation/climate gradient and conducted a reciprocal transplant experiment. In general, home aphids (aphids transplanted onto trees from the same site) produced 1.7–3.4 times as many offspring as foreign aphids (aphids transplanted onto trees from different sites). To test for rapid evolution, we used 4 clonally replicated aphid genotypes and transplanted each onto 5 clonally replicated P. angustifolia genotypes. Each tree genotype started with the same aphid genotype composition. After 21 days (~two aphid generations), aphid genotype composition changed (i.e., aphids evolved) and some tree genotypes supported unique evolutionary trajectories of aphids. These results suggest that plant evolution in response to human perturbation, such as climate change and invasive species, will also result in evolutionary responses in strongly interacting species that could cascade to affect whole communities.

Preliminary assessment of selected sweet cherry hybrids regarding their resistance to black cherry aphid (Myzus cerasi Fabr.) in Bulgaria

Abstract. One of the main insect pests of the cherry trees in Bulgaria is Myzus cerasi (Homoptera, Aphididae). The black cherry aphids occur annually in orchards and cause yield loss or degraded quality. In 2018 and 2019, resistance to Myzus cerasi was assessed on 11 selected sweet cherry genotypes in a breeding orchard at the Fruit Growing Institute – Plovdiv. Susceptibility to aphid infestation was assessed through inspection of 100 leaf rosettes from individual tree hybrids. Some of the studied genotypes 6-132, 6-132 (1), 6-131, and 6-131 (1) were not infested by black cherry aphids in the two years of this research. Aphid colonies were observed on all other studied trees from the selected hybrids. The study is still ongoing.

Sight unseen: Belowground feeding influences the distribution of an aboveground herbivore

AbstractPlants are under constant threat from insect herbivores that can consume all types of plant tissue, both aboveground and belowground. Because plants connect aboveground and belowground environments, they are uniquely positioned to mediate indirect herbivore interactions between the two ecosystems. The effects of this mediation may change over time with cascading consequences both aboveground and belowground. We used a system involving the larval belowground (BG) herbivore Diabrotica speciosa (Coleoptera: Chrysomelidae), corn, and the aphid aboveground (AG) herbivore Rhopalosiphum maidis to answer three questions: (1) What effects does belowground herbivory by D. speciosa have on feeding preferences and distributions of the aboveground R. maidis? (2) How do these preferences and distributions change over time? And (3) what are the longer term consequences for R. maidis populations? Adult alate aphids initially preferred corn seedlings with root feeding by D. speciosa, but preference declined over time driven by aphids leaving corn seedlings with root herbivory. Similarly, observations of aphid performance and colony growth indicated negative effects of root herbivory in contrast to previous studies. These results suggest that shifts in plant‐mediated aboveground–belowground interactions can have important consequences for long‐term distributions of aboveground herbivores.

Does combining Forficula auricularia L. (Dermaptera: Forficulidae) with Harmonia axyridis Pallas (Coleoptera: Coccinellidae) enhance predation of rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae)?

A good knowledge of interactions between natural enemy species is necessary for effective implementation of biological control programmes. This laboratory study aimed at assessing the outcome of intraguild interactions between two generalist predators frequently observed in the colonies of the rosy apple aphid (RAA), Dysaphis plantaginea Passerini (Hemiptera: Aphididae). The level of complementarity between these two species was estimated by the comparison of their individual and combined predation on RAA. Predation by 1st (H1) to 4th (H4) instar larvae of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and 3rd (F3) and 4th (F4) instar nymphs of Forficula auricularia L. (Dermaptera: Forficulidae) was evaluated for 24 h in Petri dishes using seven different densities (5, 10, 25, 50, 75, 100 and 200) of 3rd instar nymphs of RAA. Both predator species were more voracious as their age increased. The satiation level, i.e. the highest number of consumed RAA, reached on average of 17.8, 36.3, 49.4, 79.6, 62.9 and 84.3 aphids per day for H1, H2, H3, H4, F3 and F4, respectively. In the combined treatments, there was little evidence of intraguild predation. Only 2.9% of H1 and H2 died or disappeared at low RAA densities (≤25 aphids). At the non-limiting RAA density of 200, we observed a slight agonistic interaction with 7.9% less RAA consumption when the two predators were in the same arena than the sum of their individual consumptions. However, this effect was very small and was largely outweighed by the benefits of using these two predators in combination to increase prey consumption. For the other six RAA densities, predators in combination consumed a high proportion (>90%) of RAA. Our results point to the use of combinations of these two predator species, especially of their oldest instars, as promising aphidophagous candidates in early spring against RAA.

Aphid predators in citrus crops: the least voracious predators are the most effective

Rich and abundant predator complexes are frequently associated with aphids in perennial agroecosystems. The ability of these predators to successfully suppress aphid populations is nevertheless highly variable. The development of operative conservation biological control strategies is mostly hindered by the lack of knowledge of the specific roles of the aphidophagous assemblage components, their intra-guild relationships and the predatory attributes that chiefly determine their effectiveness. The role of predation in the biological control of aphids in perennial agroecosystems was assessed through exclusion experiments in aphid infested citrus crops. Important predator attributes such as recruitment, aphid consumption rates, and foraging strategies were related to their efficacy. Predation greatly affected aphid colony phenology as well as size. Predators with lower aphid consumption rates (Micro-coccinellid species and Cecidomyiidae) were revealed to be the most efficient aphidophaga. These predators encountered aphid colonies at earlier colony stages and significantly reduced their population growth rates. Later more voracious aphidophaga groups (Chrysopidae and Macro-coccinellids) did not present effective biological control of the colonies. Contrarily to what was widely believed, the less voracious aphidophaga groups such as the Micro-coccinellids and Cecidomyiids are probably the groups who are mostly responsible for aphid suppression. Future conservation biological control studies in this crop should therefore chiefly focus on these groups.

Seasonal incidence and bionomics of rose aphid, Macrosiphum rosae (Linnaeus, 1758), (Hemiptera: Aphididae) in Kashmir, India

Rose is the principal flower of the world floriculture industry that is being exclusively used as cut flower, potted plant and garden plant. It plays significant part in numerous industries viz. food, perfumery and cosmetic industries. About 96 % of women’s perfumes contain true Bulgarian rose oil. Roses are well acclimatized in Jammu & Kashmir because of its suitable agro climatic conditions which can permit its large scale production and rose products produced in the state are at par with the international standards. But the aesthetic and commercial value of roses is greatly lowered by numerous insect pests resulting in low yield. However, its major pest include aphid species most notoriously Macrosiphum rosae that pose many challenges and threats to rose plant cultivation. Aphid colonies on roses result in reduction of medical value of the plant and cause economic losses to growers particularly during spring and summer season. In order to reduce the economic losses inflicted by rose aphid, it is necessary to study different biological parameters of this pest species so that an effective management plan can be formulated.

Plant Silicon Amendment Does Not Reduce Population Growth of Schizaphis graminum or Host Quality for the Parasitoid Lysiphlebus testaceipes.

Interactions between different pest control methods can affect Integrated Pest Management efficiency. This study sought to evaluate (1) if Si accumulation is related to the level of constitutive resistance in sorghum genotypes, (2) the level of Si induces resistance by antibiosis in sorghum genotypes with different levels of constitutive resistance to Schizaphis graminum (Rondani) (reared individualized or in colonies), and (3) the fitness of Lysiphlebus testaceipes (Cresson) in aphids reared on Si-treated and untreated plants. Several experiments were conducted under greenhouse conditions, using sorghum genotypes with different levels of resistance grown in pots with or without the addition of Si to the soil. The susceptible (BR007B), moderately resistant (GB3B), and highly resistant (TX430XGR111) genotypes all absorbed more Si when it was added to the soil compared with when it was not amended. However, the final Si content of treated plants was not related to the level of constitutive resistance among treated genotypes. While Si soil application did reduce the fecundity of individualized aphids reared on the susceptible and moderately resistant sorghum plants, it did not reduce populational growth of aphid colonies, independent of the level of plant's constitutive resistance. Parasitoid (L. testaceipes) had higher weight when reared from aphids fed on plants with added Si. Sorghum × constitutive resistance × S. graminum interactions were affected by plant Si content only for individualized aphids but not for aphid colonies. Sorghum × S. graminum × L. testaceipes interactions suggest that Si can have, overall, a positive effect on the biological control of S. graminum.

Cypripedium subtropicum (Orchidaceae) employs aphid colony mimicry to attract hoverfly (Syrphidae) pollinators.

In Orchidaceae, pollination is mostly animal-mediated, and one-third of species have evolved a deceptive pollination mechanism without rewards. Cypripedium is a representative lineage of nonrewarding orchids restricted to temperate regions. Cypripedium subtropicum flowers are pollinated by hoverflies and have hairy tufts that visually resemble an aphid colony covered with honey dew. We recorded the behavior of hoverflies on the flowers, determined the breeding system of the species and the structure of hairy tufts, and investigated the roles of hairy tufts and floral volatiles in this specialized pollination by using pollination experiments, scanning electron microscopy, bioassays and chemical analyses. The white hairy tufts covering the sidelobes of the labellum provide edible rewards and serve as crucial visual lures for hoverflies. The flowers emit primarily (E)-β-farnesene and a smaller amount of β-pinene that were found to attract hoverflies. Our results suggest that C.subtropicum uses both visual mimicry of an aphid-colonized labellum with a reward and chemical mimicry of aphid alarm pheromones to attract hoverflies for pollination. This is the first described example of a rewarding mimicry system in plants, where the models are animals with their secretions and the reward is similar in nutrients to that of the model mimicked.

Advanced phenology of intraguild predators shifts herbivore host plant preference and performance

1. The abundance of insect herbivores is mediated by interactions with higher and lower trophic levels. This research asks (i) how phenological change across trophic levels affects host plant quality and selection for aphids, and (ii) what higher trophic level mechanisms drive aphid abundance.2. Ligusticum porteri is a perennial host for the sap‐feeding aphid Aphis asclepiadis and intraguild mirid predators (chiefly Lygus hesperus) in Colorado. We used long‐term observational data to discover that aphids and mirids respond differently to phenological cues. These unique responses can impact aphid abundance through changes to host plant selection and quality.3. We used behavioural choice assays to assess how advanced mirid phenology influences aphid host plant selection. More alates landed and reproduced on mirid‐free control plants relative to host plants with prior mirid feeding. However, this preference did not correlate with aphid performance when we compared aphid relative growth rates between treatments. This suggests that advanced mirid phenology would impact aphid populations more through host plant choice, rather than reductions in host quality. The addition of mirids to experimental aphid colonies also demonstrated reduced aphid colony growth via predation.4. We measured plant cues involved in host selection and found differences in volatile composition between plants with prior mirid feeding compared to control plants, providing the potential for aphids to detect enemy‐free space using volatile cues.

The recombinant isolate of cucurbit aphid‐borne yellows virus from Brazil is a polerovirus transmitted by whiteflies

AbstractThe severe yellowing disease (amarelão) on melon plants is a serious problem in Brazil, although the causative agent remained unknown for a long time. Recently, recombinant isolates of cucurbit aphid‐borne yellows virus (CABYV) were reported as the possible causative agents of this disease on melon plants. Although aphids are known to be the vectors of the common type of CABYV isolates, almost no aphid colony was observed in the major melon fields in Brazil with high incidence of the severe yellowing disease. In contrast, whiteflies are often abundant. Based on this observation, the hypothesis of the transmission of recombinant CABYV by whiteflies was evaluated. After thorough transmission experiments, we found that this recombinant CABYV isolate was transmitted by the whitefly Bemisia tabaci MEAM1, but not by Aphis gossipii. Furthermore, the host response by whitefly‐based inoculation in cucurbits and other indicator plants showed differences in host range when compared to the common type of CABYV. Due to its transmissibility by the whitefly and the distant relationship of the P3/P5 protein to CABYV, the name “cucurbit whitefly‐borne yellows virus” is proposed for this recombinant CABYV. This is the second report of polerovirus transmission by the whitefly B. tabaci, following the report of pepper whitefly‐borne vein yellows virus.

First Report and Distribution of the Indian Mustard Aphid, Lipaphis erysimi pseudobrassicae (Hemiptera: Aphididae) on Cabbage (Brassica oleracea var capitata) in Ghana

The presence of large colonies of aphids is associated with a devastating novel necrotic disease of cabbage (Brassica oleracea var. capitata) in Ghana that is thought to be of viral etiology. In this study, we used molecular taxonomic tools to identify the aphid species present on these diseased cabbage plants. This was confirmed using two key features for morphological identification, involving the length of cornicles and shape of cauda for the wingless forms of the aphids. Two species of aphids were identified and their distribution in Ghana indicated. One was the generalist aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) but the most abundant was the brassica specialist aphid, Lipaphis erysimi pseudobrassicae (Davis) (Hemiptera: Aphididae), which is one of the most destructive pests of brassica crops in some countries in Africa and other parts of the world. L. erysimi has been reported in Benin, Mali, South Africa, India, China, and United States, but this is the first formal report of L. erysimi pseudobrassicae in Ghana. The correct identification of L. erysimi is crucial, suggesting that it has recently become one of the most common species of aphid found on cabbage plants in Ghana.

Spatial behavior of corn leaf aphid and syrphid flies in corn crop in the northeast of Pará

The aim of this study was to verify the spatial and temporal behavior of corn leaf aphid (Rhopalosiphum maidis Fitch.) and hoverflies in corn crop in the municipality of Igarapé-Açu, northeast of Pará, Brazil, as well as the influence of adjacent areas on the occurrence of these insects. An experimental area of 1.0 ha (100 x 100 m) was used in the years 2015 and 2016, adjacent areas consisted of mango agroecosystem, pasture and secondary forest. The area was divided into grid with 100 plots of 100 m² (10 x 10 m). Ten plants were randomly selected, totaling 1,000 plants per sampling date. Corn leaf aphid colonies (= or> 15 aphid) and syrphid flies adult was visually analyzed throughout the aerial parts of the plants. The spatial behavior was analyzed by semivariogram modeling and kriging interpolation maps. The semivariograms and kriging maps were made by the R software for Windows. Gaussian, spherical and exponential models were the best fit for corn leaf aphid in both harvests, showing aggregate behavior. The strong and moderate spatial dependence index prevailed, with range ranging from 12.46 to 93.04 m for R. maidis. The syrphids flies showed spatial interaction with the corn leaf aphid and they also show aggregate behavior, confirmed by most adjustments in the spherical and exponential models. The spatial dependence index of the prevailing syrphids flies were moderate and weak, ranging from 14.00 to 101.33 m. Adjacent areas showed influence on occurrence and dispersal of both corn leaf aphid and syrphids flies.