Rhopalosiphum Maidis Research Articles

Incidence and distribution of insect pests in rain-fed wheat in eastern Africa

Insect pests are some of the major constraints limiting yield of wheat ( Triticum aestivum L.) in East Africa. The objective of this study was to determine the species composition and distribution of insect pests, and their natural enemies associated with wheat in Eastern Africa. A survey was conducted in farmers’ fields in Ethiopia, Kenya and Uganda during 2013 and 2014 cropping season. Wheat fields along roadsides were randomly selected at approximately 2 to 10 Km intervals, and in each field, several wheat plants in a cross diagonal line were examined for presence or absence of insect pests and associate natural enemies. Also, the type of insect was identified to species level and in situ population counts recorded. In Ethiopia, only 39% of the fields were infested by tef epilachna, Chnootriba similis Thurnberg (Coleoptera: Coccinellidae); while the remaining wheat fields were free of insect infestation. The Russian Wheat Aphid (RWA), Diuraphis noxia Kurdijumov (Hemiptera: Aphididae), was the most prevalent insect pest of wheat in Kenya and Uganda. The maximum number of RWA per tiller was 58 in Kenya and 38 in Uganda. Moreover, in Kenya the rose wheat (grass) aphid ( Metopolophium dirhodum Walker), oat-bird-cherry aphid ( Rhopalosiphum padi Walker) and corn leaf aphid (R. maidis Fitch) were prevalent, though at low densities ranging, from 0.1 to 9 per tiller. The greenbug ( Schizaphis graminum Rondani) and the green stink bug ( Nezara viridula L.) were recorded only in Uganda. The general aphid predators Cheilomenes spp., spiders, lacewings and the parasitoid Aphidius spp. were the natural enemies of aphids found in Kenyan wheat. However, the density of these natural enemies was too low to bring the aphid population to a level that causes economic damage. Key Words: Russian Wheat Aphid, Triticum aestivum

Incidence and distribution of insect pests in rain-fed wheat in eastern Africa

Insect pests are some of the major constraints limiting yield of wheat (Triticum aestivum L.) in East Africa. The objective of this study was to determine the species composition and distribution of insect pests, and their natural enemies associated with wheat in Eastern Africa. A survey was conducted in farmers’ fields in Ethiopia, Kenya and Uganda during 2013 and 2014 cropping season. Wheat fields along roadsides were randomly selected at approximately 2 to 10 Km intervals, and in each field, several wheat plants in a cross diagonal line were examined for presence or absence of insect pests and associate natural enemies. Also, the type of insect was identified to species level and in situ population counts recorded. In Ethiopia, only 39% of the fields were infested by tef epilachna, Chnootriba similis Thurnberg (Coleoptera: Coccinellidae); while the remaining wheat fields were free of insect infestation. The Russian Wheat Aphid (RWA), Diuraphis noxia Kurdijumov (Hemiptera: Aphididae), was the most prevalent insect pest of wheat in Kenya and Uganda. The maximum number of RWA per tiller was 58 in Kenya and 38 in Uganda. Moreover, in Kenya the rose wheat (grass) aphid (Metopolophium dirhodum Walker), oat-bird-cherry aphid (Rhopalosiphum padi Walker) and corn leaf aphid (R. maidis Fitch) were prevalent, though at low densities ranging, from 0.1 to 9 per tiller. The greenbug (Schizaphis graminum Rondani) and the green stink bug (Nezara viridula L.) were recorded only in Uganda. The general aphid predators Cheilomenes spp., spiders, lacewings and the parasitoid Aphidius spp. were the natural enemies of aphids found in Kenyan wheat. However, the density of these natural enemies was too low to bring the aphid population to a level that causes economic damage.Key Words: Russian Wheat Aphid, Triticum aestivum

Beauveria bassiana em associação com milho geneticamente modificado no manejo de Spodoptera frugiperda e Rhopalosiphum maidis

RESUMO: O objetivo deste trabalho foi avaliar a eficiência do fungo Beauveria bassiana (isolado CG 716) no manejo de Spodoptera frugiperda e Rhopalosiphum maidis em milho. Diante disso, montou-se um experimento em blocos ao acaso, utilizando parcelas subdivididas, contendo dez tratamentos e quatro repetições. Os tratamentos foram: B. bassiana , formulado em óleo vegetal, nas doses de 2,0, 4,0 e 6,0 x 1012 conídios ha-1, lambda-cialotrina (7,5 i.a. ha-1) e testemunha (sem aplicação). As aplicações foram realizadas a partir dos 10 dias após a emergência (DAE) das plantas, sendo repetidas aos 16, 23 e 31 DAE. As avaliações foram realizadas semanalmente coletando-se dez plantas consecutivas por parcela e armazenadas em sacos plásticos, para posterior destruição do cartucho e contagem de lagartas, pulgões e inimigos naturais em laboratório. Não ocorreram diferenças significativas em populações de S. frugiperda e R .maidis em lavouras de milho submetidas ou não a aplicações de defensivos; entretanto, na variedade convencional, aos 40 DAE, foi constatado que um maior número médio pulgõessob aplicação do bioinseticida na dosagem de 2,0 x 1012 conídios ha-1. B. bassiana ,em associação com a tecnologia Bt , não produziu resultados satisfatórios no controle de S. frugiperda e R. maidis nas condições em que foi testado.

Studies on Pest Complex and Seasonal Incidence of Shoot Fly,Atherigona Soccata(Rondani) on Maize in Western U.P.

An investigation to study the pest complex and seasonal incidence of shoot fly, Atherigona soccata (Rondani) in maize was carried out for two consecutive seasons i.e. 2013 and 2014. During the experimentation, eleven insect species were found attacking on different growth stage of maize crop, out of these stem borer, Chilo partellus (Swinhoe) and shoot fly, A. soccata (Rondani) were recorded as major pests, two insect Rhopalosiphum maidis and Pyrilla perpusilla was recorded as stray pests while other seven insects were appeared as minor insects to this region. The peak number of egg laid by shoot fly 2.27 and 2.37 egg/plant were recorded at end week of March (13th Standard Week) during the years, 2013 and 2014, respectively. The peak dead heart caused by shoot fly 26.18 and 26.40 per cent was recorded at first week of April (14th Standard Week) during the both years of experimentation i.e. 2013 and 2014, respectively. In case of shoot fly incidence among the weather factors, only morning and evening relative humidity showed positive correlation while other had negative correlation.

Surveys of Viruliferous Alate Aphid of Plum pox virus in Prunus mume Orchards in Japan.

Plum pox virus (PPV) is transmitted by infected buds and aphids. It is important to analyze the outbreak trends and viruliferous rate of aphids in areas where the occurrence of PPV is reported, so as to develop strategies for disease control. Between April 2011 and December 2012, yellow insect-trapping adhesive plates were placed for 2 days at a time each week in an area where PPV is occurring in Japan. Outbreak trends were analyzed based on the trapped alate aphid samples, and up to 50 of them were tested per week to identify species and determine the rate of viruliferous specimens. Although the number of aphids varied according to survey year, three peaks were noticeable in each year. Based on the sequence data for the mitochondrial cytochrome c oxidase I region, approximately 40 different species of aphid were trapped in both years. Of the five dominant species of aphids identified during the 2 years, Aphis spiraecola was trapped in large numbers. PPV-positive aphids were higher in fall onward, when the total number of trapped aphids decreased, than in spring and summer, when a larger number of aphids was caught. PPV transmission tests using the most abundant species revealed that A. spiraecola, A. craccivora, A. gossypii, and Rhopalosiphum maidis were transmitters, although A. spiraecola is likely of epidemiological significance.

Genetic mapping shows intraspecific variation and transgressive segregation for caterpillar-induced aphid resistance in maize.

Plants in nature have inducible defences that sometimes lead to targeted resistance against particular herbivores, but susceptibility to others. The metabolic diversity and genetic resources available for maize (Zea mays) make this a suitable system for a mechanistic study of within-species variation in such plant-mediated interactions between herbivores. Beet armyworms (Spodoptera exigua) and corn leaf aphids (Rhopalosiphum maidis) are two naturally occurring maize herbivores with different feeding habits. Whereas chewing herbivore-induced methylation of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc) to form 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) promotes caterpillar resistance, lower DIMBOA-Glc levels favour aphid reproduction. Thus, caterpillar-induced DIMBOA-Glc methyltransferase activity in maize is predicted to promote aphid growth. To test this hypothesis, the impact of S. exigua feeding on R. maidis progeny production was assessed using seventeen genetically diverse maize inbred lines. Whereas aphid progeny production was increased by prior caterpillar feeding on lines B73, Ki11, Ki3 and Tx303, it decreased on lines Ky21, CML103, Mo18W and W22. Genetic mapping of this trait in a population of B73 × Ky21 recombinant inbred lines identified significant quantitative trait loci on maize chromosomes 1, 7 and 10. There is a transgressive segregation for aphid resistance, with the Ky21 alleles on chromosomes 1 and 7 and the B73 allele on chromosome 10 increasing aphid progeny production. The chromosome 1 QTL coincides with a cluster of three maize genes encoding benzoxazinoid O-methyltransferases that convert DIMBOA-Glc to HDMBOA-Glc. Gene expression studies and benzoxazinoid measurements indicate that S. exigua -induced responses in this pathway differentially affect R. maidis resistance in B73 and Ky21.

Dynamic Maize Responses to Aphid Feeding Are Revealed by a Time Series of Transcriptomic and Metabolomic Assays.

As a response to insect attack, maize (Zea mays) has inducible defenses that involve large changes in gene expression and metabolism. Piercing/sucking insects such as corn leaf aphid (Rhopalosiphum maidis) cause direct damage by acquiring phloem nutrients as well as indirect damage through the transmission of plant viruses. To elucidate the metabolic processes and gene expression changes involved in maize responses to aphid attack, leaves of inbred line B73 were infested with corn leaf aphids for 2 to 96 h. Analysis of infested maize leaves showed two distinct response phases, with the most significant transcriptional and metabolic changes occurring in the first few hours after the initiation of aphid feeding. After 4 d, both gene expression and metabolite profiles of aphid-infested maize reverted to being more similar to those of control plants. Although there was a predominant effect of salicylic acid regulation, gene expression changes also indicated prolonged induction of oxylipins, although not necessarily jasmonic acid, in aphid-infested maize. The role of specific metabolic pathways was confirmed using Dissociator transposon insertions in maize inbred line W22. Mutations in three benzoxazinoid biosynthesis genes, Bx1, Bx2, and Bx6, increased aphid reproduction. In contrast, progeny production was greatly decreased by a transposon insertion in the single W22 homolog of the previously uncharacterized B73 terpene synthases TPS2 and TPS3. Together, these results show that maize leaves shift to implementation of physical and chemical defenses within hours after the initiation of aphid feeding and that the production of specific metabolites can have major effects in maize-aphid interactions.

Temporal Changes in Cereal Aphids (Hemiptera: Aphididae) Populations in Northern Rio Grande do Sul, Brazil

Cereal aphids (Hemiptera: Aphididae) are economically important pests in all wheat-producing regions of Brazil and about eight species can be found in wheat crops. Aphids acquired the condition of severe pest in wheat in the 1970s, due to the emergence of Metopolophium dirhodum and Sitobion avenae. A successful biological control program of wheat aphids was introduced in southern Brazil in 1978. This study describes temporal changes in aphid populations in a wheat producing area in the northern region of Rio Grande do Sul (RS) state, Brazil. Data from weekly samples (water traps of Moericke type) for the current (May to November 2008, 2009 and 2010) population frequency of each species was compared with 1970s populations. In addition, their seasonal fluctuations and the influence of rainfall and temperature on their populations were estimated. The species collected, and their frequencies, were as follows: Rhopalosiphum padi (57.6%), Sitobion avenae (31.0 %), Schizaphis graminum (7.7%), Metopolophium dirhodum (1.4%), Rhopalosiphum rufiabdominalis (0.9%), Rhopalosiphum maidis (0.6%), Sipha maydis (0.4%) and Sipha flava (0.4%). Aphids populations in winter cereals in northern RS have changed radically. The high populations of M. dirhodum in wheat in 1970s have been reduced to such levels that rarely have been found. Nowadays, R. padi was the predominant species. When the rainfall remained between 0-20 mm and temperatures between 15-20 ºC, aphid populations were more numerous than the average for the sampling period.

Ethylene Contributes to maize insect resistance1-Mediated Maize Defense against the Phloem Sap-Sucking Corn Leaf Aphid.

Signaling networks among multiple phytohormones fine-tune plant defense responses to insect herbivore attack. Previously, it was reported that the synergistic combination of ethylene (ET) and jasmonic acid (JA) was required for accumulation of the maize insect resistance1 (mir1) gene product, a cysteine (Cys) proteinase that is a key defensive protein against chewing insect pests in maize (Zea mays). However, this study suggests that mir1-mediated resistance to corn leaf aphid (CLA; Rhopalosiphum maidis), a phloem sap-sucking insect pest, is independent of JA but regulated by the ET-signaling pathway. Feeding by CLA triggers the rapid accumulation of mir1 transcripts in the resistant maize genotype, Mp708. Furthermore, Mp708 provided elevated levels of antibiosis (limits aphid population)- and antixenosis (deters aphid settling)-mediated resistance to CLA compared with B73 and Tx601 maize susceptible inbred lines. Synthetic diet aphid feeding trial bioassays with recombinant Mir1-Cys Protease demonstrates that Mir1-Cys Protease provides direct toxicity to CLA. Furthermore, foliar feeding by CLA rapidly sends defensive signal(s) to the roots that trigger belowground accumulation of the mir1, signifying a potential role of long-distance signaling in maize defense against the phloem-feeding insects. Collectively, our data indicate that ET-regulated mir1 transcript accumulation, uncoupled from JA, contributed to heightened resistance to CLA in maize. In addition, our results underscore the significance of ET acting as a central node in regulating mir1 expression to different feeding guilds of insect herbivores.

Bioenergy Crops and Natural Enemies: Host Plant-Mediated Effects of Miscanthus on the Aphid Parasitoid Lysiphlebus testaceipes

Miscanthus spp. are biofuel crops that are triggering growing interest worldwide due to their numerous agronomic advantages. Though breeding programs take into account usual key plant traits of agronomic interest (e.g., biomass production, adaptation to broader climatic range), they generally overlook plant attributes relating to pest and pathogen resistance and even more those that may favor or improve the combined use of biological control agents of pests. A recent study showed that the parental species, Miscanthus sacchariflorus and, to a lesser extent, Miscanthus sinensis, were less suitable and acceptable host plants for the corn leaf aphid Rhopalosiphum maidis, one of the main pests of Miscanthus × giganteus in the USA, than the hybrid M. × giganteus. In the present laboratory study, we investigated the host plant-mediated effects of these three miscanthus species on various life history traits of the aphid parasitoid Lysiphlebus testaceipes. A clear host plant effect was shown on aphid size and, consequently, on parasitoid fitness parameters. High plant resistance to aphids was shown to be more detrimental to the parasitoid than partial resistance, with M. sacchariflorus being the least suitable host plant to both aphid and parasitoid development. Selection of partial resistance, such as the one exhibited by M. sinensis, should then be preferred to support efficient aphid regulation by parasitoids. This study provides the first contribution to the evaluation of bottom-up effects of a biofuel crop on beneficial insects. It also underlines the need to conduct additional research when considering the implementation of new biomass crops.

Accumulation of 5-hydroxynorvaline in maize (Zea mays) leaves is induced by insect feeding and abiotic stress.

Plants produce a wide variety of defensive metabolites to protect themselves against herbivores and pathogens. Non-protein amino acids, which are present in many plant species, can have a defensive function through their mis-incorporation during protein synthesis and/or inhibition of biosynthetic pathways in primary metabolism. 5-Hydroxynorvaline was identified in a targeted search for previously unknown non-protein amino acids in the leaves of maize (Zea mays) inbred line B73. Accumulation of this compound increases during herbivory by aphids (Rhopalosiphum maidis, corn leaf aphid) and caterpillars (Spodoptera exigua, beet armyworm), as well as in response to treatment with the plant signalling molecules methyl jasmonate, salicylic acid and abscisic acid. In contrast, ethylene signalling reduced 5-hydroxynorvaline abundance. Drought stress induced 5-hydroxynorvaline accumulation to a higher level than insect feeding or treatment with defence signalling molecules. In field-grown plants, the 5-hydroxynorvaline concentration was highest in above-ground vegetative tissue, but it was also detectable in roots and dry seeds. When 5-hydroxynorvaline was added to aphid artificial diet at concentrations similar to those found in maize leaves and stems, R. maidis reproduction was reduced, indicating that this maize metabolite may have a defensive function. Among 27 tested maize inbred lines there was a greater than 10-fold range in the accumulation of foliar 5-hydroxynorvaline. Genetic mapping populations derived from a subset of these inbred lines were used to map quantitative trait loci for 5-hydroxynorvaline accumulation to maize chromosomes 5 and 7.

Effects of aphid feeding and associated virus injury on grain crops in Australia

We review yield effects caused by aphid feeding and associated virus injury to cereal, oilseed and pulse crops, and estimate the potential economic loss caused by aphids in Australia. Potential yield reduction due to aphids was determined through a survey of quantitative data from experiments that assessed aphids' effect on grain yield. In cereals, four aphids caused damage; on barley, feeding injury caused by Rhopalosiphum padi + Rhopalosiphum maidis was most damaging in terms of yield reduction (25.5%) with an economic loss of $19/ha. Barley yellow dwarf virus transmitted by R. padi + Sitobion miscanthi was more damaging than direct feeding, causing a yield reduction of 39% and economic loss of $21/ha for wheat. On canola, beet western yellow virus transmitted by Myzus persicae caused the highest yield reduction of 34% and economic loss of $115/ha, although this was measured through artificial inoculations. Feeding injury was high in Brevicoryne brassicae which caused an average yield reduction of 34% and associated economic loss of $88.5/ha, while Lipaphis erysimi and M. persicae had negligible economic effects but more data are needed. On pulses, the most economically damaging (unidentified) aphids feeding on lupins caused a yield reduction of 43% and economic loss of $24/ha. The aphids M. persicae + Aphis craccivora + Acyrthosiphon kondoi reduced lupin yields by 13% and economic returns by $7.40/ha. On field peas, a 14% reduction in yield was caused by transmitted viruses such as pea seed-borne mosaic virus which caused economic losses of $20.50/ha. In total, feeding and virus injuries resulted in potential economic costs of $241 and $482 million/year, respectively. Although this review provides estimates of potential yield and economic losses due to aphids, few data were available for some crops, aphid species or regions (e.g. oats). Nevertheless, economic costs associated with aphids appear substantial.

Additive effects of two quantitative trait loci that confer Rhopalosiphum maidis (corn leaf aphid) resistance in maize inbred line Mo17.

Plants show considerable within-species variation in their resistance to insect herbivores. In the case of Zea mays (cultivated maize), Rhopalosiphum maidis (corn leaf aphids) produce approximately twenty times more progeny on inbred line B73 than on inbred line Mo17. Genetic mapping of this difference in maize aphid resistance identified quantitative trait loci (QTL) on chromosomes 4 and 6, with the Mo17 allele reducing aphid reproduction in each case. The chromosome 4 QTL mapping interval includes several genes involved in the biosynthesis of DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one), a maize defensive metabolite that also is required for callose accumulation in response to aphid feeding. Consistent with the known association of callose with plant defence against aphids, R. maidis reproduction on B73×Mo17 recombinant inbred lines was negatively correlated with both DIMBOA content and callose formation. Further genetic mapping, as well as experiments with near-isogenic lines, confirmed that the Mo17 allele causes increased DIMBOA accumulation relative to the B73 allele. The chromosome 6 aphid resistance QTL functions independently of DIMBOA accumulation and has an effect that is additive to that of the chromosome 4 QTL. Thus, at least two separate defence mechanisms account for the higher level of R. maidis resistance in Mo17 compared with B73.

Changes in life history parameters of Rhopalosiphum maidis (Homoptera: Aphididae) under four different elevated temperature and CO2 combinations.

Biological characteristics of corn leaf aphid, Rhopalosiphum maidis (Fitch), on barley, Hordeum vulgare L., were examined for two generations under four different elevated temperature and CO2 combinations. The developmental duration for each life stage was significantly reduced under the elevated temperature (+4 degrees C). The elevated CO2 (700-750 microl/liter) reduced only the development time of fourth-instar nymph. The overall duration of nymphal stage was reduced in the second generation. Thus, the temperature was the dominant factor to development duration of corn leaf aphid. The fecundity of corn leaf aphid was significantly increased under the elevated temperature and CO2, as well as in the later generation. Elevated temperature and CO2 increased the number of alate production, which may enhance the aphid migration or dispersal and the spread of plant viruses. Corn leaf aphid had the highest intrinsic rate of increase under the elevated temperature and CO2 combination in the second generation. These results indicate that the combined effects of both elevated temperature and CO2 on aphid biology may exacerbate aphid damage on barley under the climate change in accompany with elevated temperature and CO2 level.

First Report of Sugarcane yellow leaf virus Infecting Barley in Tunisia.

Sugarcane yellow leaf virus (ScYLV) causes severe leaf symptoms in sugarcane (Saccharum spp.). It is a single-stranded RNA virus assigned to the genus Polerovirus, family Luteoviridae (1). ScYLV is transmitted by two aphid species, Melanaphis sacchari and Rhopalosiphum maidis. Although barley (Hordeum vulgare), oats (Avena sativa), and wheat (Triticum spp.) are susceptible to ScYLV when experimentally inoculated (3), this virus, related serologically to Barley yellow dwarf virus (BYDV)-RPV (4), has never been detected naturally in these cereals. In this study, 240 barley leaves were randomly collected from six fields in Tunisia following a north-south trend during the high infestation periods (March/April) in the 2013 growing season. Samples were tested by DAS-ELISA, using three antibodies (Bioreba AG, Switzerland), two of them, BYDV-B and BYDV-F, specific to luteoviruses corresponding to BYDV-PAV and BYDV-MAV, respectively, and the third one, BYDV-RPV, specific to the polerovirus synonymous to Cereal yellow dwarf virus (CYDV)-RPV. Based on DAS-ELISA, 30 samples were found positive for B/CYDV infection; 17 out of the 30 infected samples contained a single serotype, BYDV-PAV, and 13 out of the 30 infected samples contained two serotypes, PAV and RPV. Total RNA was extracted from all positive samples, and RT-PCR of the viral CP gene was performed with Lu1/Lu4 primers (2). A product of 531 bp was cloned and sequenced. The identities among the sequences determined varied between 80 to 100%, and from the 17 samples containing BYDV-PAV, six distinct BYDV-PAV sequences were revealed and named PAV-TN1 to PAV-TN6 (GenBank Accession No. JX402453 to JX402457 and KF271792). Fortuitously, all 13 positive samples corresponding to the serotypes PAV-RPV exhibited 98.7 to 99.3% identity with ScYLV isolates. These 13 samples contained three distinct sequences that were named ScYLV-Tun1 to ScYLV-Tun3 (GenBank Accession No. KF836888 to KF836890). Of the 17 PAV-positive samples collected, six were infected with PAV-TN1, four with PAV-TN2, four with PAV-TN3, one with PAV-TN4, one with PAV-TN5, and the last one with PAV-TN6. Of the 13 ScYLV-positive samples, seven were infected with ScYLV-Tun1, four with ScYLV-Tun2, and two with ScYLV-Tun3. Phylogenetic analysis showed that PAV-TN sequences formed a very tight cluster (>98%) corresponding to BYDV subspecies PAV-II, whereas all three Tunisian ScYLV sequences were clustered together. This study provides the first report of ScYLV isolates infecting barley crops in Tunisia, and confirms serological cross-reactivity between ScYLV and BYDV-RPV when commercial antibodies against BYDV-RPV are used.

Direct and indirect effects of warming on aphids, their predators, and ant mutualists.

Species exist within communities of other interacting species, so an exogenous force that directly affects one species can indirectly affect all other members of the community. In the case of climate change, many species may be affected directly and subsequently initiate numerous indirect effects that propagate throughout the community. Therefore, the net effect of climate change on any one species is a function of the direct and indirect effects. We investigated the direct and indirect effects of climate warming on corn leaf aphids, a pest of corn and other grasses, by performing an experimental manipulation of temperature, predators, and two common aphid-tending ants. Although warming had a positive direct effect on aphid population growth rate, warming reduced aphid abundance when ants and predators were present. This occurred because winter ants, which aggressively defend aphids from predators under control temperatures, were less aggressive toward predators and less abundant when temperatures were increased. In contrast, warming increased the abundance of cornfield ants, but they did not protect aphids from predators with the same vigor as winter ants. Thus, warming broke down the ant-aphid mutualism and counterintuitively reduced the abundance of this agricultural pest.

Prey species affects the performance of the aphidophagous ladybird, Coelophora saucia

Performance of ladybird, Coelophora saucia (Mulsant) was studied on seven aphid species in terms of various life attributes. Immature stages developed fastest and survived most on Aphis craccivora. Longevity, fecundity and egg fertility of adults were highest on A. craccivora. Age specific fecundity was triangular in shape with the occurrence of peak oviposition at an early age on A. craccivora and at a later age on Lipaphis erysimi. The net reproductive rate, intrinsic rate of increase, and finite rate of increase of C. saucia were highest on A. craccivora and lowest on L. erysimi. Owing to better performance of C. saucia on A. craccivora, this is considered as the most suitable prey followed by Myzus persicae, Aphis gossypii, Rhopalosiphum maidis, Ceratovacuna silvestrii, Aphis nerii and L. erysimi. It is the first attempt to evaluate prey suitability of this ladybird based on several attributes.

Differential performance and behavior of the corn leaf aphid, Rhopalosiphum maidis, on three species of the biomass crop miscanthus

Miscanthus, a perennial C4-grass, is identified as a promising candidate for biomass production owing to its high yield potential under low nitrogen input and its low susceptibility to diseases and pests. However, some significant insect pests of conventional cereal grain crops such as the corn leaf aphid (Rhopalosiphum maidis) are able to develop on miscanthus. In the prospect of extensive planting of miscanthus for bioenergy, this may lead to the worsening of pest problems in the surrounding conventional crops. The aim of this study was to assess, through laboratory experiments, the ability of R. maidis to colonize three main miscanthus species studied in Europe for biomass production, i.e., Miscanthus×giganteus, M. sacchariflorus, and M. sinensis. In this purpose, comparative analyses of aphid's performance and plant penetration behavior were performed. Despite an altered plant penetration behavior on miscanthus, R. maidis was able to colonize (i.e., to develop and reproduce) the three miscanthus species tested and exhibited a behavior adapted to the transmission of both persistent and non-persistent phytoviruses. M. sacchariflorus and, to a lesser extent, M. sinensis were found less suitable and acceptable host plant for R. maidis than M.×giganteus. Results are discussed in terms of agronomic risks and implications for miscanthus improvement programs.

Molecular characterization of aphids infesting sorghum in China

Sorghum aphid (Melanaphis sacchari), greenbug (Schizaphis graminum) and corn leaf aphid (Rhopalosiphum maidis) are the main pests of sorghum in China. Genotype characterization and/or biotype identification of pests is the first step for cereal breeding programme to obtain resistant cultivars. DNA barcoding technique provides an effective tool for species and biotype diagnosis in various organism. In this study, we sequenced a fragment of 680 bp of cytochromecoxidase I (COI) gene from above aphid species collected from 16 sorghum growing regions in China. The results revealed that (i) No polymorphism was found in the mitochondrial DNA from different sorghum aphid and greenbug populations. The diversity in these two species was not as much as we expected, (ii) Three haplotypes were identified in corn leaf aphid clones. The most common haplotype was the same as that in Canada, USA and UK and (iii) Mitochondrial COI sequences could effectively distinguish different aphid species, and further different haplotypes within an aphid species.

Effect of some insecticides in reducing the population of two aphid species, Rhopalosiphum maidis and Schizaphis graminum on sorghum varieties, Horus and Dorado.

Effect of some insecticides in reducing the population of two aphid species, Rhopalosiphum maidis and Schizaphis graminum on sorghum varieties, Horus and Dorado.