Showing papers on "Aphididae published in 2000"
TL;DR: Alate production in pea aphids was significantly increased in large populations of two PASS‐ and PAR‐positive subclones relative to their parent clones, and this ameliorative effect of facultative bacteria at 25 °C was not found for two other sets of parent clones and their derived sub clones.
Abstract: The effects of two bacterial endosymbionts, designated PASS and PAR, were evaluated on the pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera:Aphididae), in which they occur facultatively, and on the blue alfalfa aphid, A. kondoi Shinji, in which these bacteria have not been found in natural populations. Subclones of pea aphids and blue alfalfa aphids, derived from parent aphid clones that did not contain PASS or PAR, were infected with one or both bacteria, generating PASS- and/or PAR-positive subclones with minimal genetic differences from the parent clones. Under laboratory conditions at 20 °C, PAR consistently reduced the fecundity (by between 19 and 60%) of subclones derived from three different parent pea aphid clones on bur clover, Medicago hispida Gaertn. PAR had intermediate effects on pea aphids reared on sweet pea, Lathyrus odoratus L., and had no significant effect on pea aphids on alfalfa, Medicago sativa L. The effect of PASS was either neutral or negative, depending on parent clone as well as host plant. Also at 20 °C, PASS reduced fecundity (70–77%) and longevity (40–48%), and increased the age of first reproduction (by up to 1.5 days) of blue alfalfa aphid reared on alfalfa and clover. PAR had a less dramatic effect (e.g., 30–39% reduction in fecundity) on these traits of blue alfalfa aphid. In contrast, PAR and PASS increased the fitness of pea aphid subclones of one parent clone reared for three generations at 25 °C on each of the three test plants. Without facultative bacteria, fecundity of the parent clone was reduced to a mean total of 35. However, this ameliorative effect of facultative bacteria at 25 °C was not found for two other sets of parent clones and their derived subclones. Alate production in pea aphids was significantly increased in large populations of two PASS- and PAR-positive subclones relative to their parent clones. Attempts to transmit PASS or PAR horizontally, i.e., from aphid to aphid via feeding on host plants (bur clover), were unsuccessful.
278 citations
TL;DR: It is concluded that intraguild interactions have a primary effect in driving fluctuations in aphid parasitoid populations and can substantially alter the effectiveness of aphid Parasitoids as biological‐control agents.
Abstract: We reviewed the literature on aphid parasitoids to determine the occurrence, nature and outcome of intraguild interactions. Intraguild interactions were described for larval, pupal and adult aphid parasitoids and by the type of natural enemy (fungus, predator, or parasitoid). They appear to be prevalent in most aphid parasitoid systems and, except for parasitoid-parasitoid interactions, they are mostly asymmetric, with aphidophagous predators and pathogens killing parasitoids. The limited experimental evidence from field studies is insufficient to provide a comprehensive pattern of the consequences of intraguild interactions for aphid parasitoid populations in general and, more specifically, for the efficacy of biological control. However, because intraguild interactions are widespread in aphid-natural enemy communities and mostly detrimental to aphid parasitoids, we conclude that intraguild interactions have a primary effect in driving fluctuations in aphid parasitoid populations. Drawing on case studies, we further argue that intraguild interactions can substantially alter the effectiveness of aphid parasitoids as biological-control agents.
225 citations
TL;DR: The causal agent, Sugarcane yellow leaf virus (ScYLV), is a Polerovirus of the Luteoviridae family and was transmitted by the sugarcane aphid, Melanaphis sacchari, and also by the corn leaf aphids, Rhopalosiphum maidis, and the rice root aphid.
Abstract: Sugarcane, Saccharum spp hybrid, is widely infected in the United States and many other countries with a yellowing and stunting disease called sugarcane yellow leaf syndrome The causal agent, Sugarcane yellow leaf virus (ScYLV), is a Polerovirus of the Luteoviridae family In this study, it was transmitted by the sugarcane aphid, Melanaphis sacchari, and also by the corn leaf aphid, Rhopalosiphum maidis, and the rice root aphid, R rufiabdominalis Two other aphids that infest sugarcane in Hawaii did not transmit the virus Some Hawaiian sugarcane cultivars are susceptible to ScYLV, while others remain virus-free in the field The latter were not infected when inoculated with viruliferous M sacchari Virus-free plants of susceptible cultivars were produced through apical meristem culture and were readily reinfected by viruliferous M sacchari They were also quickly reinfected when planted in a field in proximity to other infected sugarcane naturally infested with M sacchari Sugarcane cultivars are hybrids of several Saccharum species In a field-grown collection of Saccharum and related species, 11 to 71% of the clones of four of the species were infected with ScYLV None of the related genus Erianthus plants were infected, but four clones were infected experimentally by aphid inoculation A low to moderate percentage of corn, rice, and sorghum seedlings became infected when inoculated with ScYLV, but barley, oats, and wheat proved to be very susceptible None of seven weeds common in sugarcane fields were infected with ScYLV
150 citations
TL;DR: It is hypothesized that ant-attended aphids are under intense selective pressures that act against aphid clones which fail to attract many ants, so that aphids have developed an adaptive mechanism to allocate a larger fraction of resources to the honeydew when they are requested to do so by the ants in order to ensure the ants' consistent visitation.
Abstract: The defensive effects of ants against aphid predators have been well documented in the mutualistic relationship of aphids and their attending ants. However, it is not clear whether ant attendance has any direct effect on the aphids' growth and reproduction. Through field experiments, this study evaluates the benefits and, in particular, the costs of ant attendance to aphid colonies, focusing on the drepanosiphid aphid Tuberculatus quercicola which is associated with the Daimyo oak, Quercus dentata, and which is always attended by the red wood ant Formica yessensis. Ant attendance was clearly beneficial to the aphid; the exclusion of ants led to a significant increase in the extinction rate of aphid colonies. However, MANOVA and randomized block ANOVA indicated that in colonies continuously attended by ants, aphids had significantly smaller body size and produced a smaller number of embryos than in colonies isolated from ants when they were reared under homogeneous host conditions free from natural enemies. Thus, ant attendance had a negative influence on the growth and reproduction of the aphids, even though it contributed to the greater longevity of the aphid colonies. We hypothesize that ant-attended aphids are under intense selective pressures that act against aphid clones which fail to attract many ants, so that aphids have developed an adaptive mechanism to allocate a larger fraction of resources to the honeydew when they are requested to do so by the ants in order to ensure the ants' consistent visitation.
122 citations
TL;DR: Effects of nitrogen deficiency in hydroponically grown barley seedlings on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated.
Abstract: Effects of nitrogen deficiency in hydroponically grown barley seedlings (Hordeum vulgare L.) on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated. Plant growth was significantly reduced in seedlings grown without nitrogen. Aphid intrinsic rate of increase (r m ) was also significantly lower on these plants compared with that on plants grown with 8 mol m -3 nitrogen. Phloem sap was collected from seedling stems by aphid stylectomy and amino acids quantified by HPLC. There was a significant reduction in the concentration of non-essential amino acids as a group, but not of essential amino acids. Electrical penetration graphs (EPG) indicated that aphids reached the phloem more quickly and fed for longer on plants grown with nitrogen. This is the first reported study in which this combination of techniques has been used to understand the interactions of an aphid and plant under different environmental conditions.
112 citations
TL;DR: The data suggest that stimulation of reproduction by these insecticides probably does not play a major role in cotton aphid outbreaks or resurgence, and that modifying aphid population structure and growth through the use of juvenoids such as pyriproxifen may be an effective proactive approach to pest control without adversely impacting beneficial organisms or causing pest resurgence.
Abstract: Insecticides are often implicated in causing outbreaks of the cotton aphid, Aphis gossypii (Glover) (Homoptera: Aphididae), through stimulation of reproduction. In this study we report the sublethal effects of dosages of bifenthrin, acephate, carbofuran or pyriproxifen on cotton aphid reproduction. We could not detect any increase or decrease in the intrinsic rate of increase of cotton aphids exposed to bifenthrin, acephate or carbofuran. However, we did detect some increases in the net reproductive rate of aphids treated with bifenthrin justifying further investigation of the effect on reproduction by this insecticide. Trends based on simple linear regression models suggest that sublethal dosages of bifenthrin or carbofuran have a negative impact on aphid population growth as dosages increase. These data suggest that stimulation of reproduction by these insecticides probably does not play a major role in cotton aphid outbreaks or resurgence. Pyriproxyfen is a juvenoid currently used for control of whiteflies in cotton. It demonstrated significant activity towards cotton aphid reared on treated cotton in our bioassays. Pyriproxyfen caused sterility in most aphids exposed to dosages exceeding 1 ppm, and reduced aphid longevity by approximately 50%. However, it did not appear to greatly influence the reproductive potential or longevity of reproductively mature aphids. A field study indicates that pyriproxyfen affects cotton aphid population structure and may have potential in managing cotton aphid outbreaks. Modifying aphid population structure and growth through the use of juvenoids such as pyriproxifen may prove to be an effective proactive approach to pest control without adversely impacting beneficial organisms or causing pest resurgence.
78 citations
TL;DR: Olfactometry showed that the response of spring migrants of the bird cherry‐oat aphid, Rhopalosiphum padi (L.) (Homoptera: Aphididae), to the repellent winter host volatile methyl salicylate changes with age of the adult aphid.
Abstract: Olfactometry showed that the response of spring migrants of the bird cherry-oat aphid, Rhopalosiphum padi (L.) (Homoptera: Aphididae), to the repellent winter host volatile methyl salicylate changes with age of the adult aphid. Between three and four days after becoming adult, and having left the winter host Prunus padus L., aphids lost their negative response to the chemical. The change in response was not associated with contact with a summer host, oats. In a settling choice bioassay, migrants avoided oats which had been exposed to volatile methyl salicylate. Aphids with removed antennal tips did not avoid the exposed plant, indicating that plant choice was influenced by cues from the plant surface. The results are discussed in relation to the use of methyl salicylate in integrated control.
70 citations
TL;DR: Reduced waxbloom in peas is associated with lower natural infestations of an aphid, but also with increased susceptibility to a folivorous beetle.
Abstract: Seven accessions or varieties of cultivated pea Pisum sativum L. varying in surface waxbloom characteristics were grown in replicated small plots (1 m2) for two seasons to monitor natural infestations of insect herbivores and abundance of predatory insects. Waxbloom was quantified on the basis of the amount of waxes extractable from leaf surfaces, densities of wax crystals visible with scanning electron microscopy, and visual appearance. During each season, pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphidae), densities per plant were significantly lower on peas with reduced surface waxbloom as compared with peas with standard or ‘normal’ surface waxbloom. This difference was greatest between two near-isolines of peas differing in expression of a mutation that reduces surface waxes. Although reduced-waxbloom plants had lower end-of-season above ground biomass and vine lengths, including these variables as covariates did not affect the significance of the waxbloom effects on aphid densities. Damage to leaves and stipules by the pea leaf weevil Sitona lineatus (L.) (Coleoptera: Curculionidae) was greater on reduced-waxbloom peas than normal-waxbloom peas. Thus, as occurs in other crops, reduced waxbloom in peas is associated with lower natural infestations of an aphid, but also with increased susceptibility to a folivorous beetle. Populations of predatory coccinellids did not differ consistently between years on reduced-waxbloom versus normal-waxbloom peas, failing to support a hypothesis that predator populations are higher on reduced waxbloom peas, contributing to the lower aphid populations on these plants.
65 citations
TL;DR: It is concluded that avoidance of coccinellids by L. fabarum contributes to the negative association between the abundance of coc cinellid and parasitoids in the field.
Abstract: An experimental plot of the aphid Aphis fabae on various host plant species was colonized by natural populations of the aphidiine parasitoid Lysiphlebus fabarum and insect predators, especially coccinellids. Parasitism of A. fabae by L. fabarum was significantly depressed on plants bearing coccinellids. The number of parasitized aphids increased with aphid abundance on three plant species (Papaver dubium, Rumex obtusifolius, Vicia faba), but not on the plant species (Chenopodium album) which bore very high numbers of coccinellids. In complementary laboratory experiments, L. fabarum offered a choice between odours of plants infested with A. fabae and/or coccinellids selected the odour fields from coccinellid treatments at significantly lower frequency than the odour fields of other treatments. It is concluded that avoidance of coccinellids by L. fabarum contributes to the negative association between the abundance of coccinellids and parasitoids in the field.
64 citations
TL;DR: Aphid infestation induces PR-proteins differently in barley susceptible or resistant to the birdcherry-oat aphid (Rhopalosiphum padi).
Abstract: Aphid infestation induces PR-proteins differently in barley susceptible or resistant to the birdcherry-oat aphid (Rhopalosiphum padi)
61 citations
TL;DR: In this paper, the potential of using Vertalec, BioNeem, and Safer's soap for the control of lettuce aphids is discussed in relation to aphid species and crop management.
Abstract: The objective of our research was to identify alternatives to synthetic pesticide treatments to prevent aphid outbreaks in greenhouse lettuce crops. In the laboratory, we determined the susceptibility of three lettuce-infesting aphid species, Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Nasonovia ribisnigri (Mosley), to the hyphomycete Verticillium lecanii (Viegas) (strain Vertalec), the plant triterpenoid molecule azadirachtin (BioNeem), and an insecticidal soap (Safer’s). Estimated LC50 and LT50 obtained in the laboratory indicated that the three aphid species were susceptible to the entomopathogenic fungus, the plant extract, and the soap. Under greenhouse conditions, we assessed the potential of the three pesticides to reduce aphid populations and compared it with that of a synthetic insecticide, the organophosphate Malathion. Greenhouse experiments demonstrated that all three pesticides significantly reduced the population of each aphid species compared with the untreated plants. This study also revealed differences in aphid susceptibility between aphid species and between laboratory bioassays and greenhouse trials. The high initial aphid densities, difficulties to reach the aphids on the undersurface of leaves, stains left by Vertalec on the harvested lettuce, and high cosmetic standards for lettuce mitigated the performance of the insecticides. The potential of using Vertalec, BioNeem, and Safer’s soap for the control of lettuce aphids is discussed in relation to aphid species and crop management.
TL;DR: Although there were no changes in fecundity caused by plant morphology, longevity was significantly influenced both by leaf type and stipule size.
Abstract: Plant morphology has been shown to influence the biology of herbivores through changes in oviposition behavior, feeding preferences, and plant tenure times. The goal of the work herein was to establish whether or not differences in plant morphology can affect the performance and distribution of the pea aphid, Acyrthosiphon pisum (Harris), on peas, Pisum sativum L. Fecundity and intrinsic rate of increase were the selected parameters to measure the aphid's performance. Genetic near-isolines of the garden pea were used to determine the effect of plant morphology on the pea aphid. The use of genetic near-isolines eliminates as much as possible confounding effects, such as phytochemicals, that could occur when comparing different plant species or cultivars. Four plant lines differing in leaf morphology (Normal, af, tl, and aftl) and two lines with normal and reduced stipules (Normal and st) were tested. Changes in plant morphology did not have a significant effect on pea aphid total fecundity or intrinsic rate of increase. Although there were no changes in fecundity caused by plant morphology, longevity was significantly influenced both by leaf type and stipule size. The morphology of the leaf did not affect the within-plant distribution of the pea aphid on three plant lines tested.
TL;DR: It is hypothesized that competition among sympatric sugar sources including rival aphids and extrafloral nectaries is a factor restricting aphids to be myrmecophilous.
Abstract: Among plants and herbivores, two types of conflicts occur in relation to mutualism with ants: one is competition for ant mutualism among myrmecophilous herbivores and plants, and the other is the conflict whether to attract or repel ants between myrmecophiles and nonmyrmecophiles that are damaged by ants. We investigated the extent to which two species of aphids (Megoura crassicauda and Aphis craccivora) and extrafloral nectaries on their host plant (Vicia faba var. minor) interact with one another for their relationships with ants. We designed an experiment where ants can choose to visit seedlings colonized by (1) M. crassicauda, (2) A. cracivora, (3) both aphid species, or (4) neither aphid species. Ants preferred A. craccivora to extrafloral nectaries and avoided tending M. crassicauda. We also analyzed the population growth of each aphid when it coexists with (1) ants, (2) the other aphid species, (3) ants and the other aphid species, or (4) neither of them. Under ant-free conditions, we detected an exploitative competition between the two aphid species. The ants had no significant effect on the population of A. craccivora, whereas they had negative effects on the population growth of M. crassicauda by attacking some individuals. When both aphids coexisted, M. crassicauda suffered ant attack more intensely because A. craccivora attracted more ants than extrafloral nectaries despite ant-repelling by M. crassicauda. On the other hand, the ants benefited A. craccivora by eliminating its competitor. To avoid ant attack, aphids may have been selected either to be more attractive to ants than other sympatric sugar sources or to repel the ants attracted to them. We hypothesize that competition among sympatric sugar sources including rival aphids and extrafloral nectaries is a factor restricting aphids to be myrmecophilous.
TL;DR: A study of aphids and aphidophagous coccinellids on Scots pine, finding coexistence with ants appears to be associated with either an intolerance of low aphid densities, in Coccinella septempunctata and Harmonia quadripunctata, or with extreme dietary specialisation, in Myzia oblongoguttata.
Abstract: It is generally believed that most homopteran-eating insects avoid ant-tended colonies of Homoptera, due to the ant aggression they encounter there. However, because homopteran colonies which are ant-tended often persist for longer than untended colonies, some homopteran-eaters may utilise ant-tended Homoptera when untended colonies are scarce. Furthermore, a few homopteran-eaters are myrmecophilous, habitually coexisting with ants. To investigate these phenomena, a study was made of aphids and aphidophagous coccinellids (ladybirds) on Scots pine, Pinus sylvestris, growing in areas foraged and unforaged by the wood ant Formica rufa. The non-tended aphid Schizolachnus pineti exhibited a marked population decline in late summer but persisted in both areas at very low density. Facultatively tended Cinara aphids exhibited higher population densities when associated with F. rufa, and remaining colonies of these aphids were only found associated with ants in late summer. Coccinellids exhibited considerable interspecific variability in their level of association with F. rufa, and there was some evidence of an increase in certain species’ frequencies of occurrence with the ant when Cinara aphids were all ant-tended, in late summer. Coexistence with ants appears to be associated with either an intolerance of low aphid densities, in Coccinella septempunctata and Harmonia quadripunctata, or with extreme dietary specialisation, in Myzia oblongoguttata. Similar factors to those which bring C. septempunctata into contact with ants were probably of importance in the initial stages of the evolution of myrmecophily of its congener, Coccinella magnifica.
TL;DR: R was significantly greater in exclusion patches than supplemented and natural patches, indicating that coccinellids markedly reduced aphid numbers in patches even when aphid density was extremely high.
Abstract: The objectives of this study were to determine if coccinellids adjusted their distribution within spring wheat fields in response to spatial variation cereal aphid density in the fields and to describe the patterns of cereal aphid population growth that resulted. Field experiments were completed in which the physical dimensions of patches infested with cereal aphids, cereal aphid density, and access to patches by coccinellids were varied. Aphid infestations consisted of naturally occurring densities (natural patches) and much greater densities created by supplementing patches with aphids (supplemented patches). Coccinellids were denied access to some supplemented patches (exclusion patches) but allowed unlimited access to others. Densities of adult Hippodamia convergens and Coccinella septempunctata were correlated with aphid density in patches whereas density of Coleomegilla maculata was not. Aggregation by coccinellids was independent of patch area. The realized aphid population growth rate (r) was lower in supplemented than natural patches in all four trials but was significantly lower in only one trial. The lower r in supplemented patches was not exclusively caused by coccinellid predation, and emigration of aphids from patches probably also contributed. r was significantly greater in exclusion patches than supplemented and natural patches, indicating that coccinellids markedly reduced aphid numbers in patches even when aphid density was extremely high.
TL;DR: Five species of entomopathogenic fungi were recorded including four entomophthorales and the hyphomycete, Beauveria bassiana, which was the most prevalent species within populations of M. dirhodum and Pandora neoaphidis, and a high level of susceptibility to P.noxia was indicated.
Abstract: Surveys were conducted in the summer andwinter rainfall wheat producing regions of SouthAfrica in a first attempt to investigate theidentity and impact of entomopathogenic fungi withinthe cereal aphid complex. Wheat produced underdryland and irrigated conditions was surveyed duringthe 1996 and 1997 seasons. Six cereal aphid specieswere recorded of which the Russian wheat aphid, Diuraphis noxia, was the most abundantunder dryland conditions in the summer rainfallregion as opposed to the oat aphid, Rhopalosiphum padi, in the winter rainfallregion. Rose grain aphid, Metopolophiumdirhodum, was most prevalent underirrigated conditions in the summer rainfall region.Five species of entomopathogenic fungi were recordedincluding four entomophthorales and the hyphomycete,Beauveria bassiana. TheEntomophthorales included Pandora neoaphidis, Conidiobolus obscurus, C.thromboides, and Entomophthoraplanchoniana. Pandora neoaphidis wasthe most important etiological agent recorded fromD. noxia, with up to 50% mycosis recordedunder dryland conditions in the Bethlehem summerrainfall region. Similarly, P. neoaphidis wasthe most prevalent species within populations ofM. dirhodum. under irrigated conditions in theBergville/Winterton summer rainfall region (up to77% mycosis). However, mycoses of R. padi didnot exceed 1.7% in samples from these areas,suggesting that R. padi may be lesssusceptible to P. neoaphidis than M.dirhodum. Epizootics in populations of D.noxia under dryland conditions in both the winterand summer rainfall regions indicated a high levelof susceptibility to P. neoaphidis.Occurrences of hymenopterous parasitoids andpredators in populations of D. noxia were low,although a parasitism level of 25% was recorded inone small sample of R. padi collected from anirrigated field in the summer rainfall region.
TL;DR: Evaluating the impact of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), on the cereal aphid complex in wheat found there was no interaction between D. noxia resistance and the population density of the other aphid species observed.
Abstract: Field experiments were conducted in 1997 and 1998 to evaluate the impact of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), on the cereal aphid complex in wheat. Two spring wheats were planted: the variety “Centennial” (Russian wheat aphid susceptible) and the advanced line IDO488 (Russian wheat aphid resistant). IDO488 incorporates the resistance found in PI 294994 into a Centennial background. Field plots were artificially infested with adult D. noxia and sampled weekly. The most abundant aphid species in 1997 were Metopolophium dirhodum (Walker), Sitobion avenae (F.), D. noxia, and Rhopalosiphum padi (L.). In 1998, the order of abundance was M. dirhodum, R. padi, S. avenae, and D. noxia. The resistant genotype had significantly fewer D. noxia than the susceptible one during both years. However, plant genotype had no significant effect on the other aphid species in either year. Both the initial density of D. noxia and plant growth stage, had a significant effect on D. noxia population development, but had no effect on the other aphid species. There was no interaction between D. noxia resistance and the population density of the other aphid species observed.
01 Jan 2000
TL;DR: In greenhouse experiments, the likelihood of competition between R. padi and S. avenae on wheat seedlings and tillering plants was evaluated and the presence of either aphid species negatively affected the reproductive rate of the other.
Abstract: The cereal aphids Rhopalosiphum padi L. and Sitobion avenae (F.) coexist on the same host plant but occupy different ecological niches. R. padi arrives first in the season and reaches its population peak before S. avenae. In addition, R. padi prefers the stem and lower leaves, whereas S. avenae is found mostly on the ears and upper leaves of the plant. In greenhouse experiments, the likelihood of competition between R. padi and S. avenae on wheat seedlings and tillering plants was evaluated. The reproductive rate of S. avenae on tillering plants was negatively affected by previous infestation by R. padi, and this effect was larger when R. padi infestation started at an earlier plant growth stage. Likewise, previous infestation by R. padi decreased S. avenae reproduction on seed- lings. In contrast, previous infestation by S. avenae on the flag leaf of flowering plants did not affect R. padi on that plant part. When both aphid species co-occurred from the beginning, the presence of either aphid species negatively affected the reproductive rate of the other. R. padi consistently had a higher rate of population increase than S. avenae. The presence of the other aphid species did not affect within-plant aphid distribution or alate aphid production. Results were similar on wheat seedlings and tillering plants. Finally, alate S. avenae preferred uninfested seedlings over R. padi- infested ones, whereas no preference was observed when the experiment was performed with tillering plants.
Journal Article•
TL;DR: The severe aphid outbreak during the 1995 cotton growing season served as a focal point to bring the industry together to discuss the status of cotton integrated pest management and to plan future directions, including increased awareness, greater understanding of cotton aphid biology and improved pest management decisions.
Abstract: During the 1990s, the cotton aphid (Aphis gossypii Glover) escalated from an occasional pest to an annual, severe pest of San Joaquin Valley (SJV) cotton. Although the cotton aphid is not a new insect in the SJV, the change in the bionomics of this pest dictated that new research efforts be directed toward its biology, damage thresholds and management. The 1980s saw major shifts in agronomic practices. For example, the introduction of a plant growth regulator allowed growers to promote vigorous plant growth, rather than limiting growth and yield potential through the practice of water and nitrogen stress. Recent field research has shown that applying high rates of nitrogen to cotton plants increases cotton aphid reproductive rates and can create conditions favorable to aphid outbreaks. The new practice of promoting vigorous growth may have created an optimal host plant environment for cotton aphid reproduction and survival. In addition, the shift to using pyrethroids to control other arthropod pests has enhanced the buildup of cotton aphid populations. The severe aphid outbreak during the 1995 cotton growing season served as a focal point to bring the industry together to discuss the status of cotton integrated pest management and to plan future directions. Results of this effort include increased awareness, greater understanding of cotton aphid biology and improved pest management decisions.
TL;DR: Host selection, development, survival, and reproduction of the turnip aphid, Lipaphis erysimi, on selected green and red cabbage varieties, were studied in the laboratory and factors that might affect aphid host selection, growth, longevity, fecundity, and survivorship were discussed.
Abstract: Host selection, development, survival, and reproduction of the turnip aphid, Lipaphis erysimi (Kaltenbach), on selected green and red cabbage varieties, Brassicae oleracea L. variety capitata, were studied in the laboratory. Although numbers of alate L. erysimi on different varieties varied generally, more alate adults and nymphs were observed on green than on red varieties on day 3; whereas, these differences were not so significant on day 15. There were no significant differences in alate adults on all six varieties on day 15. Numbers of nymphs and apterous adults of L. erysimi varied among the varieties. When mean numbers of those aphids on green varieties were compared with those on red varieties, the green varieties had more nymphs and apterous adults than those on the red varieties. Developmental durations of L. erysimi nymphs also varied among all varieties, and the nymphs fed on green varieties developed longer than those fed on red varieties. Adult longevities on these cabbage varieties were not significantly different; whereas, the adult fecundities were. Survival rates of L. erysimi varied greatly among all varieties, but there are no significant differences between the green and red varieties. Factors that might affect aphid host selection, growth, longevity, fecundity, and survivorship were discussed.
TL;DR: Results add to a growing body of evidence suggesting M. nicotianae and M. persicae are conspecific, and with the exception of their responses to a choice between lettuce and collards, the host preference behavior of a green peach aphid population, a red tobacco aphidpopulation, and a green tobacco Aphid population was indistinguishable in host preference experiments.
Abstract: Prior to designation as distinct species, an appellation presently in question, the tobacco aphid, Myzus nicotianae Blackman (Homoptera: Aphididae), was classified as a tobacco-feeding form of the green peach aphid, Myzus persicae (Sulzer). In this study, RAPD polymorphisms distinguished members of the Myzus persicae complex (M. persicae and M. nicotianae) from three outgroup Myzus species (M. cerasi (F.), M. hemerocallis Takahashi, and M. varians Davidson). Polymorphisms within the complex did not separate populations on the basis of host association (tobacco versus other host plants) or geographic origin (collections from the United States, Europe, and Japan). Similarly, while GC-MS analysis of cuticular hydrocarbon profiles revealed both developmental and inter-populational differences within the M. persicae complex, it did not separate populations of tobacco feeding aphids from those collected off non-tobacco hosts. Finally, with the exception of their responses to a choice between lettuce and collards, the host preference behavior of a green peach aphid population, a red tobacco aphid population, and a green tobacco aphid population was indistinguishable in host preference experiments. These results add to a growing body of evidence suggesting M. nicotianae and M. persicae are conspecific.
TL;DR: Direct current electrical penetration graphs (DC-EPGs) were used to analyze the stylet penetration activities of cowpea aphid, Aphis craccivora Koch, on plants of aphid-resistant (ICV-12) and Aphid-susceptible ( ICV-1) cultivars ofcowpea, Vigna unguiculata (L.) Walpers.
Abstract: Direct current electrical penetration graphs (DC-EPGs) were used to analyze the stylet penetration activities of cowpea aphid, Aphis craccivora Koch, on plants of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpea, Vigna unguiculata (L.) Walpers. Aphid stylet penetration on whole plants at seedling, flowering, and podding stages were studied in one experiment, and in another experiment excised leaves from seedling plants, excised flowers, and excised pods were tested. Electrical signals depicting the aphid stylet penetration activities on their host plants were amplified, recorded onto a paper chart recorder, and scored for specific waveform patterns. Compared with similar tissues of ICV-1, intact leaves and excised seedling foliage of ICV-12 plants caused severe disruption of aphid stylet penetration activities. This was manifested in frequent penetration attempts that were abruptly terminated or unsustained, and in shorter penetration times, signifying antixenosis resistance in ICV-12. There was reduced occurrence of E waveforms, which represent stylet activity in plant vascular tissues. Also, prior exposure of test aphids to plants of one cultivar did not significantly influence the expected stylet penetration activities on plants of the other cultivar. Overall, ICV-12 exhibited high levels of resistance against A. craccivora.
TL;DR: Evaluated the nutritional interactions among alfalfa, Medicago sativa L. ‘OKO8’, and faba bean, host plants, pea aphid herbivores, Acyrthosiphon pisum (Harris), and a lacewing predator, Chrysoperla rufilabris Burmeister to suggest qualitative differences in the nutritional value ofpea aphids between host plants.
Abstract: The importance of host plant effects on aphids, and their natural enemies, has been well documented. However, few studies have isolated the mechanisms that determine suitability of insect prey among host plants for the survival and development of predators. We evaluated the nutritional interactions among alfalfa, Medicago sativa L. ‘OKO8’, and faba bean, Vicia faba L. ‘Windsor’, host plants, pea aphid herbivores, Acyrthosiphon pisum (Harris), and a lacewing predator, Chrysoperla rufilabris Burmeister. The survival and development of lacewing larvae supplied with five daily levels (1.2–16.4 mg) of pea aphids reared on either alfalfa or faba bean were documented. Compared with aphids reared on faba bean, those reared on alfalfa stored 6.3 times greater levels of myristic acid resulting in a 2.7-fold increase in total fatty acid content (micrograms per milligram of aphid weight). This increase in total fatty acids equated to an ≈1.3-fold increase in available calories for C. rufilabris provided with...
TL;DR: From exhaustive counting of infested leaves and quantitative measurement of stickiness with a thermodetector, a positive relationship can be established between the seriousness of fibre stickiness and aphid outbreaks at the end of the season.
Abstract: 'Sticky cotton' causes substantial economic loss in central Africa. The phenomenon is the result of honeydew excreted by sapsucking insects, mainly the aphid Aphis gossypii Glover. The chemical protection currently available to farmers does not limit this type of damage effectively. From exhaustive counting of infested leaves and quantitative measurement of stickiness with a thermodetector, a positive relationship can be established between the seriousness of fibre stickiness and aphid outbreaks at the end of the season. A control method involving the topping of plants after boll opening reduces the number of leaves on which aphids feed and thus the abundance of the aphids.
TL;DR: The results suggest that Australian cotton aphid was resistant to endosulfan and pyrethroids but not to carbamates or organophosphates, in contrast to overseas studies.
Abstract: Cotton aphids, Aphis gossypii, may be more troublesome in transgenic (Ingard®) cotton, because an overall reduction in pesticide use in transgenic cotton for the control of pests such as Helicoverpa spp., gives reduced control of concurrent aphids. Additionally, coincidental cotton aphid in conventional cotton is being exposed to an increasing number of organophosphate insecticides targeted against Helicoverpa spp. Resultant insecticide sprays targeted specifically at cotton aphid, are likely to increase and must be managed to maintain insecticide susceptibility. As a first step to studying resistance in cotton aphid, two strains were collected from unsprayed sources and tested against 21 registered or experimental insecticides by laboratory bioassay, to establish baseline data for resistance monitoring. The LC99.9 of the more susceptible strain was used arbitrarily as a discriminating concentration to detect resistance in three populations of cotton aphid collected in cotton growing districts of New South Wales. In contrast to overseas studies, our results suggest that Australian cotton aphid was resistant to endosulfan and pyrethroids but not to carbamates or organophosphates.
TL;DR: It is suggested that the salivary enzyme difference between the 2 aphid species (i.e., catalase and peroxidase) is important in the type of damage symptom formation on susceptible wheat plants.
Abstract: Four hydrolases and five oxido-reductases were examined using native stacking polyacrylamide gel electrophoresis. Homogenate of Russian wheat aphid, Diuraphis noxia (Mordvilko), bird cherry-oat aphid, Rhopalosiphum padi (L.), ‘Arapahoe’ (aphid-susceptible) and ‘Halt’ (aphid-resistant) wheat, Triticum aestivum L., and powdery mildew–infected Erysiphe graminis DC. ex Merat f. sp. tritici Em. Marchal, Arapahoe wheat leaves were assayed for enzyme activities. Pectinesterase, polygalacturonase (or pectinase), cellulase, and amylase activities were examined in the hydrolase group. Catalase, peroxidase, catechol oxidase, superoxide dismutase, and ascorbate oxidase activities were examined in the group of oxido-reductases. The two aphid species had the same hydrolases but different oxido-reductases. Although pectinesterase and cellulase enzymes were present in D. noxia and R. padi, the banding patterns were different. Polygalacturonase and δ-amylase were not detected from either aphid species. In the oxi...
Journal Article•
TL;DR: The results suggest, on the one hand, that being tended by ants increases the likelihood that an aphid species will evolve an association with host plants that produce EFNs, or on the otherhand, that aphidspecies associated with host plant species carrying EFNs were more likely than other species to evolve a association with ants.
Abstract: The evolution of extrafloral nectaries (EFN) and the evolution of ant-aphid associations may have influenced each other. Published records allowed me to determine whether aphid species are associated with ants and whether they are associated with host plant species with EFNs. On the basis of these results a comparative phylogenetic study was conducted on a subgroup of monoeocious aphid species living above the soil surface. As aphid phylogeny was unresolved below the family level, I analysed two families – Aphididae and Drepanosiphidae – separately. Within each family, a large number of random phylogenies were generated and each random tree was analysed with a standard phylogenetic approach. The results suggest, on the one hand, that being tended by ants increases the likelihood that an aphid species will evolve an association with host plants that produce EFNs, or on the other hand, that aphid species associated with host plants carrying EFNs were more likely than other species to evolve an association with ants. I present two new hypotheses – the host-selection hypothesis and the host-sharing hypothesis – to explain these evolutionary patterns. The hypothesis that ant-attended homopterans may function as EFNs is rejected by the evolutionary patterns found in this study.
TL;DR: In field trials in Korea, employing traps releasing the two compounds in differing ratios, the most effective sex pheromone blend for trapping male T. momonis was found to be 85 : 15 nepetalactone–nepetalactol.
Abstract: Chemical analysis of the volatiles released by sexual females (oviparae) of the peach aphid, Tuberocephalus momonis, identified two ubiquitous aphid sex pheromone components, (4aS,7S,7aR)-nepetalactone and (4aS,7S,7aR)-nepetalactol, in a ratio of 4 : 1. In field trials in Korea, employing traps releasing the two compounds in differing ratios, the most effective sex pheromone blend for trapping male T. momonis was found to be 85 : 15 nepetalactone–nepetalactol. Surprisingly, large numbers of presexual females (gynoparae) of this species were also collected when the catching rates were highest. In addition to T. momonis, over 20 other species of aphids were caught, particularly Myzus lythri, M. dycei, Lachnus tropicalis and M. persicae, in descending order of abundance.