Showing papers on "Aphididae published in 2005"

Aphid Protected from Pathogen by Endosymbiont

Abstract: Aphids are associated with several facultative bacterial endosymbionts that may influence their interactions with other organisms We show here that one of the three most common facultative symbionts of pea aphid (Acyrthosiphon pisum), the bacterium Regiella insecticola, has a major effect on host resistance to a fungal pathogen Experimental establishment of the bacterium in uninfected aphid clones led to higher survival after fungal attack The bacteria also increased the aphid's inclusive fitness, because the presence of the symbiont reduced the probability of fungal sporulation on aphid cadavers, hence lowering the rate of transmission of the disease to nearby related aphids

Response of economically important aphids to components of Hemizygia petiolata essential oil

Abstract: The essential oil of Hemizygia petiolata Ashby (Lamiaceae) contains high levels (> 70%) of the sesquiterpene (E)-beta-farnesene, the alarm pheromone for many economically important aphid species. In order to test the suitability of H. petiolata oil as a source of (E)-beta-farnesene for use in new integrated aphid control strategies, behavioural responses of pest aphid species were studied in laboratory and field experiments. In alarm pheromone assays the peach-potato aphid, Myzus persicae Sulzer, and the pea aphid, Acyrthosiphon pisum (Harr), showed a lower level of response to the oil than expected given the high levels of (E)-beta-farnesene. It was shown that minor components in the oil, (+)-bicyclogermacrene and (-)-germacrene D, caused inhibition of the alarm response for M. persicae and A. pisum respectively. Nevertheless, in olfactometer studies the oil was directly repellent to A. pisum and the grain aphid, Sitobion avenae F. Sitobion avenae was not only repelled by (E)-beta-farnesene but also by (-)-germacrene D. Furthermore, although it was not directly repellent to M. persicae, the oil interfered with its attraction to host plant stimuli. In field plot experiments, numbers of A. pisum were significantly reduced in plots treated with a slow release formulation of the oil, when compared with control plots. (c) 2005 Society of Chemical Industry.

Is the (E)-β-farnesene only volatile terpenoid in aphids?

Abstract: Herbivore insects use a broad range of chemical cues to locate their host to feed or to oviposit. Whether several plant volatiles are effective allelochemicals for insects, the latter also emit molecules which have infochemical role. The (E)-β-farnesene (EBF) is a well-known aphid alarm pheromone commonly found in all previously tested species. Analysis of the released molecules from 23 aphid species, mainly collected on their natural host plant from May to July, was performed by gas chromatography–mass spectrometry. While EBF was identified as the main volatile substance in 16 species, alone or associated with other molecules, the alarm pheromone was only a minor component of the volatile molecule pattern of five other species. Moreover, two species, Euceraphis punctipennis and Drepanosiphum platanoides, did not release EBF at all but other terpenes were identified. This original observation raised the question on the utility and the source of the non-EBF volatiles. Are these potential infochemical substances produced by the aphid or only absorbed from the host plant? Here we determined that terpenes released by insects were not only provided by the host plants. Indeed, Megoura viciae emitted additional molecules than the ones from several aphid species reared on the same host plant. Moreover, no systematic relation between the feeding behaviour of the aphid species and the volatile releases was observed. Aphid terpene composition and proportion would provide reliable cues to identify the emitting organism, plant or insect. The next step of this work will be to determine the infochemical role of terpenes found in the range of tested aphid samples to better understand the relations between the different tritrophic levels.

Effect of silicon applied to wheat plants on the biology and probing behaviour of the greenbug Schizaphis graminum (Rond.) (Hemiptera: Aphididae)

Abstract: The effect of silicon-treated wheat plants (Triticum aestivum L.) on the greenbug, Schizaphis graminum (Rond.) (Hemiptera: Aphididae) was evaluated. Plants were treated with silicon incorporated to the soil and by foliar spraying. Aphid development was evaluated by observing the duration of the pre-reproductive, reproductive and post-reproductive periods, as well as fecundity and longevity. Probing behaviour was investigated by using the DC electrical penetration graphs (EPG) technique and a "honeydew clock". Silica treated plants had a clear adverse effect on aphid development. Stylet penetration was not affected by treatments showing no physical barriers by the plant tissue. However, stylet was withdrawn more often on plants treated with silica, resulting in reduction of probing time. Sieve elements were reached equally by aphids in all treatments and the insects remained ingesting phloem sap for similar periods. However, honeydew excretion was highly reduced indicating lower sap ingestion rate or higher sap retention inside the body. Chemical changes and induced resistance are possibly related to the reduction of aphid performance.

The effect of fractionated Tagetes oil volatiles on aphid reproduction

Abstract: The biological activity of essential oil volatiles from Tagetes minuta L. (Mexican marigold) against three aphid species was investigated in a series of laboratory experiments. The aphid species (Homoptera: Aphididae) studied were: Acyrthosiphon pisum (Harris) (pea aphid), Myzus persicae (Sulzer) (peach-potato aphid), and Aulacorthum solani (Kaltenbach) (glasshouse and potato aphid). Tagetes minuta oil volatiles significantly reduced aphid reproduction (up to 100% after 5 days of exposure). The effect depended on the quantity of essential oil used, and varied with the aphid species tested. Pea aphids were the most susceptible. Tagetes minuta oil was fractionated by vacuum distillation. Fractions and three pure compounds (limonene, (Z)-ocimene, and β-caryophyllene) were tested using the same experimental technique. The chemical composition of the volatiles was investigated by headspace-solid phase microextraction-gas chromatography mass spectrometry (HS-SPME-GCMS), and the main constituents of the oil were identified. Overall, applied in equal quantity, fractions predominantly containing sesquiterpenes and oxygenated monoterpenoids were more effective in restricting aphid population growth than fractions predominantly containing monoterpenes. When tested as a pure compound, the sesquiterpene β-caryophyllene produced a greater effect than the monoterpenes limonene and ocimene. The study demonstrates that T. minuta oil volatiles have potential for aphid control.

Abundance and natural control of the woolly aphid Eriosoma lanigerum in an Australian apple orchard IPM program.

Abstract: Woolly aphid (Eriosoma lanigerum Hausmann) (Hemiptera: Aphididae), was monitored over three growing seasons (1995--1998) to assess its abundance and management under apple IPM programs at Bathurst on the Central Tablelands of NSW, Australia. Woolly aphid infestations were found to be extremely low in IPM programs utilising mating disruption and fenoxycarb for codling moth Cydia pomonella L. (Lepidoptera: Tortricidae) control. This was the direct result of increased numbers of natural enemies. No insecticides were applied for woolly aphid control. Under the IPM strategies tested the principal control agent was identified as European earwig (Forficula auricularia L.) (Dermaptera: Forficulidae). Earwigs in combination with Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) reduced woolly aphid infestations below the action threshold set by commercial growers. However, A. mali together with other flying natural enemies, e.g., ladybirds, lacewings and hoverflies, did not provide commercially acceptable control of woolly aphid in the absence of earwigs. Under the conventional spray program, using the broad-spectrum insecticide azinphos-methyl for codling moth control, the level of woolly aphid infestation increased with each successive season and biological control was not established. When azinphos-methyl was withdrawn, natural enemies migrated in and provided control of woolly aphid within one season. This is the first study to show that the biological control of woolly aphid can be achieved in a commercially viable IPM program.

Effects of jasmonate‐induced defenses in tomato on the potato aphid, Macrosiphum euphorbiae

Abstract: Jasmonates such as jasmonic acid (JA) are plant-signaling compounds that trigger induced resistance (IR) to a broad range of arthropod herbivores. JA-dependent defenses are known to reduce the growth and survivorship of many chewing insects, but their impact on piercing‐sucking insects such as aphids has not been extensively investigated. In this study, induced resistance was activated in tomato ( Lycopersicon esculentum Mill) (Solanaceae) using a foliar application of synthetic JA, and control plants were treated with carrier solution. The life parameters of individual potato aphids and their progeny ( Macrosiphum euphorbiae Thomas) (Hemiptera: Aphididae) were evaluated on the unsprayed leaves of plants in order to access the systemic effects of the foliar treatments. IR significantly reduced the longevity and net reproduction of adult aphids, as well as the percentage of juveniles to survive to maturity. These results indicate that JA application induces systemic defenses in tomato that have a direct negative impact on aphid survivorship. This study also examined aphid honeydew excretion, in order to evaluate the potential influence of induced resistance on aphid feeding behavior. The average honeydew production per aphid was comparable on plants with or without JA treatment, indicating that JA-dependent defenses did not deter feeding. This suggests that the observed effects of JA on aphid survivorship were due to antibiotic rather than antixenotic factors. In addition to studying the effects of JA treatment on a tomato cultivar that is susceptible to aphids, this study also examined the effects of exogenous application of JA on tomato plants that carry the aphid resistance gene, Mi-1.2 . JA application did not significantly enhance or inhibit aphid control on resistant tomato. These findings expand our understanding of the effects of JA-dependent defenses on piercing‐sucking insects, and of the potential interactions between induced resistance and R-gene mediated aphid resistance in tomato.

Predatory activity and spatial pattern: the response of generalist carabids to their aphid prey

Abstract: 1. The spatial distribution of cereal aphids infesting a field of winter wheat during the population establishment, development and decline phases were studied using a field-scale grid of sampling locations. 2. The distribution of two generalist predators, Pterostichus melanarius and P. madidus, were sampled contemporaneously. 3. Using spatial analysis by distance indices (SADIE), spatial pattern in the aphid population, predator activity–density, predator hunger and aphid predation was detected and mapped. 4. We tested the hypothesis that carabids and aphids were spatially associated with one another through predation. Aphid predation by individual beetles was detected using enzyme-linked immunosorbent assays (ELISA) and hunger was assessed by measurement of foregut weights. 5. Initially, there was a strong spatial dissociation between aphids and P. melanarius activity–density. While the aphid population was increasing there was a strong spatial association between aphids and both P. melanarius and P. madidus activity–density. During aphid population decline there was no measurable association between aphids and predatory activity–density. 6. Predation of aphids was strongly locally associated with predator activity–density on all sample dates for both predator species, regardless of the association with aphid spatial pattern. 7. Areas within the field most isolated from P. melanarius predation had the highest rates of aphid population increase. 8. Although the proportion of P. melanarius individuals consuming aphids was much lower compared to P. madidus, it was concluded that it was a more effective biological control agent due to its comparative abundance.

Honeydew production and honeydew sugar composition of polyphagous black bean aphid, Aphis fabae (Hemiptera: Aphididae) on various host plants and implications for ant-attendance

Abstract: The black bean aphid, Aphis fabae, is polyphagous and its life cycle involves seasonal migration between summer and winter host plants. The aphids are regularly tended by honeydew-collecting ants. This study investigates whether differences exist in honeydew production and honeydew sugar composition for A. fabae subspecies feeding on various host plants and whether such dif- ferences reflect differences in the intensity of ant-atttendance ( Lasius niger). A. f. fabae feeding on the perennial summer host, Tanacetum vulgare, produced twice the amount of honeydew (ca. 110 µg per aphid . h -1 ) than when feeding on the annual host plants Vicia faba or Chenopodium album. Honeydew production of A. f. cirsiia- canthoides feeding on the creeping thistle Cirsium arvense was the highest measured in this study (ca. 150 µg per aphid . h -1 ). Total sugar concentration in the honeydew of A. f. fabae did not differ when feeding on various summer hosts, whereas the honeydew of A. f. cirsiiacanthoides on C. arvense contained a significantly higher amount of total sugars. The trisaccharide melezitose was the dominant sugar in all the honeydew samples, except for the honeydew of A. f. fabae and A. f. evonymi feeding on the woody winter host plant Evonymus europaeus. The highest proportion of melezitose (80% of total sugars) was found in the honeydew of A. f. cirsi- iacanthoides feeding on C. arvense. In this subspecies, the intensity of ant-attendance was also highest. The results confirm our hypothesis, that the sugar richness of the honeydew (rate of honeydew secretion × total sugar concentration) along with the presence of the attractant sugar melezitose are the critical factors in determining the extent of ant-attendance. In A. f. fabae feeding on the spindle tree E. europaeus, the total sugar concentration of the honeydew as well as the sugar composi- tion differed significantly between generations.

Control of Invasive Soybean Aphid, Aphis glycines (Hemiptera: Aphididae), Populations by Existing Natural Enemies in New York State, with Emphasis on Entomopathogenic Fungi

Abstract: This study evaluated the diversity and abundance of existing natural enemies of soybean aphid, Aphis glycines L., under field conditions in New York State, with emphasis on entomopathogenic fungi. In 2003, five soybean fields were occasionally sampled to estimate abundance and species composition of entomopathogenic fungi. During 2004, five soybean fields and adjacent buckthorn were sampled weekly. Seven species of aphid pathogenic fungi were found, including Pandora neoaphidis (Remaud. et Henn.) Humber, Conidiobolus thromboides Drechsler, Entomophthora chromaphidis Burger et Swain, Pandora sp., Zoophthora occidentalis (Thaxter) Batko, Neozygites fresenii (Now.) Remaud. et Keller, and Lecanicillium lecanii, (Zimm.) Gams et Zare. P. neoaphidis was the most abundant species, causing 84% infection in an outbreak aphid population in 2003, after which the aphid population crashed. In 2004, we found the first aphids with fungal infections in late June to midJuly. Mycosis was strongly associated with ap...

Colonization of apple orchards by predators of Dysaphis plantaginea : sequential arrival, response to prey abundance and consequences for biological control

Abstract: Episyrphus balteatus (DeGeer) (Diptera: Syrphidae), Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) are the three most abundant natural enemies of Dysaphis plantaginea Passerini (Homoptera: Aphididae) in Asturian (NW Spain) apple orchards. They attack this aphid in sequence: E. balteatus arrived first, followed by A. bipunctata and then by A. aphidimyza. The cecidomyiids arrived too late to have a regulating effect. The syrphids laid an average of 2.3 ± 1.7 eggs per aphid colony and the coccinellids 18.4 ± 9.9 regardless of the degree of the infestation rates of the apple shoots. This value corresponds to the size of an egg batch laid by one female. Therefore, these aphid predators did not respond numerically to the abundance of the pest. The results of this study indicate that natural populations of syrphids and ladybird beetles are unable to control D. plantaginea, and therefore a more complex strategy than waiting for natural enemies is required.

Reduced response of insecticide-resistant aphids and attraction of parasitoids to aphid alarm pheromone; a potential fitness trade-off

Abstract: Response to the alarm pheromone, (E)-b-farnesene, produced by many species of aphids, was assessed in laboratory bioassays using an aphid pest, Myzus persicae (Sulzer), and its primary endoparasitoid, Diaeretiella rapae (McIntosh). This was done in three separate studies, the first investigating responses of a large number of M. persicae clones carrying different combinations of metabolic (carboxylesterase) and target site (kdr) insecticide resistance mechanisms, and the other two investigating the responses of young virgin female adult parasitoids. In M. persicae, both insecticide resistance mechanisms were associated with reduced repellence suggesting that each has a pleiotropic effect on aphid behaviour. In contrast, D. rapae females were attracted to the alarm pheromone source. The implications of this apparent fitness trade-off for the evolution and dynamics of insecticide resistance, and the potential for using beneficial insects to combat resistance development are discussed.

Effect of soil potassium availability on soybean aphid (Hemiptera: Aphididae) population dynamics and soybean yield.

Abstract: Studies were conducted to examine the effect of potassium (K) on soybean aphid, Aphis glycines Matsumura, population growth. A laboratory feeding assay examined the effect of K-deficient foliage on life table parameters of soybean aphids, and field experiments were designed to determine the effect of three soil K treatment levels on aphid populations and their impact on soybean yields. The feeding assay found that life table parameters differed between aphids feeding on the K-deficient and nondeficient soybean leaves. Soybean aphids in the K-deficient treatment exhibited significantly greater intrinsic rate of increase (r(m)), finite rate of increase (lambda), and net reproductive rate (Ro) relative to aphids feeding on nondeficient leaves. No significant difference was observed in mean generation time (T) between the two treatments. However, the field experiment repeated over 2 yr showed no effect of K on soybean aphid populations. Soybean aphid populations were high in unsprayed plots and feeding resulted in significant yield losses in 2002 at all three K treatment levels: when averaged across 2001 and 2002, unsprayed treatments yielded 22, 18, and 19.5% less than the sprayed plots in the low, medium, and high K treatments, respectively. No significant interaction was observed between aphid abundance and K level on soybean yields in either year. This study therefore suggests that although aphids can perform better on K-deficient plants, aphid abundance in the field may be dependent on additional factors, such as dispersal, that may affect final densities within plots.

Soybean Aphid, Aphis glycines Matsumura, a New Vector of Potato Virus Y in Potato

Abstract: Soybean aphid (Aphis glycines Matsumura), an exotic species first discovered in the North Central region of the United States in 2000, is a competent vector of severalPotyviridae. Soybean aphid has high fecundity and produces alatae (winged morphs) readily, characteristics typical of proficient virus vectors. When soybean aphids were exposed toPotato virus Y (PVY)-infected potato plants and then clip-caged on healthy potato plants in groups of five or as single aphids, PVY transmission ranged from 14% to 75% across all experiments. PVYo, PVYn, and PVPntn strains were transmitted by soybean aphid.

Life table and population parameters of Nasonovia ribisnigri (Homoptera: Aphididae) at different constant temperatures

Abstract: Age-speciÞc life tables of the lettuce aphid, Nasonovia ribisnigri (Mosley), feeding on lettuce were determined at different constant temperatures under controlled conditions. Our results showed that the proportion of alates increased with increasing temperatures, remaining below 7% at 16C and increasing to 40 Ð57% at a temperature above 20C. The longest developmental time of apterous aphids was obtained at 8C (31.5 d), and the shortest was at 26C (6.2 d), whereas the developmental time of alates was always 0.7Ð1.1 d longer than for apterous. Most aphids needed four instars to reach adult stage, but at 8, 26, and 28C, many individuals passed through Þve or six molts. Age-speciÞc survivorship (lx) was always above 90% at the temperature range of 16 Ð24C. Mortality rate (qx) was rather low but constant at 8C. However, mortality was high at 28C and occurred mainly in the last nymphal instars and adult stage. Unexpectedly, no nymphs were produced by the adult morphs at 28C, but effective fecundity was high at 8C. Fecundity for alates was always lower than for the apterous aphids at the same temperature. The largest intrinsic rate of natural increase (rm), and the mean relative growth rate (R GR) occurred at 24C, for both apterous and alate morphs, and the lowest at 8C. Our results show that lettuce aphid is better adapted to survive and reproduce at low (8C) than at high (28C) temperatures, and its best performance occurred at 20 Ð24C.

Molecular interactions between rosy apple aphids, Dysaphis plantaginea, and resistant and susceptible cultivars of its primary host Malus domestica

Abstract: The use of crop varieties resistant or tolerant to insect pests or other stress factors is one approach in non-chemical crop-protection. Knowledge of the biochemical and molecular background of insect-plant interactions is a prerequisite for optimizing breeding for resistance. However, the resistance genes involved in plant-aphid interactions have so far only been identified and characterized in very few plant species. Our work aims to elucidate the molecular and biochemical mechanisms involved in resistance of apple trees, Malus domestica L. (Rosaceae), against its primary aphid pest, the rosy apple aphid, Dysaphis plantaginea (Passerini) (Homoptera: Aphididae), which is considered a serious economic pest of apple. Gene expression in both resistant and susceptible apple cultivars after infestation with rosy apple aphids was investigated by employing the cDNA-AFLP method (cDNA-Amplified Fragment Length Polymorphism). From approximately 12 500 cDNA fragments detected on polyacrylamide gels, 21 bands were apparently up- or down-regulated only in the resistant cultivar 'Florina' after aphid infestation compared to the susceptible cultivar 'Topaz' and/or mechanically wounded or non-infested leaves. These fragments were cloned, sequenced, and the pattern of gene expression for six fragments was subsequently verified by virtual Northern blots. Sequence comparisons of these fragments to GenBank accessions revealed homologies to already known genes, most of them isolated from Arabidopsis thaliana L. Among them, a putative RNase-L-inhibitor-like protein, a pectinacetylesterase, an inositol-phosphatase-like protein, a precursor of the large chain of the ribulose-1,5-biphosphate-carboxylase, and defence-related genes such as a vacuolar H(+)-ATPase subunit-like protein and an ADP-ribosylating enzyme were identified. The results are discussed in relation to a putative role of these genes in conferring aphid resistance in apple trees.

An aphid-ant interaction : effects on different trophic levels

Abstract: The interaction between the aphid Aphis coreopsidis (Thomas) (Hemiptera, Aphididae) and the ant Camponotus sp.1 (Hymenoptera, Formicidae) on the plant Bidens pilosa L. (Asteraceae) was studied. We manipulated the presence of ants and other insects to understand the effects of this aphid-ant interaction on: (a) the growth of A. coreopsidis population, (b) the seed production of B. pilosa, (c) the density of predator spiders. The growth of the A. coreopsidis population was positively affected by attending ants, showing greater increase on ant-present control plants than on ant-excluded plants. The density of aphids on control plants was positively correlated with the density of attending ants, while the density of aphids on ant-excluded plants was positively correlated with the density of spiders. Plants with ants had a significantly lower quantity of viable seeds than those without ants. These results show that: (a) the presence of Camponotus ants reduces the number of predator spiders on B. pilosa, (b) the population of A. coreopsidis increases when attended by the ants, (c) this increase in aphid density as a result of ant attendance reduces the number of viable seeds of B. pilosa, and thus (d) an interspecific interaction between two species can have an indirect negative fitness effect on other partners.

Performance of Lipaphis erysimi (Homoptera: Aphididae) on different Brassica species in a tropical environment

Abstract: A 2-year study on the preference and performance of Lipaphis erysimi on different Brassica species in the field and under greenhouse conditions revealed that rapeseed (B. campestris var. BSH-1, B. campestris var. YSPB-9) and mustard (B. juncea RH-30) were better hosts for this aphid than other Brassica species (B. napus, B. nigra, Eruca sativa, B. carinata). On the first group of plants, the rate of nymphal development, longevity and fecundity of this pest were significantly less than on the second group of plants. Development was significantly prolonged when the aphid was reared on second group of plants.

Characterization of a facultative endosymbiotic bacterium of the pea aphid Acyrthosiphon pisum.

Abstract: The pea aphid U-type symbiont (PAUS) was investigated to characterize its microbiological properties. Fluorescence in situ hybridization (FISH) and electron microscopy revealed that PAUS was a rod-shaped bacterium found in three different locations in the body of the pea aphid Acyrthosiphon pisum: sheath cells, secondary mycetocytes, and hemolymph. Artificial transfer experiments revealed that PAUS could establish stable infection and vertical transmission when introduced into uninfected pea aphids. When 28 aphid species collected in Japan were subjected to a diagnostic PCR assay, four species of the subfamily Aphidinae (Aphis citricola, Aphis nerii, Macrosiphum avenae, and Uroleucon giganteus) and a species of the subfamily Pemphiginae (Colopha kansugei) were identified to be PAUS-positive. The sporadic incidences of PAUS infection without reflecting the aphid phylogeny can be best explained by occasional horizontal transfers of the symbiont across aphid lineages.

Application of DL-β-aminobutyric acid (BABA) as a root drench to legumes inhibits the growth and reproduction of the pea aphid Acyrthosiphon pisum (Hemiptera: Aphididae)

Abstract: DL-beta-aminobutyric acid (BABA) is a non-protein amino acid that is an effective inducer of resistance against a variety of plant pathogens. However, examples of BABA-induced resistance against insect herbivores have not been reported. We applied BABA as a soil drench to legumes and monitored its effects on the pea aphid Acyrthosiphon pisum (Harris). On tic bean (Vicia faba var. minor), BABA increased aphid mortality, caused a reduction in the mean relative growth rate of individual insects and lessened the intrinsic rate of population increase (rm). BABA also caused significant reductions in the growth rate of A. pisum on pea (Pisum sativa), broad bean (Vicia faba var. major), runner bean (Phaseolus coccineus), red clover (Trifolium pratense) and alfalfa (Medicago sativa). No direct toxic effects of BABA against A. pisum were found, and no phytotoxic effects that may have caused a reduction in aphid performance were detected. Possible mechanisms behind this BABA-induced inhibition of aphid performance are discussed.

Monoclonal antibodies reveal the potential of the tetragnathid spider Pachygnatha degeeri (Araneae: Tetragnathidae) as an aphid predator.

Abstract: The drive towards a more sustainable and integrated approach to pest management has engendered a renewed interest in conservation biological control, the role of natural enemy communities and their interactions with prey Monoclonal antibodies have provided significant advances in enhancing our knowledge of trophic interactions and can be employed to help quantify predation on target species The tetragnathid spider Pachygnatha degeeri Sundevall was collected from fields of winter wheat in the UK and assayed by ELISA for aphid proteins It was demonstrated that this spider did not simply consume greater quantities of aphids because it was bigger In addition, P degeeri contained significantly greater concentrations of aphid in their guts than other spiders, showing that aphids comprised a greater proportion of their diet Although P degeeri constituted only 6% of the spider population numerically, females and males respectively contained 16% and 37% of total aphid proteins within all spiders screened, significantly more than their density would predict These spiders also preyed upon aphids at a disproportionately high rate in June, during the aphid establishment phase, theoretically the best time for limiting growth in the aphid population Although less abundant than other generalist predators, the capability of these hunting spiders to consume large numbers of aphids highlights them as a more significant component of the predator complex than had previously been realized Limitation of aphid numbers early in the year by generalist predators provides more time for the specialist aphid predators and parasitoids to move in

Determining the Optimal Timing of Foliar Insecticide Applications for Control of Soybean Aphid (Hemiptera: Aphididae) on Soybean

Abstract: Field experiments were performed over 3 yr to examine the impact of insecticide application timing to control soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), populations and to prevent soybean yield losses. Experiments were conducted in early and late-planted soybean, Glycine max (L.) Merr. Insecticide applications were made based on soybean growth stages. In 2001, applications were made at V1, V3, R2, and R3 growth stages; in 2002 and 2003, applications were made at R2, R3, and R4 stages. Additional treatments consisted of an unsprayed control and a multiple spray treatment that received insecticide applications at 7-10-d intervals. Soybean aphid densities were recorded throughout the growing season, and yields were measured. Soybean aphid populations varied considerably across years and planting dates. In general, late-planted soybean exhibited higher aphid pressure than early planted soybean, and experiments in 2002 had lower aphid numbers than those in 2001 and 2003. The multiple spray treatment significantly increased yield over the control in four of the six experiments, the exceptions being 2002 late planted and 2003 early planted. This suggests that soybean aphid populations were not large enough to cause yield losses in these two experiments. The R3 spray treatment increased yield in three of the six experiments (2001 late planting, 2002 early planting, and 2003 late planting), the R2 spray treatment increased yield in two of six experiments (2001 and 2003 late plantings), and the V1 application increased yield over the control in the 2001 late-planted experiment. Results suggest that when aphid populations are high insecticide applications made at R2 and R3 plant stages are most effective in preventing yield loss.

Potential Winter Hosts of Soybean Aphid

Abstract: Species and cultivars of the genus Rhamnus and related genera in the Rhamnaceae were tested for their suitability as overwintering hosts of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). The tests were carried out in outdoor cages during the fall through spring of 2002–2003 and 2003–2004. Response of the aphid to the hosts varied from successful overwintering on three Rhamnus hosts to complete rejection of all species in other genera. Fall migrants (gynoparae), egg layers (oviparae), males and eggs were found on the exotic Rhamnus cathartica (L.), and native Rhamnus alnifolia L’Heritier and Rhamnus lanceolata Pursh. In the spring eggs hatched, colonies developed and spring migrants were produced on these hosts. Other Rhamnus spp. were accepted by fall migrants and some level of colony development occurred, but no overwintering eggs were deposited on them. The phenology of the production of the various morphs, egg deposition, and egg hatch are documented on the suitable hosts. The implications of our findings on soybean aphid ecology and management are discussed.

Tritrophic Interactions Among Bt (Cry3Bb1) Corn, Aphid Prey, and the Predator Coleomegilla maculata (Coleoptera: Coccinellidae)

Abstract: The ability of the transgenic corn rootworm resistant corn (Zea mays L.) hybrid, MON 863, to affect the predator Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) through the consumption of corn-fed aphid (Rhopalosiphum maidis, Homoptera: Aphididae) prey was examined in the laboratory. Aphid weight was used as an index of prey quality. Larvae of C. maculata were reared to pupation on aphids that had consumed transgenic or nontransgenic (susceptible) corn plants. Larval duration, survivorship to pupation, postmortem adult dry weight (taken at 30 d after eclosion), adult mobility, and fecundity were compared for C. maculata between treatments. Fitness parameters of C. maculata were similar between transgenic and susceptible treatments, despite a 33% reduction in the weight of aphid prey reared on MON 863. Using immunostrip tests, Cry3Bb1 was detectable in the leaves of MON 863 but not in the susceptible plant, aphids, or C. maculata that were fed aphids. We conclude that transgenic corn that...

Oviposition vs. offspring fitness in Aphidius colemani parasitizing different aphid species

Abstract: We measured the acceptance and suitability of four aphid species [Aphis gossypii Glover, Myzus persicae (Sulzer), Rhopalosiphum padi (L.), and Schizaphis graminum (Rondani)] (Homoptera: Aphididae) for the parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae). Female parasitoids parasitized fewer R. padi than the other three aphid species, and fewer offspring successfully completed development in R. padi than in the other three host species. Sex ratios of emerging adults were more male-biased from R. padi than from the other three aphid species, suggesting that R. padi is a poor quality host for this population of A. colemani. Ovipositing A. colemani encountered R. padi at a slower rate, spent more time handling R. padi, and parasitoid offspring died at a higher rate in R. padi compared to A. gossypii. Our results show that oviposition behavior and offspring performance are correlated. In each experiment, we tested the effect of the host species in which the parasitoids developed (parental host) on the number of hosts attacked, the proportion of each host species accepted for oviposition and the survival of progeny. Parental host affected maternal body size and, through its effect on body size, the rate of encounter with hosts. Other than this, parental host species did not affect parasitism.

Effect of Nitrogen Fertilizer on the Intrinsic Rate of Increase of Hysteroneura setariae (Thomas) (Homoptera: Aphididae) on Rice (Oryza sativa L.)

Abstract: We studied the intergenerational effects of nitrogen (N) fertilizer applications to rice plants on the size, fecundity, and intrinsic rate of increase (rm) of Hysteroneura setariae (Thomas). Treatments consisted of rearing aphids on rice plants receiving 0, 50, 100, and 150% of the standard N fertilizer rates. Adult females produced on the 0 and 150% treatments were transferred to new plants at 0 or 150% N levels to create a matrix of four treatments: 0–0, 0–150, 150–0, and 150–150%. Second-generation aphids produced on 150% N plants had significantly higher survivorship, fecundity, and rm regardless of the N treatment of plants that parents fed on. N levels had no observed effect on head width. Aphids reared on 0% N plants whose parents were also reared on 0% N plants had significantly shorter body lengths than aphids on all other treatments, including the 150–0% treatment, indicating that the effect of a high N diet was expressed in a second generation of aphids. Results are discussed in the context of aphid population outbreaks in rice fields and in greenhouses.

Detrimental and neutral effects of wild barley–Neotyphodium fungal endophyte associations on insect survival

Abstract: Neotyphodium (Clavicipitaceae: Balansieae) fungal endophyte infection does not always confer temperate grass resistance to insect herbivores, although reports indicate that over 40 species are adversely affected by its infection. Laboratory and glasshouse experiments were conducted to improve our knowledge of the anti-insect properties of Neotyphodium-infected (E+) non-commercial grasses, and E+ wild barley (Hordeum) specifically. Neotyphodium infection of four plant inventory (PI) lines of wild barley conferred resistance to Mayetiola destructor (Say) (Diptera: Cecidomyiidae), whereas none of the E+ wild barley accessions reduced the survival of Rhopalosiphum padi (L.) (Homoptera: Aphididae). Metopolophium dirhodum (Walker) (Homoptera: Aphididae) densities were significantly lower on the E+ clones of Hordeum brevisubulatum ssp. violaceum (Boissier and Hohenacker) (PI 440420), compared with densities on endophyte-free (E-) plants of this species in population growth experiments. Neotyphodium infection of three Hordeum bogdanii (Wilensky) PI lines did not confer resistance to M. dirhodum; however, one of these E+ lines (PI 314696) was resistant to this aphid in a second population growth experiment. Our results provide additional evidence that the outcome of a grass-endophyte-insect interaction is influenced by the host grass species or genotype, Neotyphodium species or genotype, and the insect species involved. They also reinforce this phenomenon for non-commercial grass-endophyte-insect interactions and underscore the potential role of endophytes in mediating wild barley-insect interactions and their potential to act as defensive mutualists.