Showing papers on "Aphididae published in 1995"
TL;DR: In this article, the authors tested thirty lectins against the pea aphid Acyrthosiphon pisum (Harris) (Homoptera, Aphididae: Macrosiphini) by scoring mortality and growth inhibition over the whole nymphal period (7 days at 20°C).
Abstract: Acute toxicity of thirty lectins was tested against the pea aphid Acyrthosiphon pisum (Harris) (Homoptera, Aphididae: Macrosiphini). Activity was measured on artificial diets containing moderate concentrations of lectins (10–250 μg/ml) by scoring mortality and growth inhibition over the whole nymphal period (7 days at 20°C). Most of the proteins tested exhibited low toxicity, but some induced significant mortality; these included the lectins from jackbean (Concanavalin A), amaranth, lentil and snowdrop. There was no direct correlation between toxicity and sugar specificity of the lectin; however, many mannose-binding lectins were toxic towards A. pisum. Concanavalin A was also tested on five other aphid species (Aphis gossypii, Aulacortum solani, Macrosiphum euphorbiae, Macrosiphum albifrons and Myzus persicae) at concentrations between 10–1500 μg/ml. Mortality was very variable from one species to another. Strong growth inhibition invariably occurred within this concentration range, although dose-response curves differed substantially between aphid species. The peptidase complement of A. pisum's digestive tract was also investigated, as well as the oral toxicity of some protease inhibitors (PIs) to this aphid. Most protein PIs were inactive, and no part of the digestive tract contained detectable amounts of endo-protease activity. This is in contrast to the strong amino-peptidase activity which was shown to occur predominantly in the midgut and crop portions of the digestive tract. The potential of lectins in transgenic crops to confer Host-Plant Resistance to aphids is discussed.
178 citations
TL;DR: The peak density of aphid populations was significantly dependent on aphid abundance at the time syrphid larvae became active, indicating the high predation potential of the beneficials as well as the importance of synchronisation.
162 citations
TL;DR: The monitored populations of the cabbage aphid, Brevicoryne brassicae, and the green peach aphid were monitored on broccoli interplanted with three leguminous cover crops and compared with broccoli without cover crop (clean cultivation), suggesting differential population growth rates and parasitism seen for M. persicae are a result of inhibition of D. rapae in the living mulches.
119 citations
TL;DR: These facts suggest that L. niger control their predation activities on aphids with regards to the densities of the attended aphids per worker, and that the ants prey on the aphid species producing less honeydew.
Abstract: The antLasius niger was observed collecting honeydew and preying on the two aphid speciesLachnus tropicalis andMyzocallis kuricola on the chestnut treesCastanea crenata. Observation determined how the antL. niger controlled their predation on the aphids in response to the density and honeydew-productivity of the aphids.Lachnus tropicalis was a better honeydew source thanM. kuricola forL. niger in terms of the amount of honeydew collected per unit time by the ants. The number of foraging workers on a tree increased with the number ofL. tropicalis on the tree, but not with the number ofM. kuricola. The density ofL. tropicalis perL. niger worker on a tree had a positive effect on the predation activity ofL. niger on both aphids, whereas the density ofM. kuricola per ant did not have any significant effect. The predation pressure by the ant which increased withL. tropicalis density, however, directed toM. kuricola rather than toL. tropicalis. These facts suggest (1) thatL. niger control their predation activities on aphids with regards to the densities of the attended aphids per worker, and (2) that the ants prey on the aphid species producing less honeydew. The effects of the ant predation on aphids and the importance of these predation effect in antaphids interactions were discussed.
111 citations
TL;DR: The diversity of putative clones fell significantly, the mean number of individuals per clone rose and clones became more exclusively associated with certain sites which suggests that long-distance migration may have less of a homogenizing effect than hitherto thought for this species.
Abstract: The grain aphid Sitobion avenae (F.) was collected from winter wheat and adjacent cocksfoot grass at two locations in southern England and at four times in the year (April-July). Genetic variation between individual aphids was then investigated using random amplified polymorphic DNA polymerase chain reaction. Individuals caught in wheat and cocksfoot during April provided very different and highly diagnostic banding patterns that were independent of location. This host-based genetic differentiability was less evident as the season progressed, largely as a result of genetic drift and local movement between adjacent host species, which appeared to be predominantely in the direction from cocksfoot to wheat. The diversity of putative clones fell significantly, the mean number of individuals per clone rose and clones became more exclusively associated with certain sites which suggests that long-distance migration may have less of a homogenizing effect than hitherto thought for this species.
96 citations
TL;DR: Variations in rates of parasitization were consistent with differences in aphid defensive behaviours; no ‘preference’ for any host type was evident when aphids were anaesthetized with carbon dioxide, and patterns of attack and host acceptance were species‐specific.
Abstract: We examined host evaluation behaviour in three species of aphid parasitoids, Ephedrus californicus Baker, Monoctonus paulensis (Ashmead), and Praon pequodorum Viereck (Hymenoptera: Aphidiidae). Mated females were provided with pairwise choices among three kinds of hosts in the laboratory: (green) pea aphid, Acyrthosiphon pisum (Harris), and a green and a pink colour morph of alfalfa aphid, Macrosiphum creelii Davis. Patterns of attack and host acceptance were species-specific. Females of E. californicus did not respond to the presence of aphids prior to making antennal contact. Variations in rates of parasitization (pea aphid>green alfalfa aphid>pink alfalfa aphid) were consistent with differences in aphid defensive behaviours; no ‘preference’ for any host type was evident when aphids were anaesthetized with carbon dioxide. In M. paulensis, the order of preference (pea aphid>green alfalfa aphid>pink alfalfa aphid) did not vary when aphids were immobilized, or presented in the dark, or both. Host movement did not influence the rate of attack by M. paulensis. In contrast, the ranked order of preference in P. pequodorum varied with circumstance. In the light, females attacked pea aphid and green alfalfa aphid with equal frequency, but parasitized significantly more of the former; both kinds of aphids were attacked and parasitized at higher rates than pink alfalfa aphid. In the dark, P. pequodorum females parasitized green and pink alfalfa aphids equally and at higher rates than pea aphids. Whereas E. californicus was more successful ovipositing in immobilized hosts, P. pequodorum females attacked and laid more eggs in normal than anaesthetized aphids. Patterns of host recognition and evaluation are compared across six species representing four genera in the family Aphidiidae.
73 citations
TL;DR: A genomic probe encompassing most of an esterase gene (E4) that is amplified in insecticide-resistant Myzus persicae was hybridized in situ to mitotic and meiotic chromosome preparations of aphid clones of known esterases type and resistance level, finding amplified sequences at five sites.
Abstract: Chromosomal location of the amplified esterase genes conferring resistance to insecticides in Myzus persicae (Homoptera: Aphididae)
72 citations
Book•
01 Jan 1995
TL;DR: The last volume dealing with the aphids of Fennoscandia and Denmark is as mentioned in this paper, which contains a host plant index and an index to all Latin names of the species treated in all six volumes.
Abstract: This is the last volume dealing with the aphids of Fennoscandia and Denmark. It treats the remaining species of Aphididae and the family Lachnidae and contains a host plant index and an index to all Latin names of the species treated in all six volumes. Like the first five volumes it contains keys and illustrations.
69 citations
TL;DR: Apterous adult and nymphal Rhopalosiphum padi (L.), previously reared on plants infected with barley yellow dwarf virus (BYDV), were subjected to eight perturbations to determine effects on aphid dispersal and pattern of local spread of BYDV to oats in greenhouse experiments.
Abstract: Apterous adult and nymphal Rhopalosiphum padi (L.), previously reared on plants infected with barley yellow dwarf virus (BYDV), were subjected to eight perturbations (wind, rain, herbicide, coccinellid predators, crowding, mechanical disturbance, drought, and virus-infected plants) to determine effects on aphid dispersal and pattern of local spread of BYDV to oats in greenhouse experiments. Viruliferous aphids, caged overnight on oat plants in a 25-plant area (infection focus) in the center of each 625-plant plot, were subjected to a given perturbation after cages were removed and then allowed to move freely within the plot for 2 d. Presence of virus-infected plants outside the infection focus provided indirect evidence of aphid movement and direct evidence of virus spread. All types of disturbances except rain caused movement of apterous aphids and spread of BYDV. For all except the rain perturbation, controls were pooled and compared by paired t-tests with means of three indices of infection pattern (incidence, total distance, and average distance) for each experimental treatment. Incidence of infection (number of infected plants located outside the infection focus) in treated plots was significantly greater than pooled controls for the crowding, predator, wind, and herbicide perturbations. Total distance of infection (the sum of distances from the central plant in the infection focus to each infected plant outside the focus) was significantly greater in mechanical disturbance, crowding, predator, drought, wind, and herbicide perturbations than in controls. Average distance of infection (total distance divided by incidence) in treated plots was significantly greater than in the pooled controls for the drought, wind, and virusinfected oat treatments.
68 citations
TL;DR: The response of D. rapae to the cabbage-CA complex and to CA alone was significantly greater than to the wheat-RWA complex and RWA alone, suggesting an innate odor preference for crucifer-feeding aphids.
Abstract: Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiidae) is a parasitoid of several aphid species, including the Russian wheat aphid (RWA),Diuraphis noxia (Mordvilko), and the cabbage aphid (CA).Brevicoryne brassicae (L.). The response of matedD. rapae females to odors from wheat, cabbage, and plant-host complexes was investigated using a four-choice olfactometer. Experienced parasitoids, but not inexperienced females, responded positively to odors of the wheat-RWA complex in a no-choice test. In choice tests, experienced parasitoids did not respond to odors of uninfested cabbage and wheat leaves, but did respond positively to aphid-infested plants and to aphids alone. The response ofD. rapae to the cabbage-CA complex and to CA alone was significantly greater than to the wheat-RWA complex and RWA alone, suggesting an innate odor preference for crucifer-feeding aphids.
67 citations
01 Jun 1995
TL;DR: This is the last volume dealing with the aphids of Fennoscandia and Denmark and contains a host plant index and an index to all Latin names of the species treated in all six volumes.
Abstract: This is the last volume dealing with the aphids of Fennoscandia and Denmark. It treats the remaining species of Aphididae and the family Lachnidae and contains a host plant index and an index to all Latin names of the species treated in all six volumes. Like the first five volumes it contains keys and illustrations.
TL;DR: Several strains of the entomopathogenic fungus Beauveria bassiana have been considered for use as microbial insecticides and its persistence and its effects on pea aphids and a non-target aphid predator were determined.
Abstract: Several strains of the entomopathogenic fungus Beauveria bassiana have been considered for use as microbial insecticides. Experimental sprays were conducted in an alfalfa field with an aphid-derived strain of B. bassiana to determine its persistence and its effects on pea aphids, Acyrthosiphon pisum (Homoptera: Aphididae) and a non-target aphid predator, Hippodamia convergens (Coleoptera: Coccinellidae). B. bassiana conidia persisted in the field for at least 28 days, when approximately 10% of the original inoculum was still present. In the lower canopy, more conidia were present than on other plant parts and they persisted longer on the leaves in this location. However, conidia were still abundant in the upper canopy, where 97.9% of the aphids and 95.5% of H. convergens larvae were found. Thus, both insect species were exposed to the fungus for at least 1 month. However, pea aphid populations were not affected by the fungus. The predator's incidence was reduced by 75-93% (depending on application rate) e...
TL;DR: The results show that the aphid-day unitage, properly interpreted in relation to the Aphid species involved and the growth stage of the crop, is a useful predictor of grain yield loss at harvest.
Abstract: Accurate prediction of yield loss caused by cereal aphids in small grains involves assessment of the aphid population density on plants, the duration of their feeding, and the growth stage of the crop at the time of feeding. In this research, aphid-day (one aphid feeding on one plant for 24 h) unitage was used as a standard to compare the effects of feeding by greenbug, Schizaphis graminum (Rondani), Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), and bird cherry-oat aphid (BCO), Rhopalosiphum padi (L.), on the growth and yield of spring wheat, Trificum aestivum L., to measure the degree of additivity of yield loss caused by aphid feeding on the same plants at several stages of plant growth, and to evaluate the adequacy of the aphid-day standard as a predictor of yield loss. Results of greenhouse experiments with a scaled series of aphid-day components (150 aphids x 2 d ; 75 x 4 d ; 50 x 6 d ; 25 x 12 d) of equal total value (300 aphid-days) showed that the three aphid species were similarly damaging to yield but that for RWA and BCO the 25 x 12 d combination was significantly (P ≤ 0.01) more damaging than the other aphid-day treatments for those species. The administration of escalating aphid-day dosages to plants concomitant with advancing plant growth stages (two-leaf, 300 aphid-days ; four-leaf, 400 aphid-days ; two-leaf + four-leaf, 700 aphid-days ; boot, 1200 aphid-days; two-leaf + boot, 1500 aphid-days ; milk, 200 aphid-days ; two-leaf + milk, 2300 aphid-days) revealed that yield loss caused by aphid feeding at two plant growth stages was usually significantly (P < 0.01) greater than that at a single stage, but was not fully additive simply as the arithmetic sum of the yield losses at the two stages. Yield losses due to aphid feeding (expressed as milligrams per 100 aphid-days) declined precipitously with advancing plant growth stage. These results show that the aphid-day unitage, properly interpreted in relation to the aphid species involved and the growth stage of the crop, is a useful predictor of grain yield loss at harvest. Relating cumulative aphid-days at successive plant growth stages to ultimate yield loss enables producers to make informed decisions about the need for and timing of rescue chemical treatments.
TL;DR: A lack of additivity in insect resistance was most likely due to a threshold effect of trichome density, with the density on the hybrid species below the level for the tree to be aphid resistant.
Abstract: Population sizes of insect herbivores on natural plant hybrids may be higher, lower, or intermediate to those on the parent species. I studied the biology and population dynamics of a species of free-living aphid (Pterocallis alni) in a hybrid zone of alder (Alnus sp.). The parent trees were Alnus glutinosa and A. incana and their hybrid was A. pubescens. Hybrid trees differed from parents in phenological and morphological characters. Leaf trichome density on hybrid trees was intermediate to trichome densities on A. glutinosa (high density) and A. incana (low density), and thus appeared to be inherited in an additive manner. High trichome density on A. incana resulted in very high mortality and eventual elimination of aphids colonizing this tree. Aphid populations on the hybrid A. pubescens were higher than on A. incana, but lower than on A. glutinosa. However, aphid susceptibility did not appear to be inherited in a strictly additive fashion, as there was a dominance deviation in favor of the susceptible parent. This lack of additivity in insect resistance was most likely due to a threshold effect of trichome density, with the density on the hybrid species below the level for the tree to be aphid resistant. Population differences on A. glutinosa and A. pubescens were not caused by differences in growth or reproduction of aphids between hosts. Cage-reared aphids on these two hosts had identical performance in five successive generations. The effect of caging probably reduced wind movement of trichomes and thereby reduced the probability of aphids being dislodged from their feeding site. Predator and parasitoid species responded in a similar manner to the aphids ; their numbers were intermediate on the hybrid hosts.
TL;DR: Nine separate experiments, four using Cu and five involving Cd treatments, showed little consistent effect of enhanced metal concentrations on several parameters of aphid growth and reproduction, and the high metal concentrations used appeared to have few deleterious effects on aphids growth, development and reproduction.
Abstract: The uptake patterns of cadmium and copper by the black bean aphid from its host-plant Vicia faba, grown under control and elevated metal treatments, were compared. Initial experiments demonstrated significant Cu and Cd accumulation by treated host-plants. Aphids feeding on treated plants accumulated Cd, but not Cu. Concentrations of Cu were significantly higher in the honeydew of aphids feeding on treated plants compared with controls, whereas those of Cd were not. The aphid thus dealt with Cu and Cd in different ways. Copper was primarily excreted in the honeydew and concentrations in body tissues did not increase. Cadmium accumulated within the body and little was excreted in honeydew. Nine separate experiments, four using Cu and five involving Cd treatments, showed little consistent effect of enhanced metal concentrations on several parameters of aphid growth and reproduction. In one Cu experiment, development period to maturity and reproductive rate were significantly enhanced, but the result was not repeatable in three subsequent experiments. Similarly, significant effects of Cd on the same parameters were shown in only one experiment out of five. The high metal concentrations used appeared to have few deleterious effects on aphid growth, development and reproduction. Results are discussed in the context of trace metal transfer between trophic levels in polluted ecosystems and the possible main transfer pathways for Cu and Cd are identified.
TL;DR: Under caged conditions in the glasshouse accessions of Brassica fruticulosa Cyrillo and B. spinescens Pomel were shown to have high levels of antibiosis resistance to all three aphid populations expressed in terms of low production of young, and in the field, very few aphids settled on the plants of these two Brassica species demonstratinghigh levels of antixenosis (non‐preference) resistance.
Abstract: The literature concerning the breeding of brassicas resistant to cabbage aphid (Brevicoryne brassicae L.) and the interaction between different cultivars and various populations of the insect is reviewed. Six Brassica accessions selected for their different responses to a population of Brevicoryne brassicae in England were tested in the glasshouse against three New Zealand populations of the insect. All six brassicas were also tested in the field at Lincoln, New Zealand. Under caged conditions in the glasshouse accessions of Brassica fruticulosa Cyrillo and B. spinescens Pomel were shown to have high levels of antibiosis resistance to all three aphid populations expressed in terms of low production of young. In the field, very few aphids settled on the plants of these two Brassica species demonstrating high levels of antixenosis (non‐preference) resistance. The cabbage ‘Derby Day’ and New Zealand rape ‘Rangi’ supported a rapid increase in aphid populations in the glasshouse and were heavily infes...
TL;DR: It seems probable that the missing synchronisation of syrphid oviposition with the beginning of the increase of aphid abundance was the main cause for the high aphid infestation in 1992.
TL;DR: Life tables of two successive generations of the spotted alfalfa aphid on a resistant cultivar indicated that aphids do not transmit the capacity to overcome resistance in a simple Mendelian fashion, and a mechanism involving the random transmission of internal symbionts required by this aphid to overcome alfaloa resistance is hypothesized.
Abstract: The specific mechanisms of host plant resistance in alfalfa, Medicago sativa L., to the spotted alfalfa aphid, Therioaphis trifolli f. maculata (Buckton), remain unknown despite three decades of research. Difficulties with Painter's commonly used concept of host plant resistance were avoided when the Salt/Doutt paradigm of host selection by a parasite was used instead. Mechanisms of host plant resistance proposed in the literature were reviewed with respect to this alternative concept. Published results on the effects of host plant resistance are not comparable across different studies because of arbitrary measurements used. This problem is avoided with the use of laboratory age-specific life tables. In this study, four alfalfa cultivars were tested for host plant resistance to the spotted alfalfa aphid at three temperatures, and the statistical tools needed for the analysis are presented. The intrinsic rate of natural increase ( r m) was used as the measure of aphid performance on each cultivar. At the same temperature, r m values of the spotted alfalfa aphid on susceptible plants were significantly higher than on resistant cultivars. A developmental threshold of 7.9°C was estimated from the data, and the optimal temperature for growth and reproduction of this aphid was ≈21°C. Life tables of two successive generations of the spotted alfalfa aphid on a resistant cultivar indicated that aphids do not transmit the capacity to overcome resistance in a simple Mendelian fashion. A mechanism involving the random transmission of internal symbionts required by this aphid to overcome alfalfa resistance is hypothesized.
TL;DR: Plant architecture influenced the time‐budget of the parasitoids which used leaves adjacent to the aphid colony for attacking aphids, and Oviposition success of A. funebris was influenced by instar‐specific host behaviour.
Abstract: The influence of plant architecture, host colony size, and host colony structure on the foraging behaviour of the aphid parasitoid Aphidius funebris Mackauer (Hymenoptera: Aphidiidae) was investigated using a factorial experimental design. The factorial design involved releasing individual parasitoid females in aphid colonies consisting of either 10 or 20 individuals of Uroleucon jaceae L. (Homoptera: Aphididae) of either only larval instar L3 or a mixture of host instars, both on unmanipulated plants and on plants that had all leaves adjacent to the colony removed. Interactions between the parasitoid and its host were recorded until the parasitoid had left the plant. The time females spent on the host plant and the number of eggs laid varied greatly among females. Host colony size significantly affected patch residence time and the number of contacts between parasitoids and aphids. Plant architecture influenced the time-budget of the parasitoids which used leaves adjacent to the aphid colony for attacking aphids. Female oviposition rate was higher on unmanipulated plants than on manipulated plants. No further significant treatment effects on patch residence time, the number of contacts, attacks or ovipositions were found. Oviposition success of A. funebris was influenced by instar-specific host behaviour. Several rules-of-thumb proposed by foraging theory did not account for parasitoid patch-leaving behaviour.
TL;DR: Observations show that environmental cues (temperature and photoperiod) as well as internal factors via host Aphid such as host aphid life cycle, aphid morph and host plant quality are involved in the induction of dormant stages in aphid parasitoids.
TL;DR: Significantly (p < 0.05) more Russian wheat aphids were found on wheat plants grown in lysimeters maintained at 15% soil water holding capacity (SWHC) in a rainout shelter than on plants in lynium maintained at 50 and 100% SWHC.
TL;DR: Observations suggest that the local distribution of A. svalbardicum is determined by summer thermal conditions, and within patches where the aphids occurred, densities were higher on flowers and flowering shoots than on non-flowering shoots.
Abstract: The distribution of the high arctic aphid Acyrthosiphon svalbardicum was found to have a distinct limit in the Kongsfjorden area of Spitsbergen; the probability of site occupancy increased with distance from the fjord mouth and decreased with distance from the shore. Superimposed on this general distribution pattern, sites that cleared of snow early in the polar summer were more likely to be occupied by aphids. The phenology of the aphid was significantly affected by small changes in microclimate over distances of a few metres. The aphid only occurs in the warmer parts of the region, but laboratory cultures were successfully reared on plant material collected from colder regions that the aphid does not presently occupy. These observations suggest that the local distribution of A. svalbardicum is determined by summer thermal conditions. On a smaller scale, within patches where the aphids occurred, densities were higher on flowers and flowering shoots than on non-flowering shoots.
TL;DR: The effect of host-alternation on genetic diversity in Canadian populations of the aphid Rhopalosiphum padi is examined to identify patterns of admixture on secondary hosts of resident clones and relatively invariant migrants from southern areas.
Abstract: Past allozyme studies have shown a very low level of genetic variation among aphid populations. Attempts have been made to link this lack of diversity to the biological characteristics of aphids. This study examines the effect of host-alternation on genetic diversity in Canadian populations of the aphid Rhopalosiphum padi. Allozyme analysis of 15 populations on the primary host and 14 on the secondary hosts revealed polymorphism at only three of 51 loci. Little geographical differentiation was observed among populations from a single host category. However, gene frequency differences were noted between populations on primary and those on secondary hosts at two of three polymorphic loci and the mean heterozygosity was substantially reduced on secondary hosts. This pattern might result from the admixture on secondary hosts of resident clones and relatively invariant migrants from southern areas. Alternatively, the decreased heterozygosity might result from either a selective disadvantage of heterozygotes on secondary hosts or their selective migration to other hosts.
TL;DR: Field experiments in which clip-caged apterae of Myzus persicae (Sulzer) were monitored on sugarbeet revealed that leaf age, plant age and infection of the host with beet yellows closterovirus (BYV) had very large effects on aphid performance (development, reproduction and survival).
Abstract: Field experiments in which clip-caged apterae of Myzus persicae (Sulzer) (Homoptera: Aphididae) were monitored on sugarbeet revealed that leaf age, plant age and infection of the host with beet yellows closterovirus (BYV) had very large effects on aphid performance (development, reproduction and survival). On healthy plants performance was much better on young, expanding heart leaves than on older leaves. Performance on senescent leaves was poor. When apterae were kept on young heart leaves all their lives (by moving clip-cages to younger leaves every 4 days) there was a strong negative relationship between aphid performance and plant age (measured as plant leaf number at birth). On plants inoculated with BYV apterae showed large improvements in performance. These occurred so rapidly that nymphs born at the time of virus inoculation could benefit as much as those born later. The sizes and between-leaf distributions of M. persicae populations which developed from standard numbers of colonists on whole plants in cages were consistent with the results of the clip-cage experiments. Alatae were less sensitive than apterae to differences in plant and leaf age. Implications of the results for BYV epidemiology and control are discussed.
TL;DR: While some populations showed variant alleles, allozynie electrophoresis did not group aphids from different geographic or host plant sources, nor indicate the presence of sibling species, and there was no absolute host specificity.
Abstract: Aphis gossypii Glover is morphologically variable and polyphagous, and is a vector of many plant viruses We investigated the ability of A gosxypii from different host plants and geographical areas within Australia to colonise a range of host plantr in the laboratory Samples differed in their success rates on particular laboratory hosts but there was no absolute host specificity Colonisation was significantly more likely it' the previous host was of the same species, but hosts of the same plant family were not equally suitable The success rate of colonisation increased when aphids were repeatedly transferred to plan(> of the same species, huggesting that conditioning was occurring When aphids were placed on "poor" hosts, such as broad bean, or on stressed plants, they gave birth to offspring which developed into very small "yellow dwarf" adults While some populations showed variant alleles, allozynie electrophoresis did not group aphids from different geographic or host plant sources, nor indicate the presence of sibling species
TL;DR: Electroantennogram responses (EAGs) to a range of plant volatiles were recorded from alate summer forms of the English grain aphid Sitobion avenae and the rose‐grain aphid Metopolophium dirhodum, revealing pronounced receptivities of the antennal olfactory sensilla for the green leaf volatile.
Abstract: Electroantennogram responses (EAGs) to a range of plant volatiles were recorded from alate summer forms of the English grain aphid Sitobion avenae and the rose-grain aphid Metopolophium dirhodum. This bioassay screens for potential semiochemicals which are involved in host plant selection. EAGs of both species reveal pronounced receptivities of the antennal olfactory sensilla for the green leaf volatiles. In S. avenae (£)-2-hexenal and hexanal elicit larger responses than the corresponding alcohols, whereas in M. dirhodum only the mono-unsaturated C6 aldehyde produces larger EAGs than the alcohol. In the remaining group of plant volatiles benzaldehyde, benzyl acetate, 2-phenylethyl acetate, linalool, citronellal and β-pinene elicit distinct EAGs from both species. Structure-activity relationships are especially evident in the S. avenae olfactory responses. The response profiles of the aphid species are similar, although species-specific traits occur.
TL;DR: An assessment was made of the antibiotic and antixenotic resistance of three cultivars of autumn flowering chrysanthemum to the aphid Aphis gossypii Glover, with Hero being the most susceptible, Surfine the most resistant and Purple Anne intermediate.
Abstract: An assessment was made of the antibiotic and antixenotic resistance of three cultivars of autumn flowering chrysanthemum (derived from Dendranthema morifolium (Ramat) Tzvelev and D. indicum (L.) Desmoulins) to the aphid Aphis gossypii Glover. Antibiosis was also assessed at the top, middle and lower leaves of the plant. The three cultivars showed a range of resistance with Hero being the most susceptible, Surfine the most resistant and Purple Anne intermediate. There was a trend for antibiosis to improve with position down the plant, however there were cultivar by position interactions. Antixenosis was assessed at two levels, the first being under conditions where the aphid had complete access to the plant in caged choice assays and the second being under conditions where the aphid only had host odour to assess under olfactometer choice conditions. Preferences under the caged choice conditions found Hero to be the most preferred cultivar while there was no preference shown between Purple Anne and Surfine. However, olfactometer assessments showed Hero to be the least preferred of the three cultivars and, again, no preferences could be found between Purple Anne and Surfine.
TL;DR: The results indicate that any odour discrimination between the two alternative host plants by their respective colonisers is not perceived at the level of the peripheral olfactory receptors.
TL;DR: The results of the paired t –test and probability model, coupled with the developmental responses in feeding trials, lead us to conclude that C. cubana exhibited a preference beyond that which was associated with body size for B. argentifolii over M. euphorbiae, whereas C. rufulabris demonstrated little or no such preference.
Abstract: The suitability of the whitefly Bemisia argentifolii Bellows & Perring and the potato aphid, Macrosiphum euphorbiae (Thomas), as prey for 2 indigenous species of Chrysopidae, Chrysoperla rufulabris (Burmeister) and Ceraeochrysa cubana (Hagen), was examined. The developmental time and percentage mortality were compared for each prey separately and mixed. Prey preference was also tested for each predator using 2 preference models as well as a paired t –test. The developmental period for C. rufulabris was shortest on a mixed diet of aphids and whiteflies, suggesting that the nutritional quality of each prey alone was inferior to that of the combined prey. Development of C. cubana was slowest and mortality was greatest on the aphid diet. Both species of chrysopids were able to complete development on immature life stages of the whitefly alone. Both species consumed greater numbers of whiteflies than aphids; however, the consumption of aphids increased with each new instar. This trend indicates that prey selection was strongly influenced by increases in body size. The results of the paired t –test and probability model, coupled with the developmental responses in feeding trials, lead us to conclude that C. cubana exhibited a preference beyond that which was associated with body size for B. argentifolii over M. euphorbiae , whereas C. rufulabris demonstrated little or no such preference.
TL;DR: The impact of native natural enemies, supplemented by augmentative releases of the green lacewing, Chrysoperia rufilabris Burmeister, and/or the cecidomyiid, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiaiidae), on the population dynamics of thegreen apple aphid, Aphis pomi De Geer, was assessed in a series of experiments.
Abstract: The impact of native natural enemies, supplemented by augmentative releases of the green lacewing, Chrysoperia rufilabris Burmeister (Neuroptera: Chrysopidae), and/or the cecidomyiid, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae), on the population dynamics of the green apple aphid, Aphis pomi De Geer (Homoptera: Aphididae), was assessed in a series of experiments conducted in north central Washington State, USA. In one trial, C. rufiabris alone was released at a rate of 200 eggs or first instar larvae per tree per week for 6 weeks; in a second experiment, it was released in combination with A. aphidimyza at rates of 400 eggs and 250 pupae respectively per tree per week. In a final trial, A. aphidimyza alone was released at a rate of 200 pupae per tree per week for the duration of the growing season. The dominant native natural enemies in the study area were Chrysopa nigricornis Burmeister, A. aphidimyza. Onus sp. (Hemiptera: Anthocoridae), and various species of Syrphidae, Chamaemyii...