Showing papers on "Aphid published in 1994"
TL;DR: Differences in the performance of two out of five of the pea aphid clones could be explained by a part of the amino acid composition.
217 citations
TL;DR: Methyl salicylate, a volatile component ofPrunus padus, the winter host ofRhopalosiphum padi, was found to reduce colonization of the summer host by this aphid.
Abstract: Methyl salicylate, a volatile component ofPrunus padus, the winter host ofRhopalosiphum padi, was found to reduce colonization of the summer host by this aphid. The compound was identified by gas chromatographic analysis coupled with recordings from cells in the primary rhinarium on the sixth antennal segment of the aphid. Methyl salicylate eliminated the attractancy of oat leaves to spring migrants in olfactometer tests. In Sweden, this compound significantly decreased colonization of field grown cereals byR. padi and in the U.K., populations ofSitobion avenae andMetopolophium dirhodum were significantly lower on treated plots.
148 citations
TL;DR: Enzymelinked immunosorbent assay tests from citrus trees indicated that citrus tristeza virus incidence was low (<15%) in most areas and probably was caused by the use of infected budwood, rather than by aphid vectors, because of its random pattern of a few infected fields separated bytristeza-free fields.
Abstract: The brown citrus aphid, Toxoptera citricida (Kirkaldy), is distributed widely on citrus but is not known to occur in the Mediterranean region or, until recently, in North America. The brown citrus aphid is an important pest of citrus because it is an efficient vector of citrus tristeza virus. Surveys have shown that the brown citrus aphid has rapidly expanded its distribution in the Caribbean Basin and Central America. In September 1991, the brown citrus aphid was found widespread on citrus in Costa Rica, Nicaragua, and Panama but was not found in Belize, El Salvador, Guatemala, Honduras, or Mexico. In 1992, it was found in the Dominican Republic, Guadeloupe, Haiti, Martinique, Puerto Rico, St. Croix, St. Thomas, Trinidad, and the U.S. Virgin Islands and, in 1993, in Cuba and Jamaica. The aphid was not found in the Bahamas or Bermuda in the survey. Enzymelinked immunosorbent assay tests from citrus trees indicated that citrus tristeza virus incidence was low (<15%) in most areas and probably was caused by the use of infected budwood, rather than by aphid vectors, because of its random pattern of a few infected fields separated by tristeza-free fields. Most citrus tristeza virus isolates detected did not react with the severe-strain discriminating monoclonal citrus tristeza virus antibody, MCA13, and, thus, are probably mild strains. Some MCA13 reactive isolates were found in Belize, Costa Rica, Panama, Bermuda, the Dominican Republic, Jamaica, Puerto Rico, and Trinidad. The brown citrus aphid was ≍6-25 times more efficient in transmitting several strains of citrus tristeza virus than the melon aphid, Aphis gossypii Glover. Incidence of decline isolates of citrus tristeza virus could increase rapidly with the advancing movement of the brown citrus aphid and could threaten ≍180 million citrus trees on citrus tristeza virus-sensitive sour orange rootstock in the Caribbean Basin, Central America, Mexico, and the United States. An additional threat exists if this aphid begins to spread grapefruit and sweet orange stem-pitting strains of citrus tristeza virus.
131 citations
TL;DR: These results suggest that each worker of L. niger chooses aphid species to attend from her experience and may realize efficient collective foraging dependent on aphid density per worker.
Abstract: The following results on the behavior decision making of the antLasius niger toward two species of myrmecophilous aphidsLachnus tropicalis andMyzocallis kuricola on chestnut trees have been found. (1) An individual worker consistently attended only one aphid species, even if her nestmates attended other aphid species on the same tree. (2) The ants preyed less on the aphid species which they attended than on other myrmecophilous aphid species. (3) The ants preyed less on the aphids which had been attended by their nestmates, even if both aphids were the same species. (4) The ants preyed less on aphids which had provided honeydew to their nestmates. (5) The increased aphid density per ant led to an increase in the rate of predation on the introduced aphids by the ants. These results suggest that each worker ofL. niger chooses aphid species to attend from her experience. In addition, the workers can recognize whether an aphid has been attended by their nestmates and whether an aphid has given their nestmates honeydew. Through these processes, each worker decides to attend or to prey on the aphid. As a result, they may realize efficient collective foraging dependent on aphid density per worker.
108 citations
TL;DR: Estimates of predation indicated that the staphylinids Tachyporus spp.
Abstract: 1. The numbers of dead and live aphids falling to the ground in a cereal crop were estimated. The estimates showed that more live aphids fall to the ground than dead ones. 2. The availability of live aphids to predators which forage on the ground was low because aphids quickly returned to the crop canopy. This increased the relative availability of dead aphids. 3. Estimates of predation indicated that the staphylinids Tachyporus spp., which climb plants, were the most effective polyphagous predators. 4. Models comparing the potential availability of live aphids to climbing predators and ground predators indicated that predators such as Tachyporus spp. were able to contact more live aphid prey than were ground predators. 5. A comparison between polyphagous predators and aphid-specific hoverfly (Diptera: Syrphidae) larvae suggested that densities of syrphid larvae as low as 0.1 m-2 resulted in similar levels of predation to that accounted for by the polyphagous species measured in these field studies.
81 citations
TL;DR: A typical phloem‐feeding behaviour with an aphid‐like predominance of extracellular pathways of stylets is confirmed and similarities of EPGs from mealybugs with those of aphids and whiteflies allowed adoption of standard pattern labelling.
Abstract: The feeding behaviour of cassava mealybug (Phenacoccus manihoti) was analysed by the electrical penetration graph technique (EPG, DC-system) and by light microscopy. This study confirmed a typical phloem-feeding behaviour with an aphid-like predominance of extracellular pathways of stylets. Similarities of EPGs from mealybugs with those of aphids and whiteflies allowed adoption of standard pattern labelling. The main differences with aphid EPGs consisted of fewer but longer intracellular punctures (pd duration of 20 s vs 5-7 s for aphids), longer times to the first phloem-ingestion period and a lower motility of stylets within the phloem searching process. Comparison of the feeding behaviour on 6 plant types, including two occasional hosts (Talinum and poinsettia), one cassava hybrid and three common cassava cultivars (Manihot esculenta), allowed differentiation of penetration profiles. Intracellular punctures were shorter on occasional hosts, on which phloem finding and subsequent ingestion were markedly delayed although a great variability within plants persisted. Chemical analysis of some secondary plant substances revealed that none of the plants tested contained detectable amounts of alkaloids, and that cyanides were restricted to true hosts (cassavas and Manihot hybrid). Levels of total flavonoids did not differ between hosts and non-hosts, in contrast to those of phenolic acids. Preliminary correlations with EPG patterns are discussed.
80 citations
TL;DR: In a cottonwood (Populus) hybrid zone, Chaitophorus aphids attract aphid-tending ants which subsequently reduce herbivory by the leaf-feeding beetle, Chrysomela confluens, which causes beetle defoliation of immature trees.
Abstract: In a cottonwood (Populus) hybrid zone, Chaitophorus aphids attract aphid-tending ants which subsequently reduce herbivory by the leaf-feeding beetle, Chrysomela confluens. Observations and experimental manipulations of aphids and beetle larvae on immature cottonwood trees demonstrated that: 1) via their recruitment of ants, aphids reduced numbers of beetle eggs and larvae on the host; 2) these interactions occurred within a few days of the host being colonized by aphids; and 3) although aphid colonies were ephemeral, their presence resulted in a 2-fold reduction in beetle herbivory. The aphid-ant interaction is most important in the hybrid zone where 93% of the beetle population is concentrated (for reasons unrelated to aphids and ants). Because beetle defoliation of immature trees is high (ca. 25%), the indirect effect of aphids in reducing herbivory is likely more beneficial to trees in the hybrid zone than in adjacent pure zones where beetle herbivory is virtually absent. Tree genotype likely affects the impact of the aphid-ant interaction on trees within the hybrid zone, since levels of herbivory differ between sympatric Fremont and hybrid cottonwoods.
75 citations
TL;DR: A close agreement between larval growth rates in different host instars and adult reproductive performance suggests that, in A. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade‐offs in resource allocation.
Abstract: We determined the age-specific fecundity and survival of the solitary parasitoid wasp, Aphidius ervi Haliday (Hymenoptera: Aphidiidae), under constant laboratory conditions. Wasps were reared in each of the four nymphal instars of apterous pea aphids, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): (age 24 h), L2 (48 h), L3 (72 h), and L4 (120 h). Age-specific survival (lx) and fecundity (mx) differed between parasitoids developing in different aphid instars. The wasps' life-time reproductive success, as indexed by the intrinsic rate of population increase (rm), varied non-linearly with adult biomass and host size at parasitization. A close agreement between larval growth rates in different host instars and adult reproductive performance suggests that, in A. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade-offs in resource allocation.
67 citations
TL;DR: Phloem sap of wheat seedlings differing in whole leaf hydroxamic acid (Hx) concentrations was collected by cutting stylets of feeding aphids showing a tendency to be negatively correlated with aphid performance.
Abstract: Phloem sap of wheat seedlings differing in whole leaf hydroxamic acid (Hx) concentrations was collected by cutting stylets of feeding aphids. DIMBOA-glucoside was the only Hx-related product found. Concentration of DIMBOA-glucoside in phloem sap showed a tendency to be negatively correlated with aphid performance.
67 citations
TL;DR: The results suggest that the mechanism of resistance may be a mechanical blocking of the sieve element or stylets rather than a difference in the secondary plant chemistry of glucosinolates and phenolics.
Abstract: Feeding behaviour of the cabbage aphid, Brevicoryne brassicae, was monitored electronically on two resistant Brassica species, B. fruticulosa and B. spinescens, and compared with a susceptible control B. oleracea var. capitata cv. Offenham Compacta. Aphids, monitored for 10 h on the under side of leaves, performed recognizable feeding behaviour on all species. Electrical Penetration Graphs (EPGs) of aphids on resistant and susceptible plants showed no difference in behaviour for aphids on resistant Brassica species compared to susceptible until stylets penetrated the phloem sieve elements when a large reduction in the duration of passive phloem uptake (E2 pattern) on B. fruticulosa was indicated. Although feeding behaviour on 6 week-old plants of B. spinescens was similar to the susceptible controls, behaviour on 10 week-old plants was similar to that recorded for B. fruticulosa. The mechanism of resistance is thought to be located in the sieve element as the normal sieve element salivation (E1 signal was either quickly terminated by withdrawal of the stylets from the sieve element or continued as a disrupted E2 pattern. Analysis of secondary plant compounds in the three Brassica species only identified significant differences in the glucosinolate profile. No reproducible differences were detected in the concentration of phenolics or anthocyanins. The major glucosinolate component of B. fruticulosa and B. spinescens was gluconapin rather than glucobrassicin and glucoiberin as found in the susceptible host plant. However, both pure glucosinolates and glucosinolate extracts from all three species did not reduce aphid survival on chemically-defined artificial diets. These results suggest that the mechanism of resistance may be a mechanical blocking of the sieve element or stylets rather than a difference in the secondary plant chemistry of glucosinolates and phenolics.
67 citations
TL;DR: Host recognition is confirmed by chemical cues in the aphid cuticle that are detected during antennation, and host acceptance is dependent on an assessment of host quality during ovipositor probing.
Abstract: Host evaluation behaviour was examined in three species of aphid parasitoids, Aphidius ervi Haliday, A. pisivorus Smith, and A. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae). Parasitoids were provided under laboratory conditions with three kinds of hosts representing two aphid species: (green) pea aphid, Acyrthosiphon pisum (Harris), and green and pink colour morphs of the alfalfa aphid, Macrosiphum creelii Davis. Females of all three Aphidius species distinguished between aphids on the basis of colour, movement, and host species. Patterns of host acceptance by parasitoids were species-specific. In A. ervi, host preference was the same in light and dark conditions: pea aphid > green alfalfa aphid „ pink alfalfa aphid. In contrast, A. pisivorus attacked and accepted pea aphid and green alfalfa aphid equally in the light and preferred both of these over pink alfalfa aphid; however, it made no distinction between pea aphid and pink alfalfa aphid in the dark. Females of A. smithi attacked all three kinds of hosts (pea aphid > green alfalfa aphid „ pink alfalfa aphid) but apparently laid eggs only in pea aphid. The frequencies of attack and oviposition by all wasps were higher on ‘normal’ pea aphids than on those anaesthetized with CO2. Host recognition is confirmed by chemical cues in the aphid cuticle that are detected during antennation, and host acceptance is dependent on an assessment of host quality during ovipositor probing.
TL;DR: Two insecticide‐resistant clones of the closely related tobacco aphid Myzus nicotianae have elevated esterases indistinguishable from E4 and FE4 and amplified esterase DNA sequences, and flanking regions, with identical restriction maps to the M. persicae genes.
Abstract: Biochemical and molecular studies have established that in the peach-potato aphid, Myzus persicae, insecticide resistance is conferred by amplification of genes encoding the insecticide-detoxifying esterases E4 or FE4. Here we report that two insecticide-resistant clones of the closely related tobacco aphid Myzus nicotianae have elevated esterases indistinguishable from E4 and FE4 and amplified esterase DNA sequences, and flanking regions, with identical restriction maps to the M. persicae genes. Furthermore, the DNA sequences of c. 630 bp fragments of the E4 and FE4 genes of M. persicae are different from each other but identical to the fragment from corresponding M. nicotianae clones. The existence of apparently identical insecticide resistance genes in the two species can be best explained by the selection of the amplified genes in M. persicae, transfer to hybrids of M. persicae and M. nicotianae by sexual reproduction and subsequent spread through M. nicotianae populations.
TL;DR: The results indicate an approximately parallel increase of these properties during the period of aphid growth, consistent with the requirement of the endosymbiont for growth and reproduction of the aphid.
Abstract: The aphid Schizaphis graminum is dependent on its prokaryotic endosymbiont, Buchnera aphidicola. As a means of determining B. aphidicola numbers during the growth cycle of the aphid we have used the quantitative PCR to measure the number of copies of rrs (the gene coding for 16S rRNA, which is present as one copy in the B. aphidicola genome). In addition we have measured the aphid wet weight and the DNA and protein content. The results indicate an approximately parallel (23- to 31-fold) increase of these properties during the period of aphid growth. A 1-day-old aphid (24 mug [wet weight]) has 0.2 x 10 copies of rrs, while a 9-day-old aphid (497 mug [wet weight]) has 5.6 x 10 copies. The coupling of endosymbiont and aphid growth is consistent with the requirement of the endosymbiont for growth and reproduction of the aphid.
TL;DR: Evidence is provided for 6-methyl-5-hepten-2-one being one of the volatiles eliciting dispersal through the action of volatile chemical cues produced by the hyperparasitoids.
Abstract: Females of the parasitic waspAphidius uzbekistanicus, a specialist aphid primary parasitoid, react to the presence of their specialist hyperparasitoid enemyAlloxysta victrix by leaving the area. The wasps leave to increase their reproductive success, because only their offspring, but not the wasps themselves, are threatened by enemy attack. Furthermore, this dispersal is elicited through the action of volatile chemical cues produced by the hyperparasitoids. We provide evidence for 6-methyl-5-hepten-2-one being one of the volatiles eliciting dispersal. The tendency of the wasps to leave areas which are being colonized by their enemies reduces their efficiency as aphid antagonists.
TL;DR: An anholocyclic clone of the aphid Rhopalosiphum padi was reared on leaves of barley seedlings at 20 °C in a 16:8 LD photoperiod and observations were made on the rate of nymphal development, adult reproduction and longevity, and survival of progeny.
Abstract: An anholocyclic clone of the aphid Rhopalosiphum padi was reared on leaves of barley seedlings at 20 °C in a 16:8 LD photoperiod. First instar nymphs and newly moulted, pre-reproductive adults were cooled at 1°C min −1 to − 5 and − 7.5 °C, respectively, for 1 and 6 h to represent increasing levels of sublethal cold stress. Surviving aphids were returned to 20 °C and a 16:8 LD photoperiod, after which observations were made on the rate of nymphal development, adult reproduction and longevity, and survival of progeny. Mean development time from birth to adult increased with increasing cold stress, ranging from 6.6 ± 0.14 days in the control to 10.3 ± 0.14 days in nymphs exposed to − 7.5 °C for 6 h (...)
TL;DR: The results, together with those from previous studies, suggest that Aphidius ervi is best considered as a complex of differentiated populations, characterized by a varying degree of genetic divergence.
Abstract: The host preference and acceptance behaviour of populations of Aphidius ervi Haliday and A. microlophii Pennacchio & Tremblay from southern Italy was investigated. In no host-choice conditions, A. ervi females showed significantly higher attack and oviposition rates on the natural host Acyrthosiphon pisum (Harris) than on the non-host aphid Microlophium carnosum (Buckton)(Homoptera: Aphididae). In contrast, A. microlophii, which specifically parasitizes M. carnosum in the field, attacked both aphid species. However, dissections showed that oviposition of A. microlophii occurred only in a few of the attacked Acyrthosiphon pisum and was significantly less frequent than in M. carnosum. These results were confirmed in experimental host-choice conditions, suggesting that Aphidius microlophii oviposition is possibly regulated by a host haemolymphatic kairomone. Hybrids obtained by crossing A. ervi females with A. microlophii males attacked and oviposited in both aphid species, suggesting that these behavioural events have a strong genetic basis. The oviposition into host or non-host aphids did not elicit an immune defence reaction. The presence of the host's food-plant had no evident close-range effects on parasitoid attack and oviposition in non-host aphids. Aphidius microlophii reared on the non-host aphid Acyrthosiphon pisum produced a significant higher number of mummies after a few generations, suggesting a possible role of larval and early adult conditioning in the host selection process. These results, together with those from previous studies, suggest that Aphidius ervi is best considered as a complex of differentiated populations, characterized by a varying degree of genetic divergence.
TL;DR: A resistant barley was used to compare physiological responses of a susceptible barley to the recently introduced pest, Russian wheat aphid, Diuraphis noxia (Mordvilko), and well-watered PI 366450 showed greater stomatal closure in response to aphid infestation than ‘Morex’.
Abstract: A resistant barley ( Hordeum vulgare L., PI 366450) was used to compare physiological responses of a susceptible barley (‘Morex’) to the recently introduced pest, Russian wheat aphid, Diuraphis noxia (Mordvilko). As measured by chlorosis, leaf rolling, and streaking, damage by Russian wheat aphid was greater in ‘Morex’ than in PI 366450. The inhibition of growth, as measured by plant height, shoot dry weight, and number of leaves, also was greater in ‘Morex’ than in PI 366450. Relative water contents of leaves or stems showed no differences between ‘Morex’ and PI 366450 as a result of infestation. Well-watered PI 366450 showed greater stomatal closure in response to aphid infestation than ‘Morex’. However, the stomatal resistance responses of water-deprived PI 366450 and ‘Morex’ to Russian wheat aphids could not be distinguished. The two-dimensional SDS-PAGE protein profiles of uninfested ‘Morex’ and PI 366450 leaves were virtually identical. Upon infestation, a complex of proteins (≈23 kD) was altered in the PI 366450 profile and had decreased levels in ‘Morex’. Chlorophyll measurements indicated a greater relative loss of chlorophyll during infestation in ‘Morex’ than in PI 366450 when deprived of water; no differences could be distinguished when well watered. Measurements of the effectiveness of photosystem II to transfer electrons also showed no differences between well-watered resistant and susceptible barleys as a result of aphid infestation. However, the ability of the quinone pool in ‘Morex’ to recover after illumination was reduced greatly relative to that of PI 366450.
TL;DR: Analysis of interactions between parasitoids and different stages of Aphis fabae cirsiiacanthoidis Scop.
Abstract: Foraging behaviour and host-instar preference of young and old females of the solitary aphid parasitoid, Lysiphlebus cardui Marshall (Hymenoptera: Aphidiidae), were studied in the laboratory. The analysis of interactions between parasitoids and different stages of Aphis fabae cirsiiacanthoidis Scop. (Homoptera: Aphididae) revealed that encounter rates between aphids and parasitoid females and defence reactions of the aphids influenced the degree to which a particular aphid age class is parasitized. Encounter rates between hosts and parasitoid females depended on the foraging pattern of the parasitoid, which varied with age. In mixed aphid colonies patch residence time increased with parasitoid age. Furthermore, younger parasitoids (≤ 1 day old) laid more eggs into second and third instars, while older parasitoids (≥ 4 days old) did not show distinct host instar preferences. It is suggested that the oviposition behaviour of L. cardui is influenced by the physiological state, i.e. the age of the wasp.
TL;DR: Entomopathogen infection was the primary cause of an aphid population reduction that occurred during the week after peak aphid abundance, and continued pathogen activity combined with predation maintained aphids at a low density for the remainder of the season.
Abstract: The seasonal abundance patterns of the cotton aphid, Aphis gossypii Glover, and its complex of biological control agents on six cotton cultivars differed among cultivars during much of the growing season. Differences in aphid populations among cultivars were >3-fold during the period of peak aphid abundance. Lower aphid densities were found on cultivars exhibiting the smooth-leaf character. Parasitism and predation may have reduced cotton aphid population growth early in the season. Entomopathogen infection was the primary cause of an aphid population reduction that occurred during the week after peak aphid abundance, and continued pathogen activity combined with predation maintained aphids at a low density for the remainder of the season.
TL;DR: The performance of one clone of the pea aphid, Acyrthosiphon pisum (Harris), was assessed on 37 different cultivars and species of Pisum L. sativum cultivars, showing high local intraspecific variability in terms of host adaptation.
Abstract: The performance of one clone of the pea aphid, Acyrthosiphon pisum (Harris), was assessed on 37 different cultivars and species of Pisum L. In addition, random samples of 36 pea aphid clones collected on alfalfa and clover were tested on a selection of five Pisum sativum L. cultivars. Aphid performance was evaluated in terms of the mean relative growth rate (MRGR) during the first five days of life or other life history variables. The MRGR of the first-mentioned pea aphid clone differed little between cultivars. No significant differences in MRGR were found between wild and cultivated Pisum species or between modern and old P. sativum cultivars. There was considerable variation in host adaptation among the 36 pea aphid clones within each sampled field. The pea aphid clones showed no consistent pattern in performance on four of the five pea cultivars i.e. there was a significant pea aphid genotype — pea genotype interaction. On one of the cultivars all clones performed well. Pea aphid clones collected from red clover generally performed relatively poorly on pea cultivars, in contrast to the pea aphid clones collected on alfalfa. There was no difference in performance between the two pea aphid colour forms tested. Possible reasons for the high variation and the observed adaptation patterns are discussed. The fact that all clones were collected in two adjacent fields indicates that A. pisum shows high local intraspecific variability in terms of host adaptation.
TL;DR: Neem, Azadirachta indica (A. Juss.), seed oil (NSO) applied to leaf discs at a concentration of 1.0% resulted in 94% to 100% mortality of second instar nymphs of currant‐lettuce aphid, Nasonovia ribis‐nigri (Mosley), and green peach aphids, Myzus persicae (Sulzer), after nine days.
Abstract: Neem, Azadirachta indica (A. Juss.), seed oil (NSO) applied to leaf discs at a concentration of 1.0% resulted in 94% to 100% mortality of second instar nymphs of currant-lettuce aphid, Nasonovia ribis-nigri (Mosley), and green peach aphid, Myzus persicae (Sulzer), after nine days. The equivalent amount of pure azadirachtin (AZA) (a40 ppm), the principle active ingredient of neem, was as effective as NSO. The survival of adult aphids was unaffected by NSO or AZA, but the survival of offspring from treated adult M. persicae and N. ribis-nigri was reduced significantly. The lethal concentration of AZA resulting in 50% mortality of second instar nymphs of nine species of aphids ranged from 2.4 ppm for M. persicae on pepper to 635.0 ppm for the strawberry aphid, Chaetosiphon fragaefolii (Cockerell), on strawberry. For M. persicae, the growth regulating effect of AZA was influenced by the host plant and the nymphal instar treated.
TL;DR: In autumn 1991, aphid parasitoids of the genus Praon were caught in water traps with lures containing synthetic aphid sex pheromone components at three sites in England and one in Germany, and there was no evidence that any other genus of parasitoid responded to aphid Sex Pheromones at these sites.
Abstract: In autumn 1991, aphid parasitoids of the genus Praon (Hymenoptera; Braconidae) were caught in water traps with lures containing synthetic aphid sex pheromone components at three sites in England and one in Germany. At two of the English sites and at the German site, the traps were placed in winter cereal fields whilst the third English site was in woodland. Three species were caught, P. volucre, P. dorsale and P. abjectum. Those caught in cereal fields were almost entirely P. volucre, whilst P. dorsale dominated at the woodland site. Of the known aphid sex pheromone components, the most effective lure was the (+)-(4aS,7S,7aR)-nepetalactone. Nepetalactone traps placed at the woodland site in spring and summer caught few Praon females, and attraction may be confined to the autumn, when sexual female aphids are present in the field. Male parasitoids did not respond to the aphid pheromones at any time, although they were caught in suction traps operated at the woodland site during the autumn. At the cereal sites height had a significant influence on the efficiency of the pheromone traps, those placed just above the crop canopy being most effective. There was no evidence that any other genus of parasitoid responded to aphid sex pheromones at these sites.
TL;DR: In the course of a study on the primary symbiosis of the pea aphid Acyrthosiphon pisum, it is useful to further characterise the micro-organisms occurring in the aphid gut, and to comment on their possible origin and their presence at different ages and in two biotypes currently used in the laboratory.
Abstract: Most aphids possess symbiotic bacteria in specialised argans, the bacteriacytes occurring in tbeir haemocoele (Buchner, 1965). These Gramnegative bacteria, recently identified by malecular techniques as belanging to the y-3 subgraup af the Proteabacteria and named Buchnera aphidicola (Munsan et al., 1991b), are called the aphid primary symbiotes and have not been cultivated to date (Hauk, 1974; Munson et al., 1991b). They are cansidered as obligate symbiates of the insect, although viable but unfertile aposymbiotic aphids can be obtained in some species of aphids (Prosser & Douglas, 1991; Sasaki etai., 1991; Rahbe et al., 1992). Their association with Aphididae seems widespread, and is considered to be monophyletic since the origin of aphids, mare than 80 million years ago (Mun son et al., 199Ia). It is speculated that they canfer to their aphid hasts many metabolic advantages, leading to a beller adaptation to their ecolagical niche, i.e. phloem feeding (Houk & Griffiths, 1980; Campbell, 1989; Ishikawa, 1989; Douglas, 1990; Nardon & Grenier, 1993). The study of aphid primary symbiosis implies a characterisation of the micro-organisms involved, and their differentiation From ather microorganisms harboured by aphids. Actually, many aphid species also harbaur secondary symbiotic bacteria, maternally transmitted and located in sheath cells surrounding the primary bacteriomes (Houk & Griffiths, 1980). Molecular characterisation assigns them to the Enterobacteriaceae, a group which included E. coli and not Buehnera spp. (Unterman et al., 1989). Their function in aphid physiology is considered la be le" crucial since they are absent in many aphid species, such as Myzus persieae and Schizaphis graminum. Early reports also mentioned aphids with more than twa symbiotes (Buchner, 1965), and a recent paper describes an eukaryotic symbiosis in a species of gall-forming, social aphid belonging to the Hormaphidinae (Fukatsu & Ishikawa, 1992). Aside From their haemocoele symbiotes, sorne aphids have been reported to harbaur gut microorganisms (Schander! el al., 1949; Srivastava & Rouat!, 1963). Nothing is known on how widespread the infection s are, or on the function and origin of these micro-organisms. In the course of a study on the primary symbiosis of the pea aphid Acyrthosiphon pisum, we thought it useful ta further characterise the micro-organisms occurring in the aphid gut. We report here the observations and comment an their possible origin and their presence at different ages and in two biotypes currently used in our laboratory.
TL;DR: Eleven Brassica species and subspecies, as well as accessions of Arabidopsis thaliana and Eruca sativa, were evaluated for their resistance to the cabbage aphid in the field and laboratory at Horticulture Research International (HRI) Wellesbourne in 1992.
Abstract: Summary
Fifteen Brassica species and subspecies, as well as accessions of Arabidopsis thaliana and Eruca sativa, were evaluated for their resistance to the cabbage aphid, Brevicoryne brassicae, in the field and laboratory at Horticulture Research International (HRI) Wellesbourne in 1992. In the laboratory, aphid performance was measured in terms of pre-reproductive period, reproductive period, population increase and insect survival. Using these parameters it was possible to identify brassicas possessing antibiosis resistance. In the field B. brassicae attack was assessed in terms of numbers of insects and it was possible to determine aphid preferences for alighting on different species. High levels of antixenosis and antibiosis resistance were discovered in accessions of Brassica fruticulosa and B. spinescens, in a Brassica juncea breeding line and in Eruca sativa. Partial resistance was found in several other Brassica species. The potential of these various sources as donors of resistance genes to be bred into cultivated brassicas is discussed.
TL;DR: This paper combines experimental data on the reproductive biology of the monophagous aphid Uroleucon jaceae (L.) feeding on Centaurea jacea L. with theoretical considerations to predict the behaviour of this aphid when attacked by a predator.
Abstract: This paper investigates the influence of life-history traits on the defence reactions shown by aphids. In particular, we combine experimental data on the reproductive biology of the monophagous aphid Uroleucon jaceae (L.) feeding on Centaurea jacea L. with theoretical considerations to predict the behaviour of this aphid when attacked by a predator. In laboratory experiments we first determine the reproductive behaviour of this aphid on different plant developmental stages and plant qualities. In food deprivation experiments we examine the effect of different patterns of resource allocation to soma and gonads on the ability to survive without food. Aphids feeding on the shooting stage of high-quality plants had high reproductive rates and survived longest when deprived of food
TL;DR: Aphids most likely will be a limiting factor in canola production in the southern United States, particularly in the coastal plain region, and management activities should be directed at seedling and rosette stages of plant development.
Abstract: Canola, Brassica napus L., is being evaluated as a winter grain crop in the southeastern United States. The damage potential of insect pests was studied during three growing seasons in the Piedmont and coastal plain regions of Georgia by controlling insects with insecticides at the rosette, beginning bloom, or pod-fill stages of plant development. Canola pod infestations by the cabbage seedpod weevil, Ceutorhynchus assimilis Paykull, reached 60% at some sites in northern Georgia indicating that this insect will be an important pest of canola in this area. However, C. assimilis was not collected in any year in southern Georgia. Yield responses to insecticide treatments were associated with a complex of aphids, primarily the turnip aphid, Lipaphis erysimi (Kaltenbach), and green peach aphid, Myzus persicae (Sulzer), which caused direct injury to leaves and stems. Aphid injury reduced plant height and winter survival and delayed plant development. Comparison of untreated and season-long treated plots indicated that aphid injury reduced yield by 9.9, 30.4, and 34.8% in 3 yr in the coastal plain region. In northern Georgia, yield losses caused by aphids were ≤2.0% in three of four trials, but aphid injury reduced yield by 32.7% in one trial. Insecticidal control of aphids had the greatest effect on yield during the rosette stage with treatments at first bloom also enhancing yield in some trials. Insecticide treatments at pod-fill stage did not affect canola growth and yield in any trial. Aphids most likely will be a limiting factor in canola production in the southern United States, particularly in the coastal plain region. Aphid management activities should be directed at seedling and rosette stages of plant development.
TL;DR: C Cage experiments, in which the population increase of Metopolophium dirhodum was measured either in the absence or presence of the parasitoid Aphidius rhopalosiphi, showed reductions of peak populations in the Presence of the Parasitoid of 30% on the susceptible wheat cultivar Armada, but of 57%on the partially resistant Rapier.
Abstract: Summary
Cage experiments, in which the population increase of Metopolophium dirhodum was measured either in the absence or presence of the parasitoid Aphidius rhopalosiphi, showed reductions of peak populations in the presence of the parasitoid of 30% on the susceptible wheat cultivar Armada, but of 57% on the partially resistant Rapier. On both cultivars, aphid population curves in the presence and absence of the parasitoid diverged before the first mummies were formed. The number of aphids leaving plants was measured, and was found to increase in the presence of the parasitoid, particularly with Rapier (almost double). Most aphids (about 75%) which left plants fell, and a smaller proportion regained plants when parasitoids were present than when they were absent. A field experiment with Brevicoryne brassicae and natural predation on Brussels sprouts also showed an increase in aphids leaving a less susceptible compared with a more susceptible cultivar.
01 Jan 1994
TL;DR: Leaf surface pubescence is of questionable value in a greenbug; plant resistance program, but it is an effective resistance mechanism against the yellow sugarcane aphid.
Abstract: Observations during previous wheat germ plasm evaluation tests indicated that wheat lines with high levels of leaf pubescence are resistant to the yellow sugarcane aphid, Sipha flava (Forbes). Earlier work also suggested the same relationship for the green bug, Schizo phis germanium (Ronni), but the evidence was not as strong. This research studied the effects of leaf pubescence on the two aphid species in greater detail. Trix home length and density measurements were made on second and third leaves from seedlings of six pubescent wheat entries and two nearly glabrous wheat cultivars. Yellow sugarcane aphid and greenbug antibiosis and antixenosis tests were conducted using standard methods for the antibiosis test and new techniques for the antixenosis test. The results showed that leaf surface pubescence is of questionable value in a greenbug; plant resistance program, but it is an effective resistance mechanism against the yellow sugarcane aphid.