Flight behaviour of the bird cherry aphid, Rhopalosiphum padi

Abstract Seasonal winged forms of the bird cherry aphid, Rhopalosiphum padi L., were flown in an automated flight chamber. During their maiden flights, autumn migrants (gynoparae) had a greater initial rate of climb than summer (exules) and spring migrants (emigrants). Autumn migrants, presented with a laterally-positioned green-illuminated target for 2.5 s during each minute of flight, flew for a longer period before responding to the target (110 min) than summer migrants (36 min), while spring migrants responded after an intermediate time (72 min). This period is equivalent to the migratory phase of flight. The summer migrants were maximally responsive to targets illuminated by green monochromatic light (X, 555 nm). Targets illuminated with ultraviolet (γλ 360 nm) were attractive during the migratory and green-responsive phases of flight, but infrared (γλ700 nm) wavelengths were not attractive. The results are discussed with respect to aphid behaviour in the field.     

Inheritance of photoperiodic response in the bird cherry aphid, Rhopalosiphum padi

Abstract. The photoperiodic induction of presexual females (gynoparae) and males of the aphid Rhopalosiphum padi (L.) was examined in single clones collected from different latitudes (N clone from Blair Atholl, 56.5N 3.1W; C clone from Leeds, 53.5N 1.4W and S clone from Exeter, 50.4N 3.3W). Critical night lengths (CNLs) for gynopara and male production (CNLs: 50% of maximum production) and inter-clonal differences, defined by the different forms of progeny produced at a single discriminating night length (12 h 30 min), were measured at 16 ± 1C. The aphid clones differed in CNL and in the morphs produced at the discriminating night length. These differences were used to investigate the inheritance of the photoperiodic response. In crosses between clones the photoperiodic response showed considerable overall variation. The variation in CNLs indicated that the photoperiodic response was unlikely to affect the overwintering success after long-distance movement of clones from one latitude to another.     

Diapause termination and egg hatch in the bird cherry aphid, Rhopalosiphum padi

Conclusion TastePROBE is a convenient and flexible electronic circuit designed to record action potentials from taste sensilla of insects. It facilitates the recording of slow potentials arising in taste sensilla, improves the signal to noise ratio, and preserves spike shapes. This new amplifier design combines excellent signal to noise ratio with complete compatibility as regards existing electrophysiological equipment.DC recordings have higher information content than filtered recordings. With DC recordings, spike shapes are not modified and thus better sorting is possible. Moreover, slow variations in the transepithelial potential (i.e. less than 10 Hz) are preserved. Both aspects are of considerable importance when studying the physiology of taste receptors.     

Migration of alate morphs of the bird cherry aphid (Rhopalosiphum padi) and implications for the epidemiology of barley yellow dwarf virus

Suction trapping data indicate three periods of migration of Rhopalosiphum padi in spring, summer and autumn. Four alate morphs are present at different times during the year. A comparison of data from suction traps operating at 12·2 and 1·5 m suggests a different behaviour of females in autumn with more being recorded at 12·2 than 1·5 m. Males, which are only present in autumn, were also more numerous at 12·2 m. During tests to measure barley yellow dwarf virus (BYDV) infectivity, only 9% of female R. padi reproduced on oat seedlings in autumn compared with 74% in summer. Tests on alate female R. padi trapped alive showed that in summer all were exules, but during the first half of September these were largely replaced by gynoparae so that in autumn only 5% of all R. padi trapped at 12·2 m were alate exules. The aerial densities of gynoparae and males were 10 times greater at 12·2 than 1·5 m while densities of alate exules were similar at both heights. It is suggested that gynoparae and males fly higher to increase the chance of finding a taller dispersed host plant. The implications for BYDV epidemiology of the behaviour and presence of the various R. padi alate morphs indicate that autumn-sown cereals emerging before mid-September are particularly at risk from colonisation by alate exules before the transition to a mainly sexual migrant population is complete. Alate exules introduce BYDV from comparatively local sources. The ratio of total R. padi to Sitobion avenae in suction trap samples in autumn usually exceeds 100: 1, but on crops it was only 10: 1. The ratio of alate exule R. padi to S. avenae in suction traps in autumn was only 12: 1, similar to that observed on crops.     

The time of determination of gynoparae and males in the bird cherry–oat aphid, Rhopalosiphum padi

Apterous exules of Rhopalosiphum padi which experienced short photoperiods only during the first half of their nymphal life all produced gynoparae which made up 57% of the offspring produced in the first 7 days of the mother's reproductive life. Short photoperiods during the second half of a mother's nymphal life did not induce the production of gynoparae. However, when short photoperiods were experienced throughout a mother's nymphal life significantly more gynoparae (82%) were produced. Ten per cent of the offspring of mothers that experienced short photoperiods only during their adult life developed into gynoparae. Of the offspring reared in short photoperiods, but born to mothers reared and kept in long photoperiods, 30% developed into gynoparae. When mothers were exposed to short photoperiods in their adult life and their offspring so treated, then 90% of the offspring developed into gynoparae. Males only occurred amongst the last offspring of mothers that experienced short photoperiods in either the first or the second half of their nymphal life.     

The effect of the systemic fungicide benomyl on survival and reproduction of the bird cherry aphid (Rhopalosiphum padi)

Weight gain and intrinsic rate of population increase (r_m) of Rhopalosiphum padi were measured on wheat plants given soil drenches of benomyl at various concentrations. Reduced weight gain occurred with concentrations as low as 3.125 ppm. Mortality of aphids significantly exceeded control mortality at 25 ppm, and no aphids survived concentrations above 50 ppm. Development time was extended at 12.5 ppm and above. Reductions in fecundity and r_m became statistically significant by 25 ppm. Topical application of benomyl at 100 ppm or above increased aphid mortality, which reached 97% at 400 ppm. Weight gain of aphids was also reduced by topical application at 100 ppm. A factorial experiment showed absence of interaction between the effects on aphid weight of soil drench application to plants and topical application to aphids.     

Reproduction and probing behaviour of the bird cherry‐oat aphid Rhopalosiphum padi on detached leaves and leaves on intact seedlings of the winter host,bird cherry Prunus padus

Video recording and electrical penetration graph techniques are used simultaneously to investigate host acceptance (in terms of reproduction) and probing activities of autumn migrants (gynoparae) of the bird cherry‐oat aphid Rhopalosiphum padi (L.) on detached leaves and on leaves on intact plants of the winter host, bird cherry Prunus padus. There are no significant differences between the times taken to first parturition or the number of nymphs produced over a 6‐ or 18‐h period on intact plants or detached leaves. Stylet probing activities (i.e. total probe duration, xylem ingestion, the time to first phloem contact and phloem salivation) are also similar in the two situations.     

The price of protection:a defensive endosymbiont impairs nymph growth in the bird cherry-oat aphid,Rhopalosiphum padi

Bacterial endosymbionts have enabled aphids to adapt to a range of stressors,but their effects in many aphid species remain to be established.The bird cherry-oat aphid,Rhopalosiphum padi(Linnaeus),is an important pest of cereals worldwide and has been reported to form symbiotic associations with Serratia symbiotica and Sitobion miscanthi L-type symbiont endobacteria,although the resulting aphid phenotype has not been described.This study presents the first report of R.padi infection with the facultative bacterial endosymbiont Hamiltonella defensa.Individuals of R.padi were sampled from populations in Eastern Scotland,UK,and shown to represent seven R.padi genotypes based on the size of polymorphic microsatellite markers;two of these genotypes harbored H.defensa.In parasitism assays,survival of H.defensa-infected nymphs following attack by the parasitoid wasp Aphidius colemani(Viereck)was 5 fold higher than for uninfected nymphs.Aphid genotype was a major determinant of aphid performance on two Hordeum species,a modern cultivar of barley H.vulgare and a wild relative H.spontaneum,although aphids infected with H.defensa showed 16%lower nymph mass gain on the partially resistant wild relative compared with uninfected individuals.These findings suggest that deploying resistance traits in barley will favor the fittest R.padi genotypes,but symbiontinfected individuals will be favored when parasitoids are abundant,although these aphids will not achieve optimal performance on a poor quality host plant.     

Effect of gramine in the resistance of barley seedlings to the aphid Rhopalosiphum padi

Gramine (N,N-Dimethyl-3-aminomethylindole) content in various barley cultivars varied from 0 to 2.6 mmoles/kg fresh weight. Those cultivars which were lacking gramine were the most susceptible to the aphid Rhopalosiphum padi (L.). The population growth rate of R. padi negatively correlated with gramine content in leaves of barley seedlings. In addition, gramine incorporated in artificial diets decreased survival, amount of diet ingested and reproduction of aphids at concentrations similar to those found in plant leaves. Thus, it is suggested that gramine may be one of the factors responsible for the resistance of barley seedlings to R. padi.

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Résumé La teneur de gramine (N,N-dimethyl-3-aminomethyl-indole) dans différentes cultures de seigle présente des variations comprises entre 0 et 2,8 mmoles/Kg (poids frois). Les varietés dépourvues de gramine sont plus sensibles à l'attaque des pucerons. Le taux de croissance de la population des Rhopalosiphum padi a une correlation négative avec la teneur en gramine des feuilles de plantules de seigle. D'ailleurs, la gramine diminue les taux de nourrissement, de survie et de réproduction des pucerons alimentés avec des diètes artificielles contenant des concentrations du produit testé, similaire à celles trouvées pour les feuilles des plantes. Donc, on suggèrent que la gramine peut être un des facteurs responsables de la résistance des plantules de seigle contre l'attaque de Rhopalosiphum padi.

     

Population growth rate and relative virulence of the two South African biotypes of Russian wheat aphid,Diuraphis noxia,and bird cherry‐oat aphid,Rhopalosiphum padi,on resistant and non‐resistant barley

In South Africa a new biotype of the Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae), RWASA2, has appeared which exhibits an improved performance compared to the original biotype (RWASA1) on wheat containing the Dn1 resistance gene. We examined population growth rates as well as damage caused by RWASA1 and RWASA2, in addition to a different aphid species, the bird cherry‐oat aphid (BCA), Rhopalosiphum padi L. (Hemiptera: Aphididae), on three RWA‐resistant barley [Hordeum vulgare L. (Poaceae)] lines (STARS‐9577B, STARS‐0502B, and STARS‐9301B) and one susceptible control (PUMA). RWASA2 had a higher reproductive rate than RWASA1 on all barley lines tested, which is consistent with previous results on wheat. Two of the RWA‐resistant lines (STARS‐0502B and STARS‐9301B) also exhibited a similar resistance phenotype against BCA. In our experiments, severe chlorosis and leaf roll appeared earlier on the control PUMA barley variety as a result of RWASA2 feeding than was the case with RWASA1, probably due to the differences in reproductive rate. Although chlorosis appeared earlier on resistant plants after RWASA2 feeding, this symptom developed much faster during RWASA1 feeding on all three resistant lines tested. As chlorosis did not correlate well with aphid population numbers, we surmise that the differential chlorosis effects may be related to differences in the amount of saliva introduced by the two aphid clones during feeding. Our results indicate that the difference between RWASA2 and RWASA1 are broader than a ‘gene for gene’ interaction with the Dn1 resistance (R) gene in wheat, and that these biotypes also differ in important aspects of their biology.     

Ovariole number and fecundity for the two emigrating generations of the bird cherry-oat aphid (Rhopalosiphum padi) in Sweden

Abstract. 1. The number of ovarioles and the potential fecundity in first (fundatrigenia) and second generation emigrants of Rhopalosiphum padi (L.) was investigated.
2. The relationships between weight and host quality on ovariole number were investigated.
3. The first generation of emigrants had a greater number of ovarioles and a higher fecundity than the second.
4. There was a positive relationship between ovariole number and weight.
5. The number of ovarioles and weight decreased with decreasing host quality.
6. The results do not agree with a recently proposed reproductive strategy of aphids where the number of ovarioles are supposed to be independent of weight and host quality.
7. In years with a high initial population on bird cherry, the migration to grasses, e.g. cereals, will be earlier, probably larger and, to a greater extent, consists of aphids which have a higher reproductive rate than in years with a small initial number on bird cherry.     

大气二氧化碳浓度变化对禾谷缢管蚜种群动态的影响

利用开顶式熏气室研究了大气CO₂浓度和土壤水分对禾谷缢管蚜Rhopalosiphum padi (L.)种群动态的影响,并分析了禾谷缢管蚜密度与被处理小麦叶片化学成分的关系。结果表明：（1）禾谷缢管蚜种群密度随CO₂浓度升高而持续增大并与土壤水分密切相关,各CO₂浓度下均以60%田间持水量时的密度最大;（2）CO₂和土壤水分对小麦叶片化学成分有明显的影响,麦叶水分、可溶性蛋白质、可溶性糖、淀粉含量随CO₂浓度和土壤水分含量上升而增加,纤维素含量随CO₂浓度上升而增加、随土壤水分含量上升而降低,单宁、丁布（DIMBOA）含量在CO₂浓度为550 μl/L时最高,但单宁含量随土壤水分上升而增加,丁布含量在60%田间持水量时最低;（3）禾谷缢管蚜密度与叶片水分、可溶性蛋白质、可溶性糖、淀粉含量呈正相关,与丁布、单宁含量呈负相关。结论：在未来的气候条件下,随着CO₂浓度升高禾谷缢管蚜种群可能会持续增长,这种增长在半干旱区更加突出。禾谷缢管蚜种群增长的原因之一是大气CO₂和土壤水分条件改变了植物的化学成分构成。     

Population dynamics of the bird cherry‐oat aphid,Rhopalosiphum padi (L.), during the autumn and winter: a modelling approach

1 A simulation model was developed to investigate the inter‐relationship of factors influencing the population dynamics of the bird cherry‐oat aphid (Rhopalosiphum padi (L.)) in barley crops during the autumn and winter. 2 The model incorporated algorithms describing alate immigration, development and survival of adults and nymphs, fecundity and morph determination in newly born nymphs. 3 The model was validated against pest outbreaks in barley fields in south‐east England. 4 It simulated accurately the size of the outbreaks with predictions of peak aphid populations within 20% of the observed in all but one case. Similarly, all but one of the year‐sowing date combination predictions of timing of peak abundance fell within 14 days of the observed. 5 A sensitivity analysis of the model highlighted the relative importance of various population processes in determining simulated aphid population dynamics; decreasing mortality rates of apterous nymphs by as little as 5% over the autumn and winter increased peak densities by as much as 60‐fold, whereas increasing daily temperatures by only 1 °C more than doubled peak aphid abundance. 6 The model identified our understanding of the mechanisms of aphid mortality as a limiting factor in the accurate prediction of R. padi outbreaks in the field.     

Effects of the aphid Rhopalosiphum padi on the leafhopper Psammotettix alienus under laboratory conditions

The Japanese giant looper, Ascotis selenaria cretacea, is a serious defoliator of tea gardens in Japan. The females produce racemic (Z,Z)-6,9-cis-3,4-epoxynonadecadiene (epo3,Z6,Z9-19:H, main component) and (Z,Z,Z)-3,6,9-nonadecatriene (Z3,Z6,Z9-19:H, minor component). The orientation of the males to the synthetic pheromone placed in a trap was strongly disrupted by Z3,Z6,Z9-19:H or a mixture of its monoepoxy derivatives (epoxydiene mixture, EDM) impregnated in septa and placed around the trap. Based on this result, polyethylene tubes containing Z3,Z6,Z9-19:H or EDM were prepared and effect of these dispensers was examined in a field. Disruption of male orientation to synthetic pheromone traps was achieved in orchards permeated with Z3,Z6,Z9-19:H at dispenser density of 3000 and 5000 tubes ha^–1 (release rate: 0.55–0.61 mg day^–1 tube^–1) and with EDM at every tested dose, 250–5000 tubes ha^–1 (release rate: 0.25–0.39 mg day^–1 tube^–1). Furthermore, disruption of mating in tethered females was observed in these orchards; particularly, the mating was perfectly inhibited in the areas treated with EDM at 3000 and 5000 tubes ha^–1. This is the first formulation for the mating disruption of a geometrid pest.     

The potential of hydroxamic acids in tetraploid and hexaploid wheat varieties as resistance factors against the bird‐cherry oat aphid,Rhopalosiphum padi

The potential for exploiting natural wheat resistance to control the cereal aphid Rhopalosiphum padi, the most important aphid pest of small grain cereals in the UK, was investigated as an alternative approach to the use of insecticides. The investigation focussed on a group of secondary metabolites, the hydroxamic acids or benzoxazinones, present naturally as glucosides, but which hydrolyse on tissue damage to give biologically active aglycones, e.g. 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one (DIMBOA) which are associated with natural plant defence. These can be important for resistance against insects, fungi, bacteria and nematodes for a range of cultivated monocotyledonous plants and could ultimately be combined with other defence mechanisms to provide a general approach to cereal aphid control. Levels of hydroxamic acids, particularly DIMBOA‐glucoside, were determined in hexaploid (Triticum aestivum) and tetraploid (Triticum durum) wheat varieties and differences were found between species and varieties. The effect of feeding by R. padi on the level of hydroxamic acids in the leaf tissue was also investigated. Thus, after 24 h of aphid feeding, as an apparently localised hydrolytic defence reaction in the leaf, levels of DIMBOA‐glucoside decreased noticeably. When aphids were fed on sucrose solution containing low doses of DIMBOA there was a significant mortality compared to the sucrose control. However, the levels of and variation in hydroxamic acids in the wheat varieties investigated were insufficient for significant differences in aphid behaviour and development.     

Effects of host plant drought stress on the performance of the bird cherry-oat aphid, Rhopalosiphum padi (L.): a mechanistic analysis

Abstract.  1. The growth (increase in height and leaf number) of four grass species was reduced by a −0.5 MPa drought stress, but the performance of an associated herbivore, Rhopalosiphum padi (L.), was not affected consistently. The intrinsic rate of increase of R. padi was reduced by drought stress on three grass species, including Dactylis glomerata (L.), but was unaffected on Arrhenatherum elatius (L.). Therefore, there is no general relationship in the effect of plant drought on an insect herbivore, even among closely related host plant species.
2. Drought stress increased the quality of plant phloem sap, as indicated by increased sieve element osmotic pressure and essential amino acid concentrations. Thus, diet quality could not account for the reduced performance of R. padi under drought stress. The concentration of essential amino acids in the phloem of well-watered A. elatius was, however, lower than that of well-watered D. glomerata , correlating with the decreased performance of aphids on well-watered A. elatius .
3. There were no differences in aphid feeding duration between watering treatments or plant species but sap ingestion rates were reduced significantly under drought stress.
4. Using the measure of dietary amino acid concentrations and the estimate of sap ingestion, the essential amino acid flux through aphids was calculated. Compared with the flux through aphids feeding on well-watered D. glomerata , there was a reduction in aphids feeding on drought-stressed D. glomerata and drought-stressed A. elatius due to lower sap ingestion rates. The flux through aphids on well-watered A. elatius was also reduced due to low phloem essential amino acid concentrations. Thus, the performance of an aphid is correlated with the availability and accessibility of essential amino acids.     

Probing behavior of bird cherry-oat aphid Rhopalosiphum padi (L.) on native bird cherry Prunus padus L. and alien invasive black cherry Prunus serotina Erhr. in Europe and the role of cyanogenic glycosides

The probing behavior of bird cherry-oat aphid Rhopalosiphum padi was studied on its natural winter host in Europe, the bird cherry Prunus padus, and on the invasive black cherry Prunus serotina, on which spring generations of R. padi do not survive. The EPG-recorded behavior of R. padi on bird cherry and black cherry showed differences in crucial aspects of probing and feeding. The period of the pre-phloem penetration was twice as long and rarely interrupted in aphids on bird cherry as opposed to aphids on black cherry. On black cherry, there was a considerable delay between finding and accepting the phloem. Aphids that had sampled phloem sap either refused to ingest it or the ingestion periods were very short. Amygdalin and prunasin (cyanogenic glycosides present in leaves of Prunus) seriously impeded ingestion activities when applied in pure sucrose diet. The role of amygdalin and prunasin in winter host plant selection and host alternation in R. padi is discussed.