Xylem ingestion by winged aphids

When aphids and their host plant are incorporated in a DC electrical circuit, phloem and xylem ingestion register as separate waveforms of the electrical penetration graph (EPG) signal. Aphids are primarily phloem feeders; xylem ingestion is seldom reported but can be induced experimentally by fasting the insects in desiccating conditions. In experiments with the black bean aphid, Aphis fabae Scop., young winged (alate) and unwinged (apterous) virginoparous adults were collected from their natal host plants (broad bean, Vicia faba L.) and allowed 3-h continuous EPG-recorded access to V. faba seedlings. Several aphids (47% of both morphs) showed ingestion from phloem sieve elements. Alate aphids also showed frequent xylem ingestion (60% of individuals), but no apterous aphids exhibited this activity. The EPG technique involves attachment of a fine gold wire electrode to each insect, a process that may affect normal behaviour at the plant surface. However, when the technique was modified to monitor the stylet activities of freely-settled aphids, high levels of xylem ingestion by alates were also recorded. The results suggest that the developmental physiology of winged aphids somehow predisposes them to xylem ingestion, possibly as a result of dehydration during the teneral period. Alate aphids may reduce their weight by fasting before take-off, giving aerodynamic benefits, but making rehydration, via xylem uptake, a priority following plant contact.     

Identification of immature aphids by chromatography

• 1 Immature apterae of five species of cereal aphid were distinguished by ultraviolet examination of chromatograms of their fluorescent pigments.
• 2 Non-expert examiners could identify Metopolophium dirhodum, Sitobion fragariae and Rhopalosiphumpadi with a mean reliability of 98, 83 and 71% respectively; Metopolophium festucae and Sitobion avenae could be separated from the rest but not from each other.
• 3 All species gave consistent chromatograms whether reared on oats or on wheat: some species produced atypical traces if reared on certain grasses.

     

双七瓢虫对蚜虫捕食作用

【目的】研究双七瓢虫Coccinula quatuordecimpustulata(Linnaeus)对蚜虫的捕食习性,为其保护利用提供依据。【方法】采用13种蚜虫分别饲喂双七瓢虫1~4龄幼虫及成虫,观察记录24 h的捕食数量;选取大豆蚜Aphis glycines Matsumura、豌豆蚜Acyrthosiphon pisum(Harris)和白杨毛蚜Chaitophrus populeti(Panzer)分别对双七瓢虫进行饲养,记录瓢虫发育历期。【结果】双七瓢虫对供试的13种蚜虫捕食数量存在显著差异,其嗜食程度依照对蚜虫的日捕食生物量依次为:大豆蚜、菊小长管蚜Macrosiphoniella sanborni(Gillette)、月季长管蚜Sitobion rosivorum(Zhang)、豌豆蚜、甘蓝蚜Brevicoryne brassicae(Linnaeus)等;用大豆蚜和豌豆蚜饲养,双七瓢虫各虫态发育历期较短,用白杨毛蚜饲养则发育历期较长,3种蚜虫饲养的双七瓢虫,蛹均能正常羽化。【结论】双七瓢虫对供试蚜虫均有捕食行为,但捕食量存在明显差异;不同蚜虫对双七瓢虫的发育历期具有一定影响。     

两种麦蚜取食诱导小麦抗性品种后对后来取食蚜生物学特性的影响

刺吸式昆虫在刺吸作物韧皮部取食后会影响作物的正常生长发育,随着作物抗性及昆虫种类的不同,作物反过来也会对昆虫造成或正或反的影响,然而一种刺吸式昆虫取食后对后来者有什么样的影响目前尚不确定。本研究通过严谨的实验方法,即选定3个不同国家的小麦抗性品种98-10-30、Amigo和Batis,在所有条件严格统一的人工智能控制温室内,通过各处理在同一植株上先后不同的接蚜方式,分别测定了麦二叉蚜Schizaphis graminum (Rondani)和麦长管蚜Sitobion avenae Fab.在前期被蚜虫危害的抗虫品种98-10-30、Amigo和Batis上的发育历期、体重差及相对日均体重增长率(mean relative growth rate MRGR)等生物学参数。结果表明：品种不同,蚜虫在不同处理条件下取食作物时受到的影响也不同,即在品种98-10-30上,通过与前期不接虫的对照及前期接不同麦蚜的相关处理比较,麦长管蚜对后期取食的麦二叉蚜(MRGR=0.0974±0.0071)具有抑制作用,而麦二叉蚜对后期取食的麦长管蚜(MRGR=0.1614±0.0048)却有促进作用;在品种Amigo上,前期麦蚜的危害对麦长管蚜的取食具有促进作用,而在品种Batis上前期危害对麦二叉蚜的取食具有促进作用。同时明确了3个品种对两种蚜虫的抗性状况,即在前期无蚜虫危害时,品种98-10-30和Batis对两种麦蚜的抗性相当;在前期有麦蚜危害时,品种98-10-30对麦二叉蚜的抗性较好,而品种Batis对麦长管蚜的抗性较好;品种Amigo无论在任何处理下均对麦二叉蚜的抗性较好。     

Transmission of carrot mosaic virus by aphids

The transmission of the carrot mosaic virus (CMV) by the aphidsAcyrtJiosiphon pisum HARRÍS,Cavariela aegopodii SCOP, andMyzus persicae SULZ was proved experimentally. It was observed simultaneously that CMV has a non-persistent character. CMV can be transmitted already 2 min after acquisition feeding by the aphidsMyzus persicae SDLZ andCavariella aego-podii Scop. When the time of acquisition feeding is prolonged to 4 min, CMV is transmitted also by aphidAcyrthosiphon pisum HAREÍs. The host range of the investigated virus wasalso determined and its transmission to 8 plant species, belonging to 4 families, was achieved. On the basis of studies of the vector virus relationship and of the host range, further proof was given for the different character of the Australian Carrot motley dwarf virus, theApivm virus 1 Roland and CMV. The experiments showed that preliminary starving of the aphids for 1 h increases their ability to transmit the virus by 3–3%.     

Sampling for aphids by traps and by crop inspection

The catches of thirty aphid genera and species during 3 years in a suction trap at 40 ft and on a yellow cylindrical sticky trap at 5 ft at Rothamsted and Broom's Barn are tabulated. Suction-trap catches were the more consistent but both were more effective at recording the first seasonal immigration of Myzuspersicae (Sulz.) and Aphis fabae Scop, than the British Sugar Corporation crop-inspection scheme. The catches show the differential attraction to yellow by different species, the effects of local vegetation, and the seasonal distribution of aphids that are crop pests or potential vectors of viruses.     

Wing polymorphism in aphids II. Interaction between aphids

Summary A study has been made of the effect of crowding on both prenatal and postnatal control of wing development in aphids. In experiments on prenatal form control it was shown that brief controlled encounters of only a minute's duration between two adult aphids could cause them to switch from producing apterous to alate progeny. Aphids which had been exposed to contact with other aphids continued to produce alate progeny for several days. Evidence from a number of experiments suggests that the principle stimulus involved is tactile. In experiments on postnatal form control, it was shown that more alates developed among larvae which were reared together than among larvae reared in isolation.

---

Zusammenfassung In großen Blattlauskolonien werden leichter Geflügelte gebildet als in kleinen. Dafür gibt es zwei Ursachen. Bei hoher Dichte verändern die Aphiden die Physiologie der Pflanze dergestalt, daß bei den Läusen, die an ihr saugen, die Geflügeltenbildung gefördert wird; und bei hoher Befallsdichte vermehrt sich für die Aphiden auch die Wahrscheinlichkeit, stimulatorische Wirkungen aufeinander auszuüben. In der vorliegenden Arbeit wird die Natur und Wirkungsweise der Wechselwirkung zwischen Individuen von Aphis craccivora Koch untersucht.Die Blattläuse wurden bei 20° und 10stündiger Photoperiode in völliger Isolation auf kleinen Blattscheiben gehalten und weiter vermehrt, die—aus Blättern ihrer Wirtspflanze herausgestanzt — auf einer Nährlösung schwammen. Unter diesen Bedingungen brachten sie überwiegend ungeflügelte Nachkommen hervor. Zur Erzeugung geflügelter Nachkommen konnten sie durch kurze Begegnungen mit anderen Aphiden angeregt werden. In einigen Versuchen wurden die Blattläuse für verschiedene Zeitabschnitte in kleine Käfige zusammengesperrt, in anderen wurden sie herausgefangen und veranlaßt, in rascher Folge mehrere Male übereinander hinwegzukriechen. Beide Behandlungsweisen bewirkten, daß die Aphiden von der Produktion ungeflügelter zur Produktion geflügelter Nachkommen umschalteten. Eine Anzahl von Versuchen berechtigen zu der Annahme, daß weder visuelle noch olfaktorische Reize dabei mitwirken, und es ist zu vermuten, daß in der Hauptsache Berührungsreize den Ausschlag geben. Der Versuch, einen entsprechenden künstlichen Reiz zu setzen, hatte nur zum Teil Erfolg.Die Blattläuse, welche einem Kontakt mit anderen Läusen ausgesetzt gewesen waren, wurden täglich auf frische Blattscheiben weitergesetzt und ihre Nachkommenschaft auf den Blattscheiben aufgezogen, auf denen sie geboren wurde. Auf diese Weise ließ es sich zeigen, daß kurze Begegnungen zwischen Blattläusen mehrere Tage lang einen Einfluß auf die Form der Nachkommenschaft beibehalten können, die sie danach produzieren.Die Flügelentwicklung von Aphis craccivora kann auch während der postnatalen Entwicklung beeinflußt werden und es ließ sich nachweisen, daß auch hierbei die Wechselwirkung zwischen den Larven einen wesentlichen Faktor darstellt. Isoliert auf Blattscheiben aufgezogene Larven entwickelten sich weniger häufig zu Geflügelten als solche, die in Dichten von zwei oder mehreren je Blattscheibe gehalten wurden.

     

Infection of cereal aphids by the fungus Entomophthora

Three species of Entomophthora killed many Metopolophium dirhodum, M. festucae and Sitobion avenae on wheat at Harpenden, Hertfordshire, in 1971. Rainfall was low and aphid numbers were small in May and there was no Entomophthora infection. E. planchoniana first infected M. dirhodum early in June and the percentage of each aphid species infected increased during and after heavier rain in the first 2 weeks of June. M. dirhodum and S. avenae were most often infected by E. planchoniana, and the less common M. festucae mostly by E. aphidis and E. thaxteriana. Relative frequencies of E. aphidis and E. thaxteriana were largest before, and of E. planchoniana after, mid-July. The largest percentages infected were 53% of M. dirhodum and 30% of S. avenae during the second half of July and 60% of M. festucae in late June. The percentages of old nymphs and apterous adults that were infected were similar and only about half those of infected alatae.     

Effects of sinigrin on host selection by aphids

The feeding response of six aphid species to sinigrin, a mustard oil glucoside, was investigated. Sinigrin was a powerful phagostimulant for Hyadaphis = (Lipaphis) erysimi and Brevicoryne brassicae, whose host ranges are restricted primarily to the Cruciferae. H. erysimi was induced to feed on ten non-host species when leaves were systemically treated with sinigrin. To a lesser degree, the polyphagous Myzus persicae, which feeds widely among the Cruciferae, was stimulated to feed on sinigrin treated non-host leaves. Two polyphagous species, Aphis fabae and Acyrthosiphon = (Aulacorthum) solani, which are not pests of the Cruciferae, and the oligophagous Acyrthosiphon pisum which is restricted to the Leguminosae, were deterred by sinigrin-treated broadbean leaves, with the latter species showing the greatest response to treatment.Detailed studies with H. erysimi indicate that sinigrin affects several phases of feeding behavior. Initially, water vapor arrests flight activity of alates and incites test probing. Alate aphids detect sinigrin (topically applied to broadbean leaves) during test probes and subsequent behavior is similar to that on host leaves. Evidence from aphid penetration of solutions and electronic monitoring of feeding activities of H. erysimi apterae on systemically treated nonhost leaves suggests that sinigrin acts as a stimulant for stylet penetration and assists location of the phloem sieve elements.

---

Zusammenfassung Sinigrin, ein für Cruciferen typisches Senfölglukosid, wirkt phagostimulierend auf Hyadaphis (Lipaphis) erysimi, Brevicoryne brassicae und Myzus persicae, jedoch abschreckend auf Aphis fabae, Acyrthosiphon (Aulacorthum) solani und Acyrthosiphon pisum. Dies erklärt die Tatsache, daß die erste Gruppe häufig, wenn nicht ausschließlich, Cruciferen befällt, die zweite selten oder nie. Auf Nichtwirtsblätter, die mit Sinigrinlösung imbibiert sind, sprechen die oligophagen H. erysimi und B. brassicae bereits bei einer Konzentration von 0.001% an, während die polyphage M. persicae erst bei 1% positiv reagiert. Andererseits ist die oligophage A. pisum empfindlicher gegen Sinigrin als die polyphagen A. fabae und A. solani.Durch systemische Behandlung der Blätter mit 1%-iger Sinigrinlösung konnte H. erysimi auf zehn verschiedenen Nichtwirten zur Nahrungsaufnahme und Larviposition veranlaßt werden. In vier Fällen überlebten die Tiere während mindestens einer Generation. Auf Bohnenblättern konnten auf diese Weise 18 Generationen herangezogen werden, wobei allerdings die Größe der Adulten geringer, ihre Mortalität und Geflügeltenrate aber höher waren als bei der Aufzucht auf Weißen Rüben (Brassica rapa).Die Untersuchung des Wirtswahlverhaltens geflügelter H. erysimi ergab, daß Feuchtigkeit die lokomotorische Aktivität herabsetzt und Probestiche einleitet. Geflügelte Läuse können während der Probestiche (test probes) zwischen Wirten und Nichtwirten unterscheiden. Auf Rübenblättern wandern sie nach der ersten Probe in Richtung der Blattbasis und-unterseite. Auf Bohnenblättern wenden sie sich der Blattspitze zu und fliegen meist innerhalb 5 Minuten wieder weg. Auf sinigrinhaltigen Bohnenblättern verhalten sich die Läuse ähnlich wie auf Rübenblättern. Fütterungsversuche an Parafilmmembranen zeigten, daß die Anwesenheit von Sinigrin in der Nährlösung Tiefstiche begünstigt. In einer 1%-igen Sinigrinlösung wurden fünfmal mehr Speichelscheiden gezählt als im Blindversuch.Durch Registrierung des elektrischen Widerstandes zwischen Blattlaus und Substrat wurde das Eindringen der Stechborsten in pflanzliches Gewebe verfolgt und folgende Interpretation über das Einstechen und die Nahrungsaufnahme gegeben. An Rübenblättern nahm H. erysimi in den meisten Fällen von den Siebröhren Nahrung auf. Bei Bohnenblättern war der Einstich im allgemeinen weniger tief, und eine Nahrungsaufnahme erfolgte immer außerhalb der Siebröhren. Nach Sinigrinbehandlung wurden an Bohnenblättern in 50% der Fälle die Siebröhren erreicht.

---

---

Published with the approval of the Associate Director, Ohio Agricultural Research and Development Center, Journal article no. 103-71.     

Colonization of Tanacetum vulgare by aphids is reduced by earthworms

Soil organisms affect plant growth and chemistry and have subsequent effects on aboveground herbivore performance. However, whether herbivores discriminate between plants exposed to different soil organisms when colonizing their host plants is largely unexplored. In a greenhouse study, Tanacetum vulgare L. (Asteraceae) growing in a ruderal plant community in the presence and absence of arbuscular mycorrhizal fungi (AMF) and earthworms [Aporrectodea spp. (Haplotaxida: Lumbricidae)] was colonized by aphids [Myzus persicae Sulzer (Hemiptera: Aphididae)]. The aphids preferred to colonize plants without earthworms in the soil, and the numbers of aphids remained lower on the plants with earthworms, irrespective of the presence of AMF. Although the N, C, and P concentrations of the shoots were not affected by the soil organisms, AMF increased total aboveground biomass, total N, C, and P content, and photosynthetic activity (measured as electron transport rate) in the leaves under high light intensity. These results suggest that earthworms affect chemical cues that are used by aphids to judge host quality prior to feeding. Discrimination between plants with and without exposure to earthworms by aboveground herbivores is a novel aspect of plant‐mediated interactions between below‐ and aboveground organisms.     

Discharge by aphids of soluble secretions into dietary sources

Substances secreted by aphids into diets through a rubber-wax membrane can be detected by their absorption of low wavelength ultraviolet light. Their detection can be simplified by presenting water as diet. Of the substances secreted into water by non-crowded aphids within 24 h, ca 35–55% of the absorbance at 200 nm can be accounted for by reactions with protein reagents and/or electrophoresis. Macrosiphum euphorbiae secreted over 30 ng of salivary protein in bovine serum albumin equivalents per mg fresh body weight. SDS-PAGE revealed that the proteins initially secreted had subunits mostly of >100,000 Daltons. When dead or dying aphids were present on the membrane, however, e.g. due to crowding or prolonged confinement in the feeding chamber, additional subunits of <30,000 Daltons also appeared in the water. When feeding continued for more than 24 h, proteins, separable by electrophoresis began to disappear, possibly as a result of leakage of lyzing enzymes into the water from aphids that had died with their mouth parts still inserted through the membrane.The initial secretions possessed oxidase activity. Invertase was not detected but the secretion caused non-enzymatic reduction of a copper reagent used for detection of reducing sugars. Marked contrasts were noted between the electrophoretic protein patterns of the saliva of different species of aphids. The saliva of Macrosiphum euphorbiae and Myzus persicae contained over twice as much catechol oxidase activity per unit of salivary protein as that of Nasonovia ribisnigri and Aphis fabae.The significance of these findings in relation to use of artificial diets for colony maintenance and feeding experiments and for studies of aphid-plant interactions is discussed.     

Anomalous stylet punctures of phloem sieve elements by aphids

A deviating type of potential drop (pd), i.e. the electrically recorded intracellular punctures during the pathway phase of plant penetration by aphids, is described and discussed. This so-called repetitive pd (R-pd) has been observed in 4 aphid species, two on herbs and two on sycamore. Apart from a regular repetition with short intervals, the most characteristic feature of the R-pd is the middle intracellular part, i.e. sub-phase 2, which is extended, making the individual R-pd 2–3 times longer than the normal pd. Differences between the normal and R-pd are described, as well as differences within each pd type between species. The R-pd's seem to reflect repeated punctures of phloem sieve elements. Their biological significance is unknown.     

Electrical nature of recorded signals during stylet penetration by aphids

Electrical penetration graph, EPG, is a term suggested for recorded wave forms during electrically stylet penetration by aphids. The EPG appears to have two components with different electrical origin; i. e., resistance and electromotive force (emf). Fluctuating aphid resistance in series with the amplifier input resistor causes a fluctuating voltage due to dividing of a DC potential in the primary circuit. This circuit potential is composed of a supplied potential and potentials from the preparation such as half cell potentials at the electrode surfaces. The emf component consists of fluctuating potentials generated within the preparation itself. The value of the amplifier input resistance is rather critical; a high value in proportion to the aphid resistance favours the emf component, and a low value emphasizes the resistance component. Although resistance fluctuation forms the largest component of the signal, some parts of EPG patterns stem from emf. The DC method provides a more detailed signal than an AC system. The current through the aphids appears very low and is not likeley to influence feeding, or other biological functions of the aphid.

---

Propriétés électriques des signaux enrégistrés pendant les pénétrations au moyen des stylets des aphides.

Résumé Electro pénétration gramme, EPG, est le terme suggéré pour la méthode d'enrégistrement électronique de la pénétration des aphides. L'EPG est composé de deux origines électrique: la résistance variable, et la force électromotrice (fem). La résistance variable du puceron en serie avec la résistance d'entrée de l'amplificateur produit un voltage variable du à une division du potentiel électrique. Ce potentiel est composé d'un voltage appliqué, un potentiel de demi cellules sur les surfaces des électrodes, et de la composante fem déjà nommée. La valeur de la résistance de l'amplificateur est assez critique. Une valeur élevée de cette résistance par rapport à celle du puceron, favorise la composante fem, alors qu'au contraire une faible valeur accentue la composante de la résistance variable. Bien que cette résistance variable constitue en général la principale origine de l'EPG, quelques unes des ondes composantes, ou partis de celles ci, sont au contraire dues à la fem. Un montage au courant continu délivre un signal plus détaillé qu'un montage au courant alternatif, grâce a des proprietés de filtration de fréquence moins importante. Le courant traversant le puceron est très limité et ne semble pas agir sur l'ingestion, la salivation, ou sur d'autres functions biologiques.

     

Tuned protection of aphids by ants against a predatory hoverfly

1. Aphid‐tending ants that feed on honeydew have evolved strategies against aphidophagous insects and tune their aggressive behaviour according to the level of danger for their trophobionts. Here we investigate how Lasius niger Linnaeus (Hymenoptera: Formicidae) ants react to different instars of Episyrphus balteatus De Geer (Diptera: Syrphidae) hoverflies which vary in their voracity and defensive abilities. 2. During pairwise encounters, early syrphid instars (eggs, L1, and L2 larvae) elicited lower aggression scores compared to third larval instars (L3), which was intensively bitten by ants. L3 tried to escape from ants by releasing a sticky and toxic secretion over biting ants that died or underwent severe morbidity. 3. In a standardised system including the host plant, aphid, tending ant, and hoverfly, the ability of ants to protect an Aphis fabae Scopoli (Hemiptera: Aphididae) colony was evaluated. Early E. balteatus instars placed onto the plant elicited no mobilisation of ants, which often removed the hoverfly successfully. Eggs and early instars appeared as the weak links for integrated pest management by hoverfly auxiliaries. 4. In contrast, L3 induced the number of ant patrollers to increase at a local scale without any further recruitment from inside the ant nest. L3 syrphids were quite efficient at gluing ants with defensive secretions and at resisting to removal attempts by ants. 5. While supporting the assumption that ants tune their defensive response to the aphidophagous predator, the present results also showed a lack of efficient protection of their trophobionts from the most voracious late syrphid instar.