Efficacy of pymetrozine against Myzus persicae and in reducing potato virus Y transmission on tobacco plants

Forty‐four parthenogenetic lineages of Myzus persicae s.l. (Sulzer) from tobacco crops and peach orchards located in various regions of Greece were examined to determine their response to the insecticide pymetrozine using leaf‐dip bio‐assays. The results show that the aphid has not developed resistance, as all lineages exhibited resistance factors bellow 6.0. In transmission experiments of potato virus Y (PVY) using a lineage of the tobacco‐adapted subspecies M. persicae nicotianae Blackman on tobacco plants, one foliar application with pymetrozine provided adequate protection for 7 days. Pymetrozine significantly reduced both virus acquisition and inoculation compared with the untreated control and the reduction was comparable to a mineral oil application. These results are discussed in terms of the advantage of incorporating pymetrozine as a compound of pest management strategies against M. persicae s.l. and for control of non‐persistent viruses, especially in crops such as tobacco because of the high selection pressure from neonicotinoids resulting in potential of resistance developing in aphid populations.     

Blockage of stylet tips as the mechanism of resistance to virus transmission by Aphis gossypii in melon lines bearing the Vat gene

Aphis gossypii is the main virus vector in muskmelon crops. The melon gene Vat confers resistance to non‐persistent virus transmission by this aphid. The mechanism of this resistance is not well understood, but no relationship has been detected between resistance and the probing behaviour of aphids on resistant plants. Results presented here suggest that temporary blockage of aphid stylet tips preventing virus particle release may explain the resistance conferred by Vat gene. We performed experiments in which viruliferous aphids were allowed to probe different sequences of resistant (Vat‐bearing) and/or susceptible melon plants. The results demonstrated that A. gossypii inoculates Cucumber mosaic virus (CMV) efficiently in susceptible plants having previously probed resistant plants, showing that the resistance mechanism is reversible. Furthermore, the infection rate obtained for susceptible plants was the same (25%) regardless of whether the transmitting aphid had come directly from the CMV source or had subsequently probed on resistant plants. This result suggests that virus is not lost from stylet to plant during probing of resistant plants, supporting the temporary blockage hypothesis. We also found that the ability of Myzus persicae to transmit CMV is noticeably reduced after probing on resistant plants, providing evidence that this aphid species also responds to the presence of the Vat gene. Finally, we also found that in probes immediately after virus acquisition M. persicae inoculates resistant plants with CMV more efficiently than susceptible plants, perhaps because the Vat gene product induces increased salivation by this aphid.     

Analyses of the stomach deposit that develops in Myzus persicae feeding on sugar beet

Abstract .The white deposit, commonly found in the stomach of aphids that feed on sugar beet ( Beta vulgaris ssp. saccharifera L), turns a dark colour just prior to the death of the aphid, suggesting that chemical changes causing the deposit to darken may be associated with the death of the aphid. Chemical analyses of the white and dark stomach deposits by HPLC after hydrolysis, elemental analysis and FAB-MS, showed that the dark deposit is formed after the loss of hydrogen and oxygen from the organic white deposit, and that it appears to be a complex that is not dominated by any given compound. These results contrast with those of previous studies, in which the white precipitate was described as a polysaccharide or a mucopolysaccharide.     

The use of monoclonal antibodies to detect beet mild yellowing virus and beet western yellows virus in aphids

Information on infectivity of the aphids which invade sugar beet root crops each Spring is required for forecasting incidence and providing advice on control of virus yellows. Monoclonal antibodies, produced in the USA to barley yellow dwarf virus (BYDV) and in Canada to beet western yellows virus (BWYV), were used to distinguish between sugar-beet-infecting strains of the luteovirus beet mild yellowing virus (BMYV), and the non-beet-infecting strains of the closely-related BWYV in plant and aphid tissue. Totals of 773 immigrant winged Myzuspersicae and 124 Macrosiphum euphorbiae were caught in water traps in a crop of sugar beet between 25 April and 5 August 1990. Using the monoclonal antibodies and an amplified ELISA, 67%M. persicae and 19%M. euphorbiae were shown to contain BWYV; 8%M. persicae and 7%M. euphorbiae contained BMYV. In studies with live winged aphids collected from the same sugar beet field during May, 25 of 60 M. persicae and two of 13 M. euphorbiae transmitted BWYV to the indicator host plant Montia perfoliata; two M. persicae and two M. euphorbiae transmitted BMYV. In another study three of 65 M. persicae and one of three M. euphorbiae in which only BWYV was detected, transmitted this virus to sugar beet.     

棉蚜获毒后禁食对其保持并传播黄瓜花叶病毒的影响

采用棉蚜Aphis gossypii 甜瓜Cumumis melo 黄瓜花叶病毒（cucumber mosaic virus, CMV）体系,研究棉蚜获毒后在空气中禁食对其保持并传播黄瓜花叶病毒的影响。结果表明获毒后的禁食时间与棉蚜传毒效率呈负相关。运用EPG (electrical penetration graph)及其即时显示、即时中断技术研究分析棉蚜禁食后的早期传毒行为细节。结果显示：禁食处理没有显著影响电势落差（potential drop,pd）数目及穿刺过程中出现的第一个pd波形前穿刺时间这两个重要指标,但禁食处理能引起pd波的两个亚波形pdⅡ-1和pdⅡ-2持续时间的显著减短。进一步分析未禁食棉蚜传毒作用与pd亚波形的关系,显示传毒可能与pdⅡ-2的持续时间相关（P＝0.06）。因此,pdⅡ-2的持续时间可能是与棉蚜传毒相关的一个行为指标。该研究还建立了新的高效而稳定的获毒方法---5pd获毒法,与传统的5min获毒法相比,获毒效率显著提高。     

Aphis craccivora settling behaviour and acquisition of cowpea aphid-borne mosaic virus in aphid-resistant cowpea lines

The settling behaviour of Aphis craccivora Koch, the vector of cowpea aphid-borne mosaic virus (CAMV) in cowpea, Vigna unguiculata (L.) Walp., on aphid-resistant, aphid-tolerant and aphid-susceptible cowpea lines was investigated. It was found that although apterae counts on the aphid-susceptible and aphid-tolerant lines were higher than on the aphid-resistant ones, apterae were more widely dispersed among the latter. Whereas there was a positive significant correlation between alatae numbers and incidence of CAMV in the aphid-susceptible and aphid-tolerant lines, this correlation was negative in the aphid-resistant ones. However, the incidence of CAMV was not significantly different from each other in all the lines. This indicated that aphid activity (e.g. wide dispersal) was more important in the spread of CAMV than the absolute number of viruliferous alatae, an effect which was manifested on the aphid-resistant lines.Aphids acquire CAMV more readily from aphid-susceptible and aphid-tolerant source plants than from aphid-resistant ones. The significance of this in relation to secondary spread of CAMV and the effect of noncolonising aphids are discussed.

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Le comportement d'atterissage d'Aphis craccivora et l'acquisition du virus de la mosaïque transmis par puceron chez les variétés de niébe résistantes au puceron

Résumé Le comportement d'atterissage d'Aphis craccivora, vecteur du virus de la mosaique transmis par puceron (CAMV) sur Vigna unguiculata, a été examiné sur des variétés résistantes, sensibles ou tolérantes aux pucerons. On a observé que bien que les dénombrements d'aptères sur variétés sensibles ou tolérantes aient été plus élevés que sur variétés résistantes, les aptères étaient plus largement dispersés sur ces dernières. Tandis qu'il y avait une corrélation positive significative entre les nombres d'ailés et la présence de CAMV sur les variétés sensibles et tolérantes aux pucerons, cette corrélation était négative sur les variétés résistantes. Cependant, la fréquence de CAMV n'était pas significativement différente parmi toutes ces variétés. Ceci a montré l'activité des pucerons (c'est à dire leur dispersion) étail plus importante dans la diffusion du CAMV que le nombre absolu d'ailés virosés, effet qui était manifeste sur les variétés résistantes aux pucerons.Les pucerons contaminés au CAMV le sont plus par des plantes sensibles ou tolérantes aux pucerons que par des plantes résistantes. La discussion porte sur la signification de ceci en relation avec la diffusion secondaire de CAMV, et de l'effet des pucerons non colonisateurs.

     

The effect of Pymetrozine, a feeding inhibitor of Homoptera, in preventing transmission of cauliflower mosaic caulimovirus by the aphid species Myzus persicae (Sulzer)

Mature turnip plants, mechanically infected as seedlings with the semi-persistent, aphid transmitted caulimovirus, cauliflower mosaic (CaMV), were treated by spraying with either a solution of Pymetrozine plus adjuvant oil, adjuvant oil or water only. At the same time turnip seedlings were sprayed for each of the three treatments. Two h after spraying, Myzus persicae were caged onto an infected turnip plant for each of the three treatments. Twenty four h later, groups of 20 aphids were transferred from the infected plants, to seedlings from each of the three treatments. After 24 h, these were removed and seedlings were later recorded for infection. This acquisition/transmission assay was repeated at 3, 7, 14 and 21 days from treatment. Only aphids exposed to the Pymetrozine treated source plants were shown to move off the plant and failed to transmit CaMV effectively to treated or control seedlings during the 0 and 3 day assays. The majority soon died when transferred to test seedlings. Progressively, more aphids were found to survive and transmit CaMV during the 7 day and 14 day assays. By 21 days no significant effect could be recorded between treatments and controls. Aphids transferred from control treated source plants to Pymetrozine treated seedlings were able to transmit CaMV within all the assays, although higher mortality was recorded in the day 0 assessment when compared to those transferred to control treated seedlings. We conclude from this trial, that a single foliar treatment of 100 mg litre¹ Pymetrozine to CaMV infected turnip plants, effectively reduces the vectoring capability of M. persicae, that feed on these plants, for up to 7 days. However, Pymetrozine failed to stop virus transmission to treated seedlings from the ingress of viruliferous aphids. Pymetrozine was not shown to cause any phytotoxic responses to plants used in this trial.     

The effect of plant age and infection with virus yellows on the survival of Myzus persicae on sugar beet

Survival of Myzus persicae confined in clip-cages on mature leaves of sugar beet declined as the plants aged. Death of aphids was often preceded by the appearance of a black deposit in the aphids' stomachs, which may have been the cause of death. Both the rate of death and the proportion of aphids dying with black deposits was significantly less when plants were infected with beet yellows virus or beet mild yellowing virus, by comparison with healthy plants. The implication of these phenomena on the onset of mature plant resistance is discussed.     

Aphid Transmission of Potato aucuba mosaic virus Strains Mediated by Different Strains of Potato virus Y

Three British strains of potato aucuba mosaic virus (PAMV) were tested for transmissibility by the aphid Myzus persicae. None was aphid transmissible on its own but all three were transmitted in the nonpersistent manner by aphids that had previously been fed on a source of the potyvirus potato virus Y (PVY). Different PVY strains mediated PAMV transmission from Nicotiana clevelandii to Capsicum annuum to different degrees, and different PAMV strains were transmitted at different frequencies when assisted by the same PVY strain. These results are compatible with the idea that subtle differences in the PAMV coat protein and in the PVY helper component are responsible for diffrences in frequencies of transmission of PAMV, without however, excluding the possibility of effects of other undefined factors. Transmission of PAMV was no less frequent when mediated by a PVY strain that was unable to infect C. annuum than when a C. annuum‐infecting PVY strain was used.     

Homology between the proteins encoded by tobacco mosaic virus and two tricornaviruses

Summary A comparison was made of the amino acid sequences of the proteins encoded by RNAs 1 and 2 of alfalfa mosaic virus (A1MV) and brome mosaic virus (BMV), and the 126K and 183K proteins encoded by tobacco mosaic virus (TMV). Three blocks of extensive homology of about 200 to 350 amino acids each were observed. Two of these blocks are located in the A1MV and BMV RNA 1 encoded proteins and the TMV encoded 126K protein; they are situated at the N-terminus and C-terminus, respectively. The third block is located in the A1MV and BMV RNA 2 encoded proteins and the C-terminal part of the TMV encoded 183K protein. These homologies are discussed with respect to the functional equivalence of these putative replicase proteins and a possible evolutionary connection between A1MV, BMV and TMV.     

Azadirachta indica metabolites interfere with the host-endosymbiont relationship and inhibit the transmission of potato leafroll virus by Myzus persicae

The effects of neem (Azadirachta indica A. Juss) seed kernel extracts (NSKE) and azadirachtin on the ability of Myzus persicae (Sulz.) to transmit potato leafroll luteovirus (PLRV) was studied. Moreover, it was investigated whether treatments with these compounds would exert an effect on larval growth and mortality, and on the aphid intracellular symbionts. Endosymbiotic bacteria play an essential role in the performance of aphids, and in luteovirus transmission by aphids. NSKE and azadirachtin were offered to one-day-old M. persicae nymphs via a membrane feeding system. The neem metabolites displayed a 100% mortality at doses higher than 2560 ppm. At intermediate doses, ranging between 320 and 2560 ppm, larval growth and mortality were affected in a dose-dependent manner. The transmission of PLRV by M. persicae was inhibited by 55–90%. The endosymbiont population of the aphid was clearly affected by a treatment with neem metabolites as the release of their most abundant protein, Buchnera GroEL, into the haemocoel of the aphid was inhibited. Moreover, morphological aberrations on the bacterial endosymbionts were observed in aphids which fed on 2560 ppm of azadirachtin. At doses lower than 160 ppm of NSKE or azadirachtin, the endosymbiont population of M. persicae, and mortality, growth and feeding behaviour were similar to that of the untreated groups of aphids. However, PLRV transmission was still inhibited by 40–70%. The possible targets of the neem metabolites in the aphid are discussed.     

Transmission of potato leafroll virus in relation to the honeydew excretion of Myzus persicae

Honeydew excretion of single Myzus persicae nymphs on potato leafroll virus (PLVR)-infected Physalis floridana was studied during the acquisition access period (AAP) in relation to the efficiency of virus transmission.
With increasing length of the AAP, the percentage of nymphs that transmitted the virus increased. These nymphs produced significantly more honeydew droplets during the AAP on PLRV-infected P. floridana plants than nymphs which failed to transmit the virus. However, the number of honeydew droplets excreted during the AAP by transmitting nymphs did not affect the length of the latency period. Nymphs which infected the first test plant after a short latency period produced a similar amount of honeydew during the AAP to those with a longer latency period.
Honeydew excretion recorded on plants of varied age, showed that nymphs feeding on bottom leaves of infected plants produced more honeydew droplets than on comparable leaves of healthy plants. On infected plants, nymphs produced more honeydew droplets on bottom leaves with pronounced symptoms than on top leaves that hardly showed any symptom of PLRV infection.
The concentration of viral antigen measured by ELISA was lower in top leaves than in bottom leaves of infected plants. Nevertheless, nymphs feeding on top leaves transmitted the virus more efficiently than those which used bottom leaves as virus source. When bottom leaves were used as a virus source, the percentage of viruliferous nymphs decreased with plant age. These results indicate that the availability of virus for acquisition by aphids declines with increasing plant age and symptom severity.     

Detection of the luteoviruses, beet mild yellowing virus and beet western yellows virus, in aphids caught in sugar-beet and oilseed rape crops, 1990–1993

The incidence of beet mild yellowing luteovirus (BMYV) and non-beet-infecting strains of beet western yellows luteovirus (BWYV) in individual winged aphids, caught in yellow water-traps, in sugar beet during the spring and early summer, and in oilseed rape plots in the autumn, was monitored using monoclonal antibodies in ELISA tests from 1990 to 1993. Between 0% and 8% of the Myzus persicae trapped in sugar beet each year carried BMYV, whereas 0% to 4% caught in oilseed rape in the autumn contained this virus. In 1990, 6.5% of Macrosiphum euphorbiae trapped in sugar beet contained BMYV, but in subsequent years less than 1% were carrying virus. Much higher proportions (26–67%) of the M. persicae tested from sugar beet contained BWYV, and similar proportions tested from oilseed rape (24–45%) also carried this virus in the autumn. In contrast only 3–19% of the M. euphorbiae caught in sugar beet contained BWYV, and none in oilseed rape. In 1991 and 1992 large numbers of Breuicoryne brassicae were caught in the plot of oilseed rape, of which over 50% contained BWYV; none were carrying BMYV. In transmission studies between 1990 and 1992, 1% and 27% of M. persicae transmitted BMYV and BWYV respectively to indicator plants; subsequent ELISA tests on the same aphids showed that 3% and 33% respectively contained the two viruses. One percent of M. euphorbiae transmitted BMYV, but none were found to contain BMYV using ELISA; 15% transmitted BWYV whilst only 5% were found to carry the virus. In 1992 and 1993 the incidence of BMYV-infection in the sugar-beet fields in which aphids had been trapped ranged from 1.2%, in a field which had received granular pesticide (aldicarb) at drilling plus three foliar aphicidal sprays, to 39.5% in a field which had received only one foliar spray. In 1992 in a sugar-beet crop which had received no aphicidal treatments, and where 2.8% of immigrant M. persicae and 2.5% of M. euphorbiae contained BMYV, 11.6% of plants developed BMYV infection. Lowest levels of infection were associated with the use of granular pesticides at drilling. In 1990, 80% of oilseed rape plants in a field plot were infested with a mean of seven wingless M. persicae per plant by mid-December; 37% of these plants were infected with BWYV. The studies show that M. persicae is the principal vector of BWYV, and large proportions of winged M. persicae carry the virus, in contrast to BMYV, which is consistent with the common occurrence of BWYV in brassica crops such as oilseed rape.     

Transmission of Zucchini yellow mosaic virus by Colonizing and Non-colonizing Aphids in Greece and New Aphid Species Vectors of the Virus

Nineteen aphid species were tested for their ability to transmit Zucchini yellow mosaic virus (ZYMV) from and to zucchini under laboratory conditions. Sixteen species were found to be new vectors of ZYMV (i.e. Aphis craccae, Aphis fabae, Aphis nerii, Aulacorthum solani, Brachycaudus cardui, Brevicoryne brassicae, Hyalopterus pruni complex, Hyperomyzus lactucae, Macrosiphoniella sanborni, Macrosiphum rosae, Metopolophium dirhodum, Myzus cerasi, Rhopalosiphum maidis, R. padi, Semiaphis dauci and Sipha maydis). Their transmission efficiency by a single aphid was low (0.1–4.2%). Myzus persicae was used as a control and was the most efficient vector (41.1%, one aphid per plant). Hayhurstia atriplicis, Myzus ascalonicus and Sitobion avenae did not transmit the virus. In four out of six new vectors assayed in arena tests for propensity estimation, propensity was higher than efficiency. Data from an experimental zucchini field in northern Greece revealed a high correlation between ZYMV spread and alatae of the vector species. The most abundant aphid vectors during 2 years experimentation were M. persicae, Aphis gossypii and Aphis spiraecola. The possible role of the 16 new and the previously known aphid vectors in the epidemiology of ZYMV was investigated using data of transmission efficiency combined with the captures of their alatae in the Greek net of a Rothamsted type suction trap.     

桃蚜虫霉病始发期的初始感染与接触传染

自2002年10月至2005年5月在杭州上空诱获桃蚜(Myzus persicae)的迁飞性有翅蚜2351头,将其带回室内在(21±1)℃和12L∶12D条件下单头饲养12d,其中639头在定殖后7d内发病死亡,初始感染率达27·2%。在病死有翅蚜中,99·4%系5种蚜科专化性虫霉侵染所致,新蚜虫疠霉(Pandora neoaphidis)的发生比例高达81·4%。带病迁飞的有翅蚜在发病死亡前具有一定生殖力,定殖后第6天平均累计产若蚜(2·4±0·13)头,远低于同期未带病有翅蚜产下的(11·6±0·33)头。在带病有翅蚜建立的后代蚜群中,接触传染在母蚜死亡2d后即可见到。在定殖后第12天,二级感染占总观察蚜群数的13·3%,三级感染占总观察蚜群数的4·4%,占二级感染蚜群数的33·3%。此时,未带病有翅蚜的后代蚜群的平均活蚜数达(50·6±2·30)头,而带病有翅蚜的后代蚜群平均仅有(21·5±1·98)头。结果表明,虫霉病能够通过寄主带病迁飞传至寄主迁入地,并在后代蚜群中相互传染而起到调节蚜虫数量增长的作用。     

Transmission of Pepino mosaic virus by the Fungal Vector Olpidium virulentus

Transmission of Pepino mosaic virus (PepMV) by the fungal vector Olpidium virulentus was studied in two experiments. Two characterized cultures of the fungus were used as stock cultures for the assay: culture A was from lettuce roots collected in Castellón (Spain), and culture B was from tomato roots collected in Murcia (Spain). These fungal cultures were maintained in their original host and irrigated with sterile water. The drainage water collected from irrigating these stock cultures was used for watering PepMV‐infected and non‐infected tomato plants to constitute the acquisition–source plants of the assay, which were divided into six different plots: plants containing fungal culture A (non‐infected and PepMV‐infected); plants containing fungal culture B (non‐infected and PepMV‐infected); PepMV‐infected plants without the fungus; and plants non‐infected either with PepMV and the fungus. Thirty‐six healthy plants grouped into six plots, which constituted the virus acquisition–transmission plants of the assay, were irrigated with different drainage waters obtained by watering the different plots of the acquisition–source plants. PepMV was only transmitted to plants irrigated with the drainage water collected from PepMV‐infected plants whose roots contained the fungal culture B from tomato with a transmission rate of 8%. No infection was detected in plants irrigated with the drainage water collected from plots with only a fungus or virus infection. Both the virus and fungus were detected in water samples collected from the drainage water of the acquisition–source plants of the assay. These transmission assays demonstrated the possibility of PepMV transmission by O. virulentus collected from tomato crops.     

Cauliflower mosaic virus protein P6-TAV plays a major role in alteration of aphid vector feeding behaviour but not performance on infected Arabidopsis

Emerging evidence suggests that viral infection modifies host plant traits that in turn alter behaviour and performance of vectors colonizing the plants in a way conducive for transmission of both nonpersistent and persistent viruses. Similar evidence for semipersistent viruses like cauliflower mosaic virus (CaMV) is scarce. Here we compared the effects of Arabidopsis infection with mild (CM) and severe (JI) CaMV isolates on the feeding behaviour (recorded by the electrical penetration graph technique) and fecundity of the aphid vector Myzus persicae. Compared to mock-inoculated plants, feeding behaviour was altered similarly on CM- and JI-infected plants, but only aphids on JI-infected plants had reduced fecundity. To evaluate the role of the multifunctional CaMV protein P6-TAV, aphid feeding behaviour and fecundity were tested on transgenic Arabidopsis plants expressing wild-type (wt) and mutant versions of P6-TAV. In contrast to viral infection, aphid fecundity was unchanged on all transgenic lines, suggesting that other viral factors compromise fecundity. Aphid feeding behaviour was modified on wt P6-CM-, but not on wt P6-JI-expressing plants. Analysis of plants expressing P6 mutants identified N-terminal P6 domains contributing to modification of feeding behaviour. Taken together, we show that CaMV infection can modify both aphid fecundity and feeding behaviour and that P6 is only involved in the latter.     

Biochemical and physiological mechanisms underlying effects of Cucumber mosaic virus on host‐plant traits that mediate transmission by aphid vectors

The transmission of insect‐vectored diseases entails complex interactions among pathogens, hosts and vectors. Chemistry plays a key role in these interactions; yet, little work has addressed the chemical ecology of insect‐vectored diseases, especially in plant pathosystems. Recently, we documented effects of Cucumber mosaic virus (CMV) on the phenotype of its host (Cucurbita pepo) that influence plant‐aphid interactions and appear conducive to the non‐persistent transmission of this virus. CMV reduces host‐plant quality for aphids, causing rapid vector dispersal. Nevertheless, aphids are attracted to the elevated volatile emissions of CMV‐infected plants. Here, we show that CMV infection (1) disrupts levels of carbohydrates and amino acids in leaf tissue (where aphids initially probe plants and acquire virions) and in the phloem (where long‐term feeding occurs) in ways that reduce plant quality for aphids; (2) causes constitutive up‐regulation of salicylic acid; (3) alters herbivore‐induced jasmonic acid biosynthesis as well as the sensitivity of downstream defences to jasmonic acid; and (4) elevates ethylene emissions and free fatty acid precursors of volatiles. These findings are consistent with previously documented patterns of aphid performance and behaviour and provide a foundation for further exploration of the genetic mechanisms responsible for these effects and the evolutionary processes that shape them.     

Identification of Rubus yellow net virus as a distinct badnavirus and its detection by PCR in Rubus species and in aphids

Rubus yellow net virus (RYNV) infects Rubus species and cultivars worldwide and is an essential component of raspberry veinbanding mosaic (RVBMD), a virus disease complex that causes serious decline in plant vigour and productivity. The virus is transmitted, probably in a semi‐persistent manner, by the large raspberry aphid, Amphorophora idaei in Europe, and A. agathonica in North America. The particles of RYNV are bacilliform in shape and measure 80–150 × 25–30 nm, similar to those of badnaviruses. A1.7 kb fragment of the viral DNA was amplified by PCR and then directly sequenced. Analysis of this sequence suggests that RYNV is possibly a distinct species in the genus Badnavirus and is most closely related to Gooseberry vein banding associated virus (GVBAV) and Spiraea yellow leaf spot virus, two other badnaviruses described recently. Using the sequence derived from the PCR‐amplified viral DNA fragment, RYNV‐specific primers were designed and used in PCR to assay for RYNV in a range of Rubus germplasm infected with RYNV, with other unrelated viruses and virus‐like diseases found in Rubus, and in healthy plants. RYNV was detected in all glasshouse cultures of RYNV‐infected plants, whether alone or in complex infections with other viruses, but not from healthy Rubus plants, nor from plants infected with other viruses. It was also detected in field‐grown raspberry plants with and without symptoms of RVBMD and in raspberry plants infected with RYNV by viruliferous A. idaei. RYNV was also detected by PCR in A. idaei following access feeds on RYNV‐infected plants of 1 h or more. PCR failed to amplify DNA from gooseberry infected with GVBAV confirming the specificity of the RYNV analysis. PCR detection of RYNV in dormant raspberry buds allows assays to be made outside the natural growing season, providing a useful application for plant introduction and quarantine programmes.