Host range and some properties of groundnut rosette virus

Two isolates of groundnut rosette virus from East Africa (GRVE₁ and GRVE₂) and from West Africa (GRVW₁ and GRVW₂) were transmitted by Aphis craccivora obtained from West Africa. A third isolate from West Africa (GRVW₃) was not transmitted by A. craccivora from three widely separated sources. GRVW₁, GRVW₂ and GRVW₃ caused leaf-symptoms in groundnut of a mosaic pattern in light and dark green. GRVE₁ and GRVE₂ caused chlorosis or chlorosis and leaf distortion as well as mosaic symptoms. Groundnut plants with GRVW₁ could not be infected by means of aphids with GRVE₁, and GRVE₁ gave similar protection against GRVW₁, which suggests that they are strains of the same virus. All isolates were transmissible manually from groundnut to groundnut (Arachis hypogea), Trifolium incarnatum and T. repens, and caused systemic infection. Inoculated Nicotiana clevelandii and N. rustica developed symptoms but virus could not be recovered from them. Chenopodium amaranticolor, C. hybridum and C. quinoa showed local lesions on inoculated leaves. Virus could be acquired by aphids from groundnut or Trifolium repens infected by means of aphids, but not from those infected by manual inoculation. Virus could not be recovered from T. incarnatum manually or by aphids, but was transmitted by cleft-grafting from clover to groundnut. Saps extracted in borax buffer plus zinc sulphate at pH 9 from plants infected with GRVW₁ and GRVE₁ remained infective at 18° C. for 1 week, and at — 20° C. for up to 4 weeks. Virus could be recovered from frozen leaves. Buffered saps lost infectivity when heated above 50° C. for 10 min.; most were still infective when diluted 1/10 and some at 1/100. Electron micrographs of partially purified preparations contained spherical particles 25–28 mμ in diameter. There were usually only about five per microscope field and they resembled those of some other viruses.     

Viruses associated with chlorotic rosette and green rosette diseases of groundnut in Nigeria*

Groundnut (Arachis hypogaea) plants from Nigeria with chlorotic rosette disease contained a manually transmissible virus, considered to be a strain of groundnut rosette virus (GRV(C)). GRV(C) infected nine out of 32 species in three out of nine families. It caused local lesions without systemic infection in Chenopodium amaranticolor, C. murale and C. quinoa, and systemic symptoms in Glycine max, Nicotiana benthamiana, N. clevelandii and Phaseolus vulgaris as well as in groundnut. Some ‘rosette-resistant’ groundnut lines were also infected. GRV(C) was transmitted by Aphis craccivora, but only from groundnut plants that were also infected with an aphid-transmissible second virus, which was not manually transmissible and was considered to be groundnut rosette assistor virus (GRAV). Plants infected with GRAV contained isometric particles c. 25 nm in diameter which were detectable by immunosorbent electron microscopy on grids coated with antisera to several luteoviruses, especially with antisera to bean leaf roll, potato leafroll and beet western yellows viruses. No virus-like particles were observed in extracts from plants infected with GRV(C) alone. A single groundnut plant obtained from Nigeria with symptoms of green rosette contained luteovirus particles, presumed to be of GRAV, and yielded a manually transmissible virus that induced symptoms similar to those of GRV(C) in C. amaranticolor but gave only mild or symptomless infection of N. benthamiana and N. clevelandii. It was considered to be a strain of GRV and designated GRV(G).     

Groundnut eyespot virus, a new member of the potyvirus group

A virus causing ‘eyespot’ leaf symptoms in groundnut plants was transmitted by sap-inoculation and by Aphis craccivora in the non-persistent manner. It infected 16 of 72 species from five of 12 families and was easily propagated in Arachis hypogaea and Physalis floridana. The virus has particles c. 13 × 755 nm and is serologically closely related to soybean mosaic and pepper veinal mottle viruses, and more distantly to four other potyviruses. The virus differs in host range, in vitro properties and serological properties from previously described strains of soybean mosaic and pepper veinal mottle viruses. It seems to be a distinct member of the potyvirus group and we propose the name groundnut eyespot virus.     

The Ability of Aphis craccivora, A. gossypii and A. citricola to Transmit Single and Mixed Viruses to Cowpeas

The ability of populations of adult apterous Aphis craccivora, A. gossypii and A. citricola to transmit the cowpea aphid-borne virus (CAMV) and cucumber mosaic virus (CMV) to cowpea was investigated. CMV was more readily transmitted than CAMV by all three aphid species, but was most readily transmitted by A. craccivora and A. citricola, with transmissions ranging from 64–71 %. With CAMV, the infection level with A. gossypii was higher than with A. craccivora and both were more efficient than A. citricola, although the differences were not significant. With mixed infections of CAMV and CMV, there was a higher level of CAMV transmission using A. craccivora from sequential feeding when CMV-infected plants were fed on first followed by CAMV-infected plants, suggesting that cowpea plants were more prone to infection by CAMV when already infected by CMV.     

Aphid-injection experiments with carrot mottle virus and its helper virus, carrot red leaf

Carrot mottle virus (CMotV) and its helper virus, carrot red leaf (CRLV), were not transmitted by aphids (Cavariella aegopodii) that had fed through membranes on, or had been injected with, sap from mixedly infected chervil plants or partially purified preparations of CMotV. However, the viruses were transmitted by recipient aphids injected with haemolymph from donor aphids that had fed on mixedly infected plants but not by a second series of recipients injected with haemolymph from the first series. Some of the first series of recipients transmitted both viruses for up to 11 days but others transmitted erratically and many lost ability to transmit after a few days. The results confirm that both viruses are circulative but provide no evidence for multiplication in the vector. Non-viruliferous aphids, or aphids that had acquired CRLV by feeding, did not transmit CMotV when they were injected with haemolymph from aphids that had fed on a source of CMotV alone, confirming that they can only transmit CMotV when they acquire it from a mixedly infected plant. When extracts from donor aphids were treated with ether before injection, recipient aphids transmitted both CRLV and CMotV, although the infectivity of CMotV grown in Nicotiana clevelandii in the absence of CRLV is destroyed by ether treatment. CMotV particles acquired by aphids from mixedly infected plants therefore differed in some way from those in singly infected plants. A plausible explanation of these results, and of the dependence of CMotV on CRLV for aphid transmission, is that doubly infected plants contain some particles that consist of CMotV nucleic acid coated with CRLV protein.     

TRANSMISSION OF GROUNDNUT ROSETTE VIRUS

The rosette virus was transmitted to groundnut plants, if previously etiolated, bymechanical inoculation of juice with 'Celite' addition; but only a small proportion of the inoculations succeeded.
Aphis craccivora (Koch), the known vector, transmitted the virus by feeding on germinating groundnut seeds; and from this fact we developed an experimental technique that is convenient and flexible.
Different races of this species appeared to vary in inherent efficiency in transmission, and one failed ever to transmit. Within races that could transmit, all larval forms and alate and apterous adults might transmit; but alatae were sometimes significantly more efficient than apterae, and at other times the converse held. A field experiment showed that wingless forms, moving over the soil surface, might play a predominant part in secondary spread around a rosetted plant.
Comparative tests with groups of I, 2, 3 and 4 infective aphids supported the hypothesis that infections by this vector are individual and independent.
Single aphids, tested for 24 hr. on 10 successive days without access to an outside source of virus, might infect on any day up to the tenth. Similar results were obtained in a succession of I hr. tests on a single day. In the infected seed the virus rapidly became available to feeding aphids; previously non-infective aphids acquired the virus by feeding on a seed during the third day from the first exposure of this seed to infective aphids.     

Groundnut rosette and its assistor virus

Chlorotic rosette from Malawi (isolate CR1), passed through Stylosanthes gracilis and S. juncea, was not subsequently transmissible from groundnuts (Arachis hypogaea) by Aphis craccivora or A. gossypii, but with S. mucronata transmissibility was occasionally regained after a period of time. Aphid transmissibility was similarly lost after passage of two isolates (a chlorotic rosette from Rhodesia, CR2, and a green rosette from Nigeria, GR) through soybean (Soja max) and after manual inoculation to groundnuts. Groundnut plants that remained symptomless after exposure to rosette infection by aphids often contained a virus that restored aphid transmissibility when introduced into groundnuts containing the vectorless virus from that isolate. Groundnut rosette disease therefore consists of a symptom-inducing virus that we call groundnut rosette virus (GRV) and a symptomless assistor virus (GRAV) that must be present for aphid transmission. The interactions between the GRV and GRAV of chlorotic and green rosette, and their transmission by different vector races, are described.     

SOME FACTORS AFFECTING THE TRANSMISSION OF LEAF-ROLL VIRUS BY APHIDS

Datura tatula is a more suitable host than potato for studying the factors influencing the transmission of potato leaf-roll virus by Myzus persicae ; it is more easily infected, provides a better source of virus for feeding aphids, produces symptoms more quickly and over a longer period of the year.
Loughnane's (1943) claim that leaf-roll virus is transmitted by starved aphids that feed for only 5 min. on infected potato plants was not confirmed. The shortest infection-feeding time in which M. persicae aphids became infective was 2 hr.; such aphids did not infect healthy plants in the first 2 days and, when transferred to a series of healthy plants at intervals, infected only few. The ability to cause infections was increased by increasing the length of infection feeding. Aphids fed for many days on infected plants could infect healthy plants in the first 15 min. of test feeding, and they continued to cause infections for long periods.
Aphids became infective more readily when feeding on recently infected Datura tatula , showing only slight symptoms, than on older plants with pronounced chlorosis; similarly, young potato sprouts showing no symptoms were better sources of virus for aphids than older plants showing severe leaf roll.
The differences in severity of symptoms shown by potato plants with leaf roll in the field mainly occur because of differences in virulence of accompanying strains of potato virus X , but isolates of leaf-roll virus were found that also varied in virulence.     

Tobacco yellow vein,a virus dependent on assistor viruses for its transmission by aphids*

Tobacco yellow vein, a disease found in Malawi, is caused by a combination of two viruses transmitted in the persistent manner by aphids. One component, tobacco yellow vein virus (TYVV) is manually transmissible, but aphids transmit it only from plants also containing the other (assistor) component, which is not manually transmissible. Aphids also transmit TYVV from plants containing either of two other assistor viruses - tobacco vein-distorting and groundnut rosette assistor. A virulent isolate of TYVV infected Soja max, Arachis hypogaea and several solanaceous species. It infected plants already containing tobacco mottle or groundnut rosette viruses but not those containing a mild isolate of TYVV.     

Cucurbit aphid‐borne yellows virus (CABYV) modifies the alighting,settling and probing behaviour of its vector Aphis gossypii favouring its own spread

Plant pathogens are able to influence the behaviour and fitness of their vectors in such a way that changes in plant–pathogen–vector interactions can affect their transmission. Such influence can be direct or indirect, depending on whether it is mediated by the presence of the pathogen in the vector's body or by host changes as a consequence of pathogen infection. We report the effect that the persistently aphid‐transmitted Cucurbit aphid‐borne yellows virus (CABYV, Polerovirus) can induce on the alighting, settling and probing behaviour activities of its vector, the cotton aphid Aphis gossypii. Only minor direct changes on aphid feeding behaviour were observed when viruliferous aphids fed on non‐infected plants. However, the feeding behaviour of non‐viruliferous aphids was very different on CABYV‐infected than on non‐infected plants. Non‐viruliferous aphids spent longer time feeding from the phloem in CABYV‐infected plants compared to non‐infected plants, suggesting that CABYV indirectly manipulates aphid feeding behaviour through its shared host plant in order to favour viral acquisition. Viruliferous aphids showed a clear preference for non‐infected over CABYV‐infected plants at short and long time, while such behaviour was not observed for non‐viruliferous aphids. Overall, our results indicate that CABYV induces changes in its host plant that modifies aphid feeding behaviour in a way that virus acquisition from infected plants is enhanced. Once the aphids become viruliferous they prefer to settle on healthy plants, leading to optimise the transmission and spread of this phloem‐limited virus.     

Effect of Fungicides on the Viability of Phylophthora cactorum Propagules m the Soil

Vein-clearing followed by downward rolling and necrosis of leaves and severe stunting of groundnut (Arachis hypogaea) plants were caused by cowpea mild mottle virus (CMMV). The virus was readily transmitted by mechanical sap inoculations to groundnut and to 10 plant species belonging to Leguminosae, Chenopodiaceae and Solanaceae. Chenopodium quinoa and Beta vulgaris were good diagnostic hosts. Diseased sap remained infective at 10^–3 but not 10^–4, when stored 8 to 9 days at 25 °C; for 10min at 75 °C but not 80°C. In limited tests, virus was not seed-transmitted m groundnut or soybean. Virus was transmitted by Bemisia tabaci but not by Aphis craccivora or Myzus persicae. An antiserum for CMMV was produced and virus was serologically related to CMMV reported on cowpea and groundnut crinkle virus (GCV) from West Africa. Employing carbon diffraction grating replica as a standard the modal length of virus particles to be 610 nm. Infected cells contained large number of virus particles associated with endoplasmic reticulum.     

Effect of sowing date on incidence of Sudanese broad bean mosaic virus in, and yield of, Viciafaba

Delaying the sowing of irrigated field beans in the Sudan after October greatly lowered the yield of seed, and increased both infestation by aphids and the incidence of Sudanese broad bean mosaic virus (SBBMV). Yield per plant was positively correlated with number of pods, but negatively with percentage infection with SBBMV. In greenhouse conditions, SBBMV was readily acquired from diseased plants and inoculated to healthy plants in 5 min feeding periods by both Aphis craccivora and Acyrthosiphon sesbaniae.     

STUDIES ON TWO APHID-TRANSMITTED VIRUSES OF LEGUMINOUS CROPS

Pea mosaic virus was transmitted by Myzus persicae Sulz., Macrosiphum pisi Kalt., M. solanifolii Ash. and Aphis fabae Scop., but not by Hyperomyzus staphyleae Koch. It is a 'non-persistent' virus (Watson & Roberts, 1939), and is most readily transmitted when vectors are fasted and then given a short infection feeding. Vector efficiency was not increased by increases in preliminary fasting beyond 15 min. or with increasing infection feeding beyond 1 hr. Most aphids became non-infective within 15 min. when feeding, but fasting aphids remained infective for 3 hr. Species that fed readily on the infected plants were less efficient vectors than those which did not. Seed set by infected plants produced healthy seedlings.
Pea enation mosaic virus persisted in Myzus persicae and Macrosiphum pisi for more than 140 hr.; its transmission was unaffected by preliminary treatments of aphids. No transmission was obtained until at least 4 hr. after aphids had left infected plants; usually the 'latent' period exceeded 1 day and its duration was apparently unaffected by the length of the infection feeding.     

Infection of potato plants with potato leafroll virus changes attraction and feeding behaviour of Myzus persicae

Potato leafroll virus (PLRV; genus Polerovirus, family Luteoviridae) is a persistently transmitted circulative virus that depends on aphids for spreading. The primary vector of PLRV is the aphid Myzus persicae (Sulzer) (Homoptera: Aphididae). Solanum tuberosum L. potato cv. Kardal (Solanaceae) has a certain degree of resistance to M. persicae: young leaves seem to be resistant, whereas senescent leaves are susceptible. In this study, we investigated whether PLRV‐infection of potato plants affected aphid behaviour. We found that M. persicae's ability to differentiate headspace volatiles emitted from PLRV‐infected and non‐infected potato plants depends on the age of the leaf. In young apical leaves, no difference in aphid attraction was found between PLRV‐infected and non‐infected leaves. In fact, hardly any aphids were attracted. On the contrary, in mature leaves, headspace volatiles from virus infected leaves attracted the aphids. We also studied the effect of PLRV‐infection on probing and feeding behaviour (plant penetration) of M. persicae using the electrical penetration graph technique (DC system). Several differences were observed between plant penetration in PLRV‐infected and non‐infected plants, but only after infected plants showed visual symptoms of PLRV infection. The effects of PLRV‐infection in plants on the behaviour of M. persicae, the vector of the virus, and the implications of these effects on the transmission of the virus are thoroughly discussed.     

Transmission of broad bean stain virus and Echtes Ackerbohnenmosaik-Virus to field beans (Viciajaba) by weevils

Sitona lineatus and Apion vorax were the two most common species of weevil on field beans (Vicia faba minor) at Rothamsted between 1970 and 1974. In glasshouse tests, A. vorax was a much more efficient vector than 5. lineatus of broad bean stain virus (BBSV) and Echtes Ackerbohnenmosaik-Virus (EAMV), and both species transmitted EAMV more often than BBSV. Five other species of Apion transmitted the viruses infrequently or not at all. S. lineatus adults transmitted no more often after 8–16 days on infected plants than after 1–2 days. Some A. vorax adults transmitted EAMV, but not BBSV, after feeding on infected leaves for a few minutes. After 4 days on infected plants, A. vorax sometimes remained infective for the following 8 days. No A. vorax collected from woodland plants in spring was infective with BBSV or EAMV, but 4% from bean crops containing seed-borne infection carried BBSV and 17% carried EAMV. BBSV and EAMV were recovered from triturated weevils, but not from weevil haemolymph. Possibly the viruses are transmitted as contaminants of the mouthparts or by regurgitation during feeding, but A. vorax was observed to regurgitate only when anaesthetized. BBSV and EAMV were not transmitted by aphids (Aphis fabae and Acyrthosiphon pisum), nor by pollen beetles {Meligethes spp.). Field observations suggest that infected seed is the main source of BBSV and EAMV in spring-sown crops, and that crops grown from virus-free seed, and isolated from infected crops by 250–500 m, remain free of infection for most of the season.     

Studies on the Relationship of Urdbean Leaf Crinkle Virus and its Vectors, Aphis craccivora and Acyrthosiphon pisum

Pre and Post-virus-acquisition starvation of Aphis craccivora Koch, and Acyrthosiphon pisum Harris resulted in appreciable increase in percentage of transmission of urdbean leaf crinkle virus. Highest transmission occured when aphids were starved for 90 min prior to virus-acquisition. A. pisum and A. craccivora on 20 and 80 min of post-acquisition starvation and 10 and 20 min of virus-acquisition, respectively inoculated more number of plants. Both the aphids transmitted the virus in probes lasting for one min. However, beyond 5 min of successive transfer on test plants loss in transmissibility was apparent. Viruliferous aphid off the plant retained the virus for a much longer period than on maize plant. The virus appears to be non-persistently borne in the aphids.     

Properties and partial purification of infective material from plants containing groundnut rosette virus*

Groundnut plants with chlorotic rosette disease contain a manually transmissible virus, groundnut rosette (GRV), which is also transmitted in the persistent (circulative) manner by aphids (Aphis craccivora), but only from plants that are co-infected with a manually non-transmissible luteovirus, groundnut rosette assistor virus (GRAV). Strains of GRV from plants with chlorotic or green forms of rosette are called GRV(C) and GRV(G) respectively. An isolate of GRV(C) from Nigeria remained infective in Nicotiana clevelandii leaf extracts for 1 day at room temperature and for 15 days at 4d?C, but lost infectivity after 1 day at -20d?C or after dilution to 10^--⁴. Its infectivity and longevity in vitro were not altered by addition of 1 mg/litre bentonite to the extraction buffer. Infectivity in leaf extracts was abolished by treatment with 50% (v/v) ether, 10% (v/v) chloroform or 8% (v/v) n-butanol, but not by treatment for 30 min with RNase A at up to 100 ng/ml. In attempts to purify GRV(C), nearly all the infectivity from N. clevelandii extracts was found in the pellets from centrifugation at 65 000 g for 1. 5 h; infectivity also occurred in a cell membrane fraction that collected at the top of a 30% sucrose ‘cushion’ containing 4% polyethylene glycol and 0.2 M NaCI. However, no virus-like particles were found in either type of preparation by electron microscopy. Nucleic acid preparations made directly from GRV(C)-infected N. clevelandii leaves were very infective; this infectivity was totally inactivated by treatment for 30 min with RNase A at 10 ng/ml in buffers of both low and high ionic strength and was therefore attributed to ssRNA. When nucleic acid preparations were electrophoresed in gels no virus-specific bands were visible but the position of the infectivity indicated that the infective ssRNA has an apparent mol. wt of c. 1.55 × 10⁶. A similar mol. wt was indicated by the rate of sedimentation of the infective ssRNA in sucrose gradients. Preparations of dsRNA made from GRV(C)-infected N. clevelandii leaves contained a species of mol. wt c. 3.0 × 10⁶; in addition some dsRNA preparations contained an abundant component of mol. wt c. 0.6 × 106 together with several other components of intermediate mol. wt. Similar patterns of bands were observed in dsRNA preparations made from Nigerian-grown groundnut material infected with GRV(C) alone, or with GRV(C) + GRAV, or with GRV(G) + GRAV. The properties of GRV closely resemble those of two other viruses that depend on luteoviruses for transmission by aphids, carrot mottle virus and lettuce speckles mottle virus.     

Factors affecting aphid acquisition and transmission of soybean mosaic virus

Myzus persicae transmitted soybean mosaic virus (SMV) most efficiently following 30 or 60 s acquisition probes on infected plants. There were no differences in susceptibility to SMV infection of soybean plants 1 to 12 wk old, but symptoms were more severe in plants inoculated when young than when old. Soybeans inoculated between developmental stages R3 and R6 only showed yellowish-brown blotching on one or more leaves. There were no observable differences in the time of appearance or type of symptoms shown by soybean seedlings inoculated either by sap or by aphids; infected plants became acquisition hosts for aphids 5–6 days after inoculation. There was no change in the efficiency with which M. persicae transmitted SMV from source plants up to 18 wk after inoculation. M. persicae transmitted SMV from leaves of field-grown soybeans when plants were inoculated at developmental stages V6, R2, and R3 and tested as sources 57–74 days after inoculation but not from plants inoculated at R5 and tested as sources 14 to 32 days after inoculation. M. persicae acquired SMV from soybean buds, flowers, green bean pods, and unifoliolate, trifoliolate, and senescent leaves. Middle-aged and deformed leaves were better sources of the virus than buds, unfolding and old symptomless leaves. The results are being incorporated into a computer model of SMV epidemiology.     

Transmission characteristics and some other properties of bean yellow vein-banding virus, and its association with pea enation

Bean yellow vein-banding virus (BYVBV) has been found occasionally in mixed infection with pea enation mosaic virus (PEMV) in spring-sown field beans (Vicia faba minor) in southern England. Glasshouse tests confirmed that, like PEMV, BYVBV is transmissible by manual inoculation and by aphids in the persistent manner. However, BYVBV can be transmitted by aphids only from plants that are also infected with a helper virus, usually PEMV. Thus after separation from PEMV by passage through Phaseolus vulgaris it was no longer aphid-transmissible. It became aphid-transmissible again only after re-mixing in plants with PEMV or with a substitute helper, bean leaf roll virus (BLRV). It was not transmitted by aphids that fed sequentially on plants singly infected with PEMV and BYVBV. Thus the interaction between BYVBV and PEMV (or BLRV) that enables BYVBV to be transmitted by aphids seems to occur only in doubly infected plants. However, it was not transmitted by aphids from plants doubly infected with BYVBV and broad bean wilt virus (BBWV). BYVBV and PEMV were transmitted more readily by Acyrthosiphon pisum than by Myzus persicae; neither virus was transmitted by Aphis fabae. Phenol extracts of BYVBV-infected leaves were more infective than phosphate buffer or bentonite-clarified extracts and were sometimes infective when diluted to 1/1000. The infectivity of BYVBV in phosphate buffer extracts of leaves singly infected with BYVBV, unlike that in extracts of leaves doubly infected with BYVBV and PEMV (or BLRV), was destroyed by treatment with organic solvents. BYVBV infected 11 of 28 plant species that were inoculated with phenol extracts; seven of the infected species were legumes. No transmission of BYVBV was detected through seed harvested from infected field bean plants. Isometric particles c. 30 nm in diameter were seen in extracts of plants doubly infected with BYVBV and PEMV but not in extracts of plants infected with BYVBV alone. Leaves of plants infected with BYVBV, alone or with PEMV, contained membrane-bound structures c. 50–90 nm in diameter associated with the tonoplast in cell vacuoles. These structures were not found in healthy leaves. BYVBV has several properties in common with other known aphid-borne viruses that are helper-dependent and transmitted in a persistent manner. Possibly, as suggested for some of them, aphid transmission of BYVBV depends on the coating of its nucleic acid with helper virus coat protein.     

THE TRANSMISSION OF PLANT VIRUSES BY BITING INSECTS, WITH PARTICULAR REFERENCE TO COWPEA MOSAIC

Experiments on the virus-vector relationship of the Trinidad cowpea mosaic virus, transmitted by Ceratoma ruficornis , gave the following results: ability to infect decreased with increasing time after ceasing to feed on infected plants, but vectors remained infective for 14 days (much longer than the longevity in vitro of the virus at glasshouse shade temperatures of 23–31°C.); the beetles transmitted more consistently after longer feeding on infected plants, though feeds of under 5 min. made them efficient vectors; the proportion of plants infected increased with the amount of feeding damage on them; fasting the vectors before feeding on infected plants increased voracity but had no effect on their ability to transmit; beetles became infective immediately after feeding on infected plants. Cowpeas were infected by inoculation with macerated infective vectors or with juice regurgitated by vectors. There is no evidence that aphids or other sucking insects can transmit the virus. It seems similar to squash mosaic and turnip yellow mosaic, for vectors of all three viruses probably transmit by regurgitating infective juice during feeding.