Javesella Pellucida Research Articles

Nesting biology of Mimumesa littoralis (Bondroit, 1934) (Hymenoptera, Spheciformes) in Poland

The biology of Mimumesa littoralis was studied on sandy soil (Sierakowo) and wasteland with hard substrate (Kowalewo Pomorskie) in northern Poland. The study presents information on the bionomics of the rare digger wasp Mimumesa littoralis (Bondroit,1934). Females of Mimumesa littoralis nested both on sandy soil and wasteland with hard substrate. Their nests consisted of 2–3 cells. One cell contained up to 11 prey items belonging to species from five genera: Megadelphax spp., Dicranotropis hamata, Javesella spp., Laodelphax striatella, Javesella pellucida (Hemiptera: Delphacidae), and Streptanus sp. (Hemiptera: Cicadellidae), which had not been previously reported in the literature. The frequency with which the female brought prey to the nest varied from 12 to 21 min. In addition, the kleptoparasite Senotainia conica (Diptera: Sarcophagidae) was found in the nest. Adult individuals were observed feeding on the flowers of Pimpinella sp.

Can monophagous specialists mediate host plant choices in generalist planthoppers (Hemiptera: Delphacidae)?

A preference experiment was set up with two planthopper species (Hemiptera: Delphacidae) to test the influence of competition on host plant choice. The delphacid Javesella pellucida was chosen as a generalist and the rarer Ribautodelphax imitans as a monophagous specialist, which feeds on the grass, tall fescue Schedonorus arundinaceus. In the absence of the specialist, the generalist showed a marked preference for tall fescue. In some experiments, however, the introduction of the specialist resulted in a shift of preference to an alternative plant if the specialist was established prior to the introduction of the generalist. This experiment supports the hypothesis that specialist herbivores can potentially alter the host plant choices of generalists, which may lead to differing host plant use patterns in insect communities.

Sixty Years After the First Description: Genome Sequence and Biological Characterization of European Wheat Striate Mosaic Virus Infecting Cereal Crops.

High-throughput sequencing technologies were used to identify plant viruses in cereal samples surveyed from 2012 to 2017. Fifteen genome sequences of a tenuivirus infecting wheat, oats, and spelt in Estonia, Norway, and Sweden were identified and characterized by their distances to other tenuivirus sequences. Like most tenuiviruses, the genome of this tenuivirus contains four genomic segments. The isolates found from different countries shared at least 92% nucleotide sequence identity at the genome level. The planthopper Javesella pellucida was identified as a vector of the virus. Laboratory transmission tests using this vector indicated that wheat, oats, barley, rye, and triticale, but none of the tested pasture grass species (Alopecurus pratensis, Dactylis glomerata, Festuca rubra, Lolium multiflorum, Phleum pratense, and Poa pratensis), are susceptible. Taking into account the vector and host range data, the tenuivirus we have found most probably represents European wheat striate mosaic virus first identified about 60 years ago. Interestingly, whereas we were not able to infect any of the tested cereal species mechanically, Nicotiana benthamiana was infected via mechanical inoculation in laboratory conditions, displaying symptoms of yellow spots and vein clearing evolving into necrosis, eventually leading to plant death. Surprisingly, one of the virus genome segments (RNA2) encoding both a putative host systemic movement enhancer protein and a putative vector transmission factor was not detected in N. benthamiana after several passages even though systemic infection was observed, raising fundamental questions about the role of this segment in the systemic spread in several hosts.

Preliminary Research on the Wheat Pests and on Their Integrated Control during 2015-2016, at Agricultural Research-Development Station Turda

In Transylvania, the evolution of wheat insect pests is strongly influenced by the ecotehnological conditions, by climate change and current technology (Malschi, 2009 Malschi et al., 2015). The paper presents the dynamics and importance of the main pests of wheat (thrips, aphids, leafhoppers, wheat flies, cereals sunbugs, investigated under the integrated pest control system suitable of the area. During 2015-2016, the investigations were conducted at the Agricultural Research and Development Station Turda, from the wheat no tillage cultural system with cereal rotation of three years and applying all zonal recommendations of technology and phytosanitary complex. The pest monitoring was performed based on the samples collected with entomological net, by decadal 100 sweep-net catches/sample. The study data shows the danger of the attack of abundant populations of wheat flies (Phorbia securis, Delia coarctata, Opomyza florum, Oscinella frit etc.; wheat fleas (Chaetocnema aridula) and cereal leaf beetle (Oulema melanopa); leafhoppers (Psammotettix alienus, Javesella pellucida, Macrosteles laevis); aphids (Sitobion avenae, Schizaphis graminum, Rhopalosiphum padi); thrips (Haplothrips tritici), sunbugs (Eurygaster maura, Aelia acuminata) etc., and the necessity of applying insecticide treatments on the vegetation.Since 2015, a stronger impact of global warming on the wheat pests structure (%) are found. This change began on the last ten years. The importance of cereal sunbugs is increasing, well as the importance of the wheat flies, aphids and leafhoppers, which requires professional study on the pest dynamics and adequate integrated control of wheat pests.

Suction sampling of grassland invertebrates using the G-vac: Quantifying and avoiding peripheral suction effects

Suction sampling with modified garden leaf-blowers (G-vacs) is a widely used method for research on invertebrates in agricultural and grassland habitats. Approaches vary from sweeping the collecting nozzle across the surface of the vegetation within a known area, applying the nozzle firmly to the ground to delimit a sample area equal to nozzle crosssection, or applying the nozzle repeatedly within a larger open-ended cylinder placed on the ground. These approaches vary in potential for the inadvertent capture of specimens from outside of the sample area as a result of air being drawn into the nozzle from adjacent vegetation. This has never been studied adequately and is defined here for the first time as the Peripheral Suction Effect (PSE). Invertebrate species are likely to differ in susceptibility to PSE and so both sample size and composition could be impacted. This study compares two series of samples of Auchenorrhyncha taken using the same G-vac suction sampler (nozzle area, 0.01 m2) from areas enclosed and unenclosed by an openended cylindrical enclosure (area 0.17 m2) intended to prevent PSE. The unenclosed samples contained greater numbers of leafhoppers including Arthaldeus pascuellus, Javesella pellucida and immature Deltocephalinae. Numbers of immature Delphacinae did not differ between enclosed and unenclosed samples. The species composition of the two series of samples was similar, but the proportional representation of immature Delphacinae in unenclosed samples was diluted by the inflated numbers of other taxa that were drawn from the surrounding area. Peripheral suction effects are taxa-specific and therefore have the potential to bias measures of invertebrate community composition. Use of an open-ended cylinder to delimit the sample area is recommended as a simple, inexpensive and effective method of avoiding problems associated with PSE when using a G-vac. The potential for PSE with other models of suction samplers is discussed and questions for further research are identified.

New Entomocoenotic Particularities and Integrated Pest Control in Transylvanian Wheat Crops Under the Impact of Climate Warming

Based on the entomological research at the ARDS Turda, the paper presents new research on pest abundance in wheat crops in relation to the climate warming in Transylvania and the adequate integrated pest control methods under different cultural soil technologies: classical (ploughing) and conservative (no tillage), in open field and in agroforestry belts agroecosystems. During 2007-2014, the study has revealed data on species composition and dynamics. Species determination has been achieved based on the samples performed every 10 days , by 100 double sweep-net catches. Were pointed out major outbreaks of abundance of thrips ( Haplothrips tritici ), as eudominant species; of wheat flies (Chloropidae and Anthomyiidae); stem flea beetles ( Chaetocnema aridula ); leafhoppers ( Javesella pellucida, Psammotettix alienus etc.) and aphids ( Sitobion avenae etc. ), as dominant groups; cereal bugs ( Eurygaster maura, Aelia acuminata ); Coleoptera: Agriotes , Zabrus tenebrioides etc. Due to aridization and climate warming, the critical attack moments have been recorded 3-4 weeks earlier and overlapped.            IPM recommends special attention to preventing measures for flies, leafhoppers, aphids, etc., which shows a high biological potential: optimal sowing time, agrotechnical methods, seed treatment with systemic insecticide and complex plant protection measures. The results proved the importance of insecticide applications: at the end of tillering phase (13-33 DC stage) and at the flag-leaf appearance and ear emergence in 45-59 DC stage. At the first treatment, cereal flies, fleas, leafhoppers, thrips, bugs etc. are controlled simultaneously, by recommending the shock (pyrethroids) or systemic insecticides (neonicotinoid etc.). At the second treatment, the ear pests are controlled simultaneously and it is recommended the shock insecticides (pyrethroids etc.) with reduced effects on the useful entomophagous. The IPM is a major section of successive soil no tillage technologies, comprising a special pest control strategy, with insecticides application on seed treatment and in 2-3 successive treatments in vegetation. Entomophagous populations are particularly abundant in open field area, in classic and in soil no tillage technologies. In the farming system with protective agro-forestry belts–favorable for increasing of entomophags species, the research pointed out the efficiency of biological control, only using the entomophagous natural resources.

Structure of the ovaries and oogenesis in Cixius nervosus (Cixiidae), Javesella pellucida and Conomelus anceps (Delphacidae) (Insecta, Hemiptera, Fulgoromorpha)

Ovary organization in representatives of two families of Fulgoromorpha, Cixiidae ( Cixius nervosus) and Delphacidae ( Javesella pellucida and Conomelus anceps), was examined by light and transmission electron microscopy. Ovaries of studied fulgoromorphans consist of telotrophic ovarioles. From apex to base individual ovarioles have four well defined regions: a terminal filament, tropharium (trophic chamber), vitellarium and pedicel (ovariolar stalk). Tropharia are not differentiated into distinct zones and consist of syncytial lobes containing multiple trophocyte nuclei embedded in a common cytoplasm. Lobes are radially arranged around a branched, cell-free trophic core. Early previtellogenic (arrested) oocytes and prefollicular cells are located at the base of the tropharium. The vitellarium houses linearly arranged developing oocytes each of which is connected to the trophic core by a broad nutritive cord. Each oocyte is surrounded by a single layer of follicular cells that become binucleate at the beginning of vitellogenesis.

The Hemiptera of Two Sown Calcareous Grasslands. I. Colonization and Early Succession

(1) Hemiptera were sampled from two contrasting grasslands sown in April 1973 on a chalk soil which had previously grown cereals. Four replicates of the treatments were arranged in a randomized block design. Pitfall traps were used for 4 months after sowing, and vacuum net sampling late in 1973 and throughout 1974 and 1975. (2) The first colonists included typical opportunistic leafhoppers, seventeen species being recorded in 1973. The Heteroptera were varied and included many species not characteristic of calcareous grassland. (3) The most abundant Heteroptera during the whole sampling period were Nabis ferus, Notostira elongate, Trigonotylus ruficornis and Lygus rugulipennis. The last species declined in abundance from 1973 to 1975 and is not a typical grassland species. (4) The most numerous Auchenorhyncha were Arthaldeuspascuellus, which accounted for nearly half the individuals recorded, Javesella pellucida, Psammotettix cephalotes, Cicadula persimilis and Zyginidia scutellaris. A. pascuellus, Javesella pellucida and three other species declined in abundance from 1974 to 1975. (5) Although fifty species of Auchenorhyncha and forty of Heteroptera were recorded, many occurred as single specimens and equitability of both faunas was low. More species of Auchenorhyncha were recorded in 1975 than in 1974 and diversity of the faunal samples was consistently higher. Similar trends were not noted in the Heteroptera. (6) The results are discussed with reference to the establishment and management of species-rich grasslands for nature conservation.

The Hemiptera of Two Sown Calcareous Grasslands. II. Differences Between Treatments

(1) Hemiptera were sampled by vacuum insect net from replicated sown swards of two contrasting types, a fine-leaved grass mixture and a coarse one. Samples were taken in late autumn and winter 1973 and throughout 1974 and 1975. (2) Species richness of grassland Heteroptera was low and few differences between treatments were observed. Significantly more plant bugs overwintered in the coarse grassland than in the fine, with consistent, significant differences between treatments for Notostira elongate and Nabisferus. (3) Auchenorhyncha were more abundant on the coarse grassland in 1974, but on the fine grassland in 1975. Species richness, equitability, and especially diversity, were higher on the coarse sward. The fauna of the coarse grassland tended to be more diverse at any one time, but cumulatively the fauna of the fine sward was slightly more diverse. (4) Species predominant on the coarse grassland were Neophilaenus lineatus, Conosanus obsoletus, Mocydia crocea, Cicadula persimilis, Stenocranus minutes, Zyginidia scutellaris and Javesella pellucida (in the second generation only). The last four species were abundant. (5) Species predominant on the fine grassland were Deltocephalus pulicaris, Turrutus socialis, Euscelis incisus, Paluda adumbrate, Mocydiopsis attenuate, Dikraneura variata and Criomorphus albomarginatus. None of these species was abundant, and significant differences between treatments were observed only in 1975 for three of them. (6) A few species showed a response to the two grassland types which varied in time. Arthaldeus pascuellus was significantly more numerous on the coarse sward in summer 1974, but much more abundant on the fine sward in summer 1975. (7) The results are discussed in relation to the known feeding requirements of the species and to the establishment of grassland swards for nature conservation. It is concluded that mixtures of many grass species should be used to establish patches of grassland of variable structure and composition.

Variability in Calling Signals of the Planthopper Javesella Pellucida (F.) (Homoptera: Delphacidae) in Relation to Temperature, and Consequences for Species Recognition During Distant Communication

Substrate transmitted calling-signals of the planthopper Javesella pellucida were recorded at different ambient temperatures. Analysis of temporal patterns showed that most time-related parameters, such as durations and rates, were clearly temperature dependent, whereas the basic structure of the signals remained unaffected. Spectral composition and vibration patterns of single sound elements were found to be extremely variable. The results are discussed with respect to some factors that may contribute to the variation in acoustic signals recorded from planthoppers: behavioural motivation, signal modification during substrate transmission, environmental conditions. An experimental procedure was developed to test the hypothesis, that an effective system of mate recognition in planthoppers would require that distant communication is at least to some extent insusceptible to spatially varying temperature. Females were found to respond remarkably well to play-back of male calling-signals, at temperatures differing by 5°C from the male calling temperature. Temperature differences of 10°C reduced female responsivity by more than fifty per cent. It is concluded that the relevance of temperature dependent parameters to mate recognition in planthoppers is rather limited. Therefore, such parameters, which are often used in describing acoustic differentiation between populations, may not form a proper basis for conclusions on possible acoustic isolation between the populations concerned.

Vector relationships and other characteristics of barley yellow striate mosaic virus (BYSMV)

SUMMARYBarley yellow striate mosaic virus (BYSMV) was inoculated by its planthopper vector Laodelphax striatellus (Homoptera, Delphacidae) to 44 species of Gramineae, 26 of which in eight tribes were infected. The virus was not transmitted through wheat seed nor did it infect five dicotyledonous hosts of other rhabdoviruses. The most susceptible species were in the tribes Festuceae and Hordeae. Barley, Bromus spp., oats, Phalaris canariensis, Setaria italica, Sorghum spp., and sweet corn cv. Golden were diagnostic hosts. Electron microscopy of crude sap was also a sensitive diagnostic method. Properties of BYSMV were determined by injecting L. striatellus with crude sap from infected barley. Sap was infectious after 10 min at 50–55 °C but not after 10 min at 60 °C, when diluted with buffer to 10‐‐2 but not to 10‐‐3, when stored for 2 but not 4 days at 5 °C or when kept for 1 but not 2 days at 22 °C.The planthopper Javesella pellucida was an experimental vector of BYSMV but the virus was not transmitted by the leafhoppers Macrosteles sexnotatus or Psammotettix striatus (Homoptera, Cicadellidae). The latent period of BYSMV in L. striatellus was most commonly 15 or 16 days (minimum, 9 days; maximum, 29 days). The minimum acquisition access period for transmission was between 1 h and 5 h, and the minimum inoculation feeding time was 15 min. After 24 h and 8 day acquisition feeds, 30.4% and 42.8% respectively of L. striatellus transmitted BYSMV. When transferred daily, infective hoppers transmitted virus intermittently. The maximum retention of infectivity by L. striatellus was 36 days.Two of five infective females transmitted BYSMV transovarially. Larvae became infective in the second wk after hatching and transmitted for up to 3 wk.

Purification, Serology and Nucleic Acid of Oat Sterile Dwarf Virus Subviral Particles

SUMMARY Oat sterile dwarf virus (OSDV) subviral particles (SVPs) were purified from roots and stem bases of Lolium multiflorum. Electron microscopy of the preparations showed B-spiked SVPs typical of Fijiviruses (Fiji disease and maize rough dwarf-like viruses). Two sera with titres in gel-diffusion tests of 1/512 and 1/2048 were prepared against the SVPs. The sera did not react with the SVPs of maize rough dwarf and pangola stunt viruses when tested by gel-diffusion and immuno-electron microscopy. The first serum did not react with virus dsRNA or poly (1).poly(C) and the second serum had a titre of 1/8 with each of these. Poly-acrylamide gel electrophoresis of the nucleic acid from purified OSDV SVPs revealed ten dsRNA segments though only nine of these were resolved as separate bands in dsRNA extracted directly from infected plants. The genome pattern was broadly similar to but distinct from those of the known Fijiviruses. The RNA of the serologically related Arrhenatherum blue dwarf virus (ABDV), extracted directly from plants, appeared identical to that extracted directly from OSDV-infected plants. Both OSDV and ABDV were transmitted by the planthopper vector Javesella pellucida despite, in the case of OSDV, having been maintained in vegetatively propagated plants for 5 years.

Effect of European wheat striate mosaic, acquired by feeding on diseased plants, on the biology of its planthopper vector Javesella pellucida

SUMMARYTen lines of Javesella pellucida transmitted European wheat striate mosaic (EWSM) from diseased plants with an average efficiency of 31% compared to 10% efficiency for eleven lines of J. dubia. The effect on J. pellucida of EWSM, acquired through feeding on diseased plants by first and second instar nymphs, was studied in two outbred lines of hoppers. Three categories were compared: hoppers that fed on diseased plants for 7 days and became infective, hoppers that fed similarly but did not become infective, and control hoppers never fed on diseased plants and which were non‐infective. No statistically significant variation was found between these three categories in survival of nymphs to adulthood, adult longevity of either sex, total, and rate of, egg production per female, or survival of eggs to eclosion. Transovarial transmission of EWSM occurred in 6 to 43% of the progenies of infective females of J. pellucida.

Effect of European wheat striate mosaic, acquired transovarially, on the biology of its planthopper vector Javesella pellucida

SUMMARYThe proportion of infective nymphs of Javesella pellucida in the progenies of female vectors of European wheat striate mosaic (EWSM) disease ranged from 85 to 96%; 71% of these nymphs infected plants within one week of hatching. Inbreeding for one or two generations significantly decreased the viability of J. pellucida eggs, but EWSM had no effect on the viability of eggs laid by inbred or outbred vector lines. However, EWSM acquired transovarially usually increased the mortality of J. pellucida nymphs by 13 to 17%, although mortality was as high as 30% in some vector lines. EWSM, acquired transovarially for two generations, decreased the longevity of adult males and females of J. pellucida by 14%. Inbreeding for two generations resulted in 40% increase in the mortality of nymphs and more than 50% reduction in the longevity of adults.

The characters of the two wing‐forms of Javesella pellucida (F.) (Homoptera: Delphacidae), with special reference to reproduction

The characters of the two wing‐forms of <i>Javesella pellucida</i> (F.) (Homoptera: Delphacidae), with special reference to reproduction

Factors related to the two wing forms in Javesella pellucida (Fab.) (Homoptera: Delphacidae)

AbstractAt 19–22° C (18 h photoperiod/day), the effects of crowding, sex, inbreeding and of European wheat striate mosaic virus (EWSMV), inherited from infective mothers, on the induction of the two wing forms in Javesella pellucida (Fab.) were investigated. A positive linear relationship was found between the rearing density of nymphs during the first week after hatching, and the proportion of macropterous adults emerging. Both sexes responded to crowding in the same way but the proportion of macropters was normally higher in males than in females, particularly at higher rearing densities. Macropters were also more numerous in inbred than in outbred hoppers, but no effect of inherited EWSMV on the induction of wing forms was found.Macropterous and brachypterous hoppers did not differ significantly in the duration of the nymphal or adult stages; in both stages however, the females lived significantly longer than males. Inbreeding for two generations resulted in longer nymphal duration, but shorter adult longevity in both sexes.Zusammenfassungüber Faktoren, die zu den zwei Flügelformen bei Javesella pellucida (F.) (Homopt., Delphacidae) in Beziehung stehenDie Induktion der zwei bei J. pellucida auftretenden Flügelformen wurden bei 19–22° C und 18 Std. Tageslicht unter Berücksichtigung des Crowding‐Faktors, des Geschlechts, der Inzucht und des von der Zikade übertragenen Weizen‐Mosaik‐Virus (EWSMV) untersucht. Es bestand eine positive lineare Beziehung zwischen der Nymphen‐Dichte während der Aufzucht (während der ersten Wochen nach dem Schlüpfen) und dem Anteil an langflügligen Adulten. Beide Geschlechter beantworteten hohe Dichte (crowding) in gleicher Weise, doch war der Anteil der Langflügligen im allgemeinen bei den Männchen größer, insbesondere bei höherer Aufzucht‐Dichte. Audi Inzucht erhöhte das Macropteren‐Prozent. Dagegen zeigte das Vorhandensein oder Fehlen des Pflanzen‐Virus (EWSMV) im Körper der Zikade keine Beziehung zur Flügellänge. Lang‐ und kurzflüglige Zikaden unterschieden sich nicht signifikant in der Entwicklungsdauer der Nymphen bzw. Lebensdauer der Adulten. In beiden Stadien lebten jedoch Weibchen weniger lange als Männchen. Inzucht durch 2 Generationen hindurch hatte Verlängerung der Lebenszeit der adulten Tiere zur Folge.

Oat Sterile Dwarf Virus

SUMMARYOat sterile dwarf virus was found for the first time in Britain. It occurred in a crop of oats in which 15 per cent of the plants were infected. Infected plants were severely stunted, deep blue‐green in colour and produced a profusion of juvenile shoots with 2–3 much‐shortened mis‐shapen leaves. Panicle emergence was completely or almost completely suppressed. The virus was transmitted by the Delphacid, Javesella pellucida to wheat, oats, barley, meadow fescue and to Italian and perennial ryegrasses. Nearly 25 per cent of the J. pellucida population caught in the vicinity of the diseased oat crop were infective. A large proportion of non‐infective J. pellucida became infective within 2–4 weeks of feeding on infected plants.

INTEGRATED AGROECOLOGICAL CONTROL OF WHEAT APHIDS AND CICADES, STANDING FOR ENVIRONMENT-AGRICTURE-SUSTAINABLE DEVELOPMENT INTERRELATION, IN TRANSYLVANIA

The study has like objective, the modernize of integrated control management of aphids and cicades, vectors of wheat yellowishing and dwarf, by optimizing environment-agricture-sustainable development relations. The produced damages on wheat by aphids and cicades, justify the proposed research approaching. Pointed out by as on the last 30 years, the aphids dominante species Sitobion avenae, Schizaphis graminum, Metopolophium dirhodum, Rophalosiphum padi and the cicades: Psammotettix alienus, Macrosteles laevis, Javesella pellucida are registered and well knowed like vectors. Approaching a problem of economical importance and of actual scientific large interest, at national and European level, especially in conditions of profound agro-ecological changes brought by climatic warming and aridity, as the technologic and economic new conditions from agricultural area exploitations, the paper present complex researches, in systemic manner, concerning: knowledge of insects-vectors populations of viruses and micoplasma, which causes the cereals yellowishing, dwarf and nanisme; monitoring and settlement for the risk of this attack extending, with a increase potential, affecting the production of cereal grains cultures and which can causes sowing field compromise, especially of those find in monoculture or those sown early in September; the elaboration of a strategy for integrated agro-ecological control for these insects in Transylvania, through interdisciplinary research about the reductions methods of the attack in function of technological factors: selective insecticides, efficiency economic and ecologic, agro-technical methods and biotic factors: natural entomophagous; environmental protection, conservation and sustainable use of biodiversity.

The transmission of European wheat striate mosaic virus by Javesella pellucida (Fabr.) injected with extracts of plants and plant‐hoppers

SUMMARYVirus‐free individuals of the plant‐hopper Javesella pellucida (Fabr.) infected plants with European wheat striate mosaic virus (EWSMV) after being injected at 5° C. with extracts of either plants or hoppers, but extracts of hoppers provided a better inoculum. Hoppers were unable to infect plants until at least 8 days at 20–25° C. after they were injected, and nymphs fed on infected plants similarly required 8 days before they gave infective extracts. Few hoppers survived more than a week after injection with untreated extracts of hoppers or with material sedimented from them by centrifuging the extracts at 8000g, but 60–70% survived injection with purer virus preparations. Injection of the virus seemed harmless, because as many hoppers survived CO2 anaesthesis + injection, whether or not they later infected plants, as survived anaesthesis without injection. Attempts to determine the properties of the virus in vitro gave inconsistent results, but virus from hoppers was still infective after 10 min. at 30° C, 36 hr. at 5° C, precipitation at pH 4.0, storage for several months at ‐15° C, or at a dilution equivalent to 0.0014 g. hopper/ml. The best extraction medium contained 0.2 M‐Na2HPO4+ ascorbic acid + 0.01 M‐DIECA at pH 7.0–7.3. In sucrose density‐gradients, EWSMV sedimented more slowly than tobacco mosaic virus. No specific particle with which infectivity could be correlated was seen by electron microscopy.