bluuebunny/crossref_metadata_2025 huggingface dataset:
Artichoke latent virus: characterisation, ultrastructure and geographical distribution
Authors: RANA G. L. , RUSSO M. , GALLITELLI D. , MARTELLI G. P.
Published: February 2008

An isolate of artichoke latent virus (ALV‐I) obtained from a symptomless artichoke plant in Southern Italy was characterised and compared with ALV isolates from other countries. ALV occurs in California and throughout the western part of the Mediterranean basin but of Mediterranean countries east of Italy, it was found only in Israel and Turkey.

ALV‐I was readily transmissible by inoculation of sap to a moderate range of hosts, was transmitted in a non‐persistent manner by Aphis fabae, Brachicaudus cardui and Myzus persicae, but was not seed transmitted. The virus has flexuous rod‐shaped particles measuring c. 12 nm × 746 nm with a sedimentation coefficient of 145 S and a buoyant density of 1·31 g/cm3. The particles contain single stranded RNA with a mol. wt of 3 × 106 and protein composed of a single polypeptide species with a mol. wt of 33 000. Cylindrical cytoplasmic inclusions consisting of pinwheels and laminated aggregates were present in cells of naturally and artificially infected plants. ALV isolates from different geographical origin were indistinguishable from ALV‐I biologically, morphologically, serologically and ultrastructurally. These properties place ALV in the Potyvirus group, but it was serologically unrelated to 12 other potyviruses 10 of which occur commonly in Italy.
Investigations into the movement of glyphosate from treated to adjacent untreated plants
Authors: COUPLAND D. , LUTMAN P. J. W.
Published: February 2008

Transfer of glyphosate from treated to adjacent untreated plants was investigated under glasshouse conditions using wheat and Agropyron repens. When glyphosate was used at concentrations characteristic of conventional field application rates, and where shoot contact was prevented, no symptoms were observed on untreated plants. When there was shoot contact, and when glyphosate was used at 2 kg a. i./ha (10 g a. i./litre), phytotoxic effects were observed on untreated plants. At higher concentrations of glyphosate (90 or 180 g a. i./litre), typical of selective applications with ropewick or roller applicators, evidence of root transfer of herbicide was found. In pot experiments these phytotoxic effects were variable, due, perhaps, to variable amounts of root contact. Confining the roots, by growing the plants in tubes, increased the level of phytotoxicity.
Photosynthesis, respiration and evaporation of a field‐grown potato crop
Authors: LEACH J. E. , PARKINSON K. J. , WOODHEAD T.
Published: February 2008

Measurements are reported of the effects of irradiance, air temperature and water stress on the photosynthesis, respiration and transpiration of a field‐grown potato crop. The measurements, relating to one season (1974) only, were made using a field enclosure system on plots of irrigated (I) and non‐irrigated (NI) potatoes.

In the moist summer of 1974, soil moisture deficits differed little between I and NI plots, and water stress had no significant effect on the NI plants. Results show that maximum rates of net CO2 uptake (whole plants) were about 6 g h‐1 m‐2 ground area, and rates of respiration, for above‐ground and for below‐ground plant parts, were essentially constant, at about 0·3 g h‐1 m‐2 ground area, throughout the 3 months of measurement. The dependence on irradiance of the whole plants gross photosynthesis was for each measurement day adequately represented by a rectangular hyperbola relation. The season's accumulations of dry matter as calculated from these hyperbolae and from the season's measured irradiance agreed well with values derived from plant weighings.
Comparative effects of acetylene and ethylene gas on initiation of banana ripening
Authors: THOMPSON A. K. , SEYMOUR G. B.
Published: February 2008

Bananas were exposed to acetylene or ethylene at 0·01, 0·1 and 1 ml/litre, under high humidity, for 24 h at 18 °C. They were then transferred to an atmosphere of air alone for a further 4 days and during this period the respiration rate of three fruit from each treatment was measured. Ripeness was then assessed by colour score and soluble solids content.

All levels of ethylene initiated ripening. Treatment with ethylene induced a climacteric rise in respiration, an increase in the soluble solids content of the pulp and degreening of the peel. All levels of acetylene, except 0·01 ml/litre, induced a climacteric rise in respiration. Fruit treated with acetylene at 1 ml/litre had a similar colour score and soluble solids content to those ripened by exposure to ethylene. Fruits treated with acetylene at 0·1 ml/litre had a lower soluble solids content and their peel remained green. Treatment with acetylene at 0·01 ml/litre failed to initiate ripening. Sensory evaluation of fruit ripened by acetylene at 1 ml/litre indicated that the acetylene treated fruit ripened slightly more slowly. When compared at the same stage of ripeness fruits from the two treatments were equally palatable.
Pheromone‐trap catch in relation to the phenology of codling moth (Cydia pomonella)
Authors: GLEN D. M. , BRAIN PHILIP
Published: February 2008

Relationships between a pheromone‐trap catch, adult emergence and penetration of fruit by first‐instar larvae of Cydia pomonella were investigated from 1975 to 1977 in an orchard in South West England. For the first generation the times of moth emergence and catch in the pheromone trap were not significantly different; nor were male and female emergence times. The catch of moths of the first generation in the pheromone trap anticipated the appearance of their larvae in the fruit by 140–169 day‐degrees > 10 °C. Eggs hatched after 94 day‐degrees in the laboratory but in the orchard, wind and sunshine modified the microclimate so that the number of day‐degrees required for egg development, as measured by standard meteorological instruments, was affected by wind and sunshine but development lasted on average about 90 day‐degrees. This indicated a lag of 50–80 day‐degrees between the curves for trap catch and oviposition: the pre‐oviposition period in the orchard was shorter than expected from laboratory studies. In 1975 and 1976, some larvae developed to produce a second generation of moths which gave rise to a second generation of eggs and larvae, after an interval of 161 day‐degrees in 1975, but only 41 day‐degrees in 1976, indicating that in 1976 some eggs were laid before moths of the second generation were trapped. These results indicate that the first insecticidal spray against first‐generation larvae should be applied about 140 day‐degrees after the start of the reference week in which five moths of the spring brood are caught per trap. A second spray, if required to maintain insecticidal cover, should be applied about 100 day‐degrees later. A spray should be applied against second‐generation larvae immediately after the reference week for second‐generation moths.
Asymptotes of diseases caused by non‐specialised fungal pathogens in intraspecific mixed stands of cereal cultivars
Authors: JEGER M. J. , GRIFFITHS ELLIS , JONES D. GARETH
Published: February 2008

A model describing disease progress of non‐specialised fungal pathogens in intraspecific mixed stands of cereal cultivars (Jeger, Griffiths & Jones, 1981b) has been extended beyond the logarithmic phase of disease development. The extended. logistic model indicates that whatever the outcome in the early stages (disease less than or more than the mean of disease in the pure stands), disease will eventually level off at a value equal to the mean of disease asymptotes in the pure stands. The time scale involved in such levelling‐off, however, means that substantial benefit may still be expected from deployment of such mixtures.

Analytical solutions for the model are obtained for the special case where the ratio of disease asymptote to initial disease is the same for each pure stand.
The use of F(ab‘)2‐based ELISA to detect serological relationships among carlaviruses
Authors: ADAMS A. N. , BARBARA D. J.
Published: February 2008

An indirect, F(ab)2‐based ELISA was used to assess the reactions of seven carlaviruses with antisera to 16 viruses within the group and with antisera to seven other filamentous viruses. There were no specific reactions with antisera to non‐carlaviruses and serological relationships between the seven carlaviruses were generally consistent with results reported by other workers using different methods. Thus, hop latent, hop mosaic, carnation latent, potato virus S and lily symptomless viruses seem antigenically similar while American hop latent and poplar mosaic viruses are distinct from these viruses and from each other. The F(ab)2‐based method is simple and rapid and it is particularly useful for probing relationships when only small quantities of antisera are available.
Increased sensitivity of detection of plant viruses obtained by using a fluorogenic substrate in enzyme‐linked immunosorbent assay
Authors: TORRANCE L. , JONES R. A. C.
Published: February 2008

The fluorogenic substrate 4‐methylumbelliferyl phosphate (MUP) of alkaline phosphatase was compared with the chromogenic substrate p‐nitrophenyl phosphate (NPP) in tests for plant viruses by enzyme‐linked immunosorbent assay (ELISA). In tests on leaf extracts of squash infected with prune dwarf virus, Chenopodium quinoa and apple infected with apple mosaic virus (ApMV), and potato infected with potato leafroll virus (PLRV), MUP increased sensitivity 2–16 times, the smallest and greatest increases being obtained with ApMV (in apple) and PLRV respectively. In similar tests on 21 dormant PLRV‐infected potato tubers, sensitivity was increased 2–4 times with 13 tubers, but the two substrates gave the same detection end‐points with eight tubers. When individual seeds of potato plants infected with the Andean potato calico strain of tobacco ringspot virus were tested, the virus was detected in virtually all seeds by MUP‐ELISA, but detection by NPP‐ELISA was inefficient unless absorbance values were measured after overnight incubation at 4 °C, instead of after 2 h at room temperature.

In tests on Myzus persicae carrying PLRV and Sitobion avenae carrying barley yellow dwarf virus (BYDV), both viruses were consistently detected in a greater proportion of individual aphids by MUP‐ELISA than NPP‐ELISA irrespective of whether incubation was for 2 h at room temperature or overnight at 4 °C. The effeciency of detection of virus in single viruliferous aphids by MUP‐ELISA was not decreased by grouping with one or four non‐viruliferous aphids but was decreased (PLRV) or greatly decreased (BYDV) by grouping with nine. MUP‐ELISA and transmission tests to Physalis floridana seedlings (2–3 day inoculation access periods) both detected PLRV in most individual M. persicae, but the results obtained with the two methods did not correlate completely. In similar tests for BYDV in individual S. avenae, virtually all aphids transmitted BYDV to oat seedlings during a 3‐day inoculation access period but it was subsequently detected by MUP‐ELISA in less than half of them. By contrast, MUP‐ELISA detected PLRV in most viruliferous M. persicae even after they had fed for 3 days on Chinese cabbage, a non‐host for this virus.
Detection of potato virus Y in the aphid Myzus persicae by enzyme‐linked immunosorbent assay (ELISA)
Authors: CARLEBACH RACHEL , RACCAH B. , LOEBENSTEIN G.
Published: February 2008

Potato virus Y was detected by enzyme linked immunosorbent assay (ELISA) in at least 50% of groups of five Myzus persicae. The mean A405 value for groups of viruliferous aphids was 2–3 times greater than that for virus‐free ones. PVY was not detected in Aphis craccivora, A. citricola or A. gossypii, three other species which transmitted the virus to peppers, and it was detected in only a small proportion of groups of Acyrthosiphon pisum. In a series of trials, success in detection of PVY by ELISA was not correlated with the ability of other aphids from the same source plant to transmit the virus to test plants. The limitation of ELISA for quantitative assay of PVY in aphids and for epidemiological work is discussed.
The influence of form of deposit on the phytotoxicity of difenzoquat applied as individual drops to Avena fatua
Authors: MERRITT C. R.
Published: February 2008

Difenzoquat was applied as individual drops (200–400 μm diameter) to Avena fatua, using concentrations in the range 25–200 g/litre, this being appropriate to very low volume, controlled drop application. Increases in the concentration of difenzoquat within this range, or the use of larger drops, reduced the inhibition of growth of A. fatua. Increasing or decreasing the surfactant concentration from that recommended for field use also decreased performance of difenzoquat. The herbicide was more active when applied to the base of leaves and to younger leaves than to leaf tips and older leaves. In most cases reduced activity of difenzoquat was related to increased localised scorch and reduced movement of 14C‐labelled herbicide from the treated region.
Pre‐harvest retting of flax: a light microscope study of the effects of glyphosate treatment on the maturation of stem tissues
Authors: FRASER T. W. , COURTNEY A. D. , HARVEY B. M. R.
Published: February 2008

A range of glyphosate treatments was applied to flax at three stages of flowering. Spraying at a rate equivalent to 1.4 kg a. e./ha at the start of flowering gave satisfactorily uniform premature desiccation and was selected for investigation of the effects of the herbicide on stem tissues, using light microscopy.

During normal maturation, increase in fibre cell wall thickness, lignification of the fibres and differentiation of the secondary xylem continued for 3–5 wk after the beginning of flowering. This differentiation was halted by the application of glyphosate. Three wk after treatment various types of tissue damage were observed. In some sections epidermal and cortical cells showed the most damage, this being consistent with herbicide uptake at the stem surface. In other sections phloem and associated parenchyma cells showed the most damage. Disintegration of phloem and cortical cells occurred in some treated stem segments and caused separation of the fibre bundles from their surrounding tissues. This resembled the release of fibre bundles which results from conventional post‐harvest retting. The potential of glyphosate application to flax as a pre‐harvest retting technique is discussed.
Phenetic similarity among Dioscorea cayenensis cultivars as estimated by cluster analysis and minimum spanning tree
Authors: AKORODA M. O.
Published: February 2008

Two numerical taxonomic methods, cluster analysis and minimum spanning tree, were applied to classify 20 Nigerian cultivars of yellow yam (Dioscorea cayenensis). Cultivars were grown for 3 yr and 49 plant characters observed. The results were summarised as a dendrogram and an undirected minimum spanning tree. The classifications from both methods were complementary and facilitated a better understanding of the phenetic similarity between cultivars. Four main clusters were revealed with different intra‐cluster variation. The clustering pattern was not remarkably affected by the two classificatory methods employed.
Distribution between parts of the main shoot and the tillers of photosynthate produced before and after anthesis in the top three leaves of main shoots of Hobbit and Maris Huntsman winter wheat
Authors: THORNE G. N.
Published: February 2008

The top three leaves of main shoots in crops of Hobbit and Maris Huntsman winter wheat were exposed to 14CO2 at 22 and 16 days before and at 10 days after anthesis in 1978. The distribution of the 14C recovered in whole plants at anthesis and at maturity was measured. There was negligible loss of 14C between these two times, but some redistribution.

The percentage in the tillers was negligible when the flag leaf (leaf 1) was exposed to 14CO2, and otherwise less than 12% except for 14C absorbed by the third leaf at 16 days before anthesis, when it averaged 26% but was very variable. When 14C was supplied before anthesis, about 20% reached the grain whichever leaf had been supplied. The ear structures contained about 10% of that absorbed by the third leaf and 35% of that absorbed by the flag or second leaf. When 14C was supplied after anthesis, the amounts reaching the grain from the different leaves were: flag 82%, second 68%, third 56%. Most of the remainder was in the stem. The exposed leaf never retained more than 6%.

The amount of 14C that moved from the stem to the grain between anthesis and maturity was about 50% greater in the semi‐dwarf variety Hobbit than in Maris Huntsman. There was no significant varietal difference in the percentage of post‐anthesis 14C reaching the grain. The ear structures of Hobbit contained about a third more 14C than those of Maris Huntsman. An additional 90 kg N ha‐1, which increased grain yield by 46%, had negligible effects on the distribution of 14C.
Sensitivity to metalaxyl of Phytophthora infestans populations in potato crops in south‐west England in 1980 and 1981
Authors: CARTER G. A. , SMITH R. M. , BRENT K. J.
Published: February 2008

A laboratory test was developed to assess the sensitivity of field populations of Phytophthora infestans to metalaxyl. Discs of potato leaf tissue were floated upon solutions of the fungicide at different concentrations and inoculated with spores. The extent of symptom development was noted after incubation under standard conditions for 5–6 days. In preliminary experiments growth of isolates of P. infestans obtained from culture collections was severely inhibited in discs treated at 2 μg/ml. By contrast the development of an isolate obtained from a crop in Eire in which blight control with metalaxyl had failed, and known to be markedly less sensitive in vitro, was unaffected in discs treated at 100 μg/ml.

During the summer of 1980, 234 samples of P. infestans were obtained from 20 sites in south‐west England, 10 of which had received sprays containing metalaxyl and 10 of which had not. All samples were sensitive to metalaxyl applied at 2 μg/ml. In 1981, 35 sites within the same area, 30 of which had received sprays containing either metalaxyl or ofurace (a related fungicide), were similarly surveyed. Most of the 79 samples of P. infestans examined proved sensitive and at all sites the amount of blight was small. However, at three sites, including one not treated with acylalanine fungicides, strains were found which were unaffected by 100 μg/ml metalaxyl in leaf disc tests. These findings are discussed in relation to the development of resistant blight in other areas and to the use of fungicide mixtures.
Properties of a tomato isolate of Pelargonium zonate spot virus
Authors: GALLITELLI D.
Published: February 2008

A manually transmissible virus isolated from tomato plants with stunting, unfruitfulness, malformation and yellow rings and line patterns of the leaves was indistinguishable from Pelargonium zonate spot virus (PZSV) in biological, physico‐chemical and serological properties. The tomato isolate (PZSV‐T) of PZSV was seed transmitted in Nicotiana glutinosa and was detected in the pollen of this host. In sap of N. glutinosa PZSV‐T lost infectivity after diluting 10‐1 to 10‐2, heating for 10 min at 35 to 40 °C or storage at 25 °C for 7 h.

Virus particles were quasi‐spherical with a diameter ranging between 25 and 35 nm with a modal value of 29 nm. Particles sedimented as three components (TV, MV and BV) with sedimentation coefficients of 80S (TV), 90S (MV) and 118S (BV); component BV is probably an aggregate of TV. Particles were unstable in CsCl and CS2SO4 but formaldehyde‐stabilised particles banded at a common density of 1–268 g/cm3 in Cs2SO4. Particles contained a single protein species with mol. wt of c. 23000 and c. 18% single stranded RNA present as two species with mol. wts of c. 1.25 × 106 (RNA‐1) and 0.95 × 106 (RNA‐2). Mixtures of RNA‐1 + RNA‐2 were infectious and this infectivity was not enhanced by the addition of coat protein. Virus particles had a Tf (mid point of extinction when heated) of 63 °C and were readily dissociated by 0.1% SDS.

PZSV‐T was serologically unrelated to alfalfa mosaic and to 32 isometric viruses including five ilarviruses. Some properties of PZSV resemble those of ilarviruses but others are sufficiently different to suggest that it may not be a member of this virus group.
Lamium mild mosaic virus: a virus distantly related to broad bean wilt
Authors: LISA V. , LUISONI E. , BOCCARDO G. , MILNE R. G. , LOVISOLO O.
Published: February 2008

Lamium mild mosaic virus (LMMV) was compared with some strains of broad bean wilt virus (BBWV). It differed somewhat in host range from BBWV; serologically, it was only distantly related to four strains of BBWV, all belonging to serotype I, but no reaction was detected with serotype II. BBWV and LMMV were not serologically related to six comoviruses. Like BBWV, LMMV sedimented in three components and the two viruses were morphologically indistinguishable, but LMMV had more slowly migrating RNAs and coat proteins. No distinctive pathological changes were seen in LMMV infected cells.

It is proposed that LMMV be considered a distinct virus from BBWV but included with it in a new group of plant viruses.
Studies of the cereal cyst‐nematode, Heterodera avenae under continuous cereals, 1975–1978. II. Fungal parasitism of nematode females and eggs
Authors: KERRY B. R. , CRUMP D. H. , MULLEN L. A.
Published: February 2008

The development and fungal parasitism of Heterodera avenae females and eggs on susceptible cereals was studied from 1975 to 1978 in a sandy loam soil. Despite the production of many females on the roots nematode numbers declined in two years (1975 and 1978), and it is female survival and fecundity and not female numbers which often limit H. avenae multiplication.

Fungal parasites may totally destroy females on roots or result in the formation of small cysts which are often empty. Fecundity is reduced and many eggs may became infected. Parasitism of females and eggs was decreased and nematode multiplication was increased in soil treated with formalin (38% formaldehyde) at 3000 litres/ha, but because it is nematicidal and fungicidal interpretation of the effects of the sterilant are difficult. Formalin has a greater effect on H. avenae multiplication in wet summers when fungal parasites, particularly Nematophthora gynophila are more active.

Parasitised females which may be destroyed in about 7 days are fragile and difficult to extract from soil. Rates of parasitism tend to be underestimated. Approximately 60% of the females which failed to form cysts containing eggs can be accounted for by N. gynophila and Verticillium chlamydosporium.

Fungal parasitism is therefore the major factor in limiting the multiplication of H. avenae.
Weather limitations on the application of dinoseb‐in‐oil for cane vigour control in raspberry
Authors: MACKERRON D. K. L. , LAWSON H. M.
Published: February 2008

Data on crop growth suggested that only 8 days are available for timely spraying of dinoseb‐in‐oil for control of cane vigour in raspberry in east‐central Scotland. Crop records were linked with meteorological data to indicate the dates between which this 8‐day period might fall. The meteorological data were then examined to assess the probability and likely duration of conditions suitable for spraying within the period when the crop is amenable to the spray treatment.

The results indicated that unfavourable weather conditions may severely restrict the opportunities available for spray application by conventional equipment, the main limitation being high wind speed. The likelihood of rain after application putting the spray treatment at risk was found to be low.

The infinitely compound Poisson distribution was found to be suitable for graduating the observed frequency distributions of suitable spraying conditions. Diagrams of frequency distributions were produced which can be used to assess the spraying capacity required to ensure timely application over the total area of a grower's plantations. It is suggested that the approach used in this investigation could be satisfactorily applied to a wider range of crops and spraying operations.
Development of streak virus‐resistant maize populations through improved challenge and selection methods
Authors: SOTO P. E. , BUDDENHAGEN I. W. , ASNANI V. L.
Published: February 2008

Tolerance to maize streak virus (MSV) was found and rapidly incorporated into high yielding maize populations for the tropics. Methods were developed for vector propagation and rapid accurate screening of many accessions for virus tolerance in large screenhouses. Tolerance was found in only two accessions and at low frequencies. Further refinements enabled field evaluation for virus tolerance to be combined with high agronomic performance. The tolerance found is simply inherited and was fixed rapidly in breeding. Non‐strain specific tolerance was sought by collecting vectors and different indigenous host grasses from a wide area. The tolerance developed was sufficiently high hardly to affect yield of infected plants. It provided epidemiological or field resistance by reducing disease incidence to insignificance under natural conditions. This tolerance and field resistance has proved effective in several countries of East, West and southern Africa. Varieties derived from this work are now being promoted in Nigeria, and they have potential application elsewhere in the lowland tropics.
Use of a sequential probability ratio test to assess sib content in Brassica oleracea
Authors: SMITH P. , WILLS A. B.
Published: February 2008

Seed lots of F1 hybrids of Brassica oleracea are unmarketable if they contain too many sibs. The modified sequential probability ratio test (SPRT) proposed by Whitehead (1981) can be used to determine whether a hybrid seed lot meets specified quality standards for sib content and to estimate the actual proportion of sibs. It is more economical in testing than a single‐sample procedure of equal accuracy and is particularly suited for use with electrophoretic methods of sib recognition. A computer program has been written to produce control charts, for a range of test standards, for direct plotting of results.
A study of glands on cotton responsible for the high pH and cation concentration of the leaf surface
Authors: ELLEMAN CAROLE J. , ENTWISTLE PHILIP F.
Published: February 2008

Groups of hygroscopic microcrystalline particles were found on the leaf surface of cotton, Gossypium hirsutum and were shown to be produced by glands in the epidermis. The glands were hydathode‐like, about 20 μm in diameter by 25 μm long, with swollen, rounded, apices. They secreted high concentrations of magnesium and potassium and some sulphur and calcium, as indicated by X‐ray microanalysis, onto the leaf surface. The proportions of elements present in gland secretions could be altered by changing the root environment of the plant. When the microcrystalline particles were removed and made up in distilled water the resulting solution had a pH of 10.2. It was established that the glands are responsible for the high pH and cation concentrations on the cotton leaf surface. The morphology and structure of the glands was investigated by light and electron microscopy and their possible function is discussed.
Varietal differences in uptake of 32P labelled phosphate in clover plus ryegrass swards and monocultures
Authors: GOODMAN P. J. , COLLISON M.
Published: February 2008

Lolium perenne cv. S.23, L. multiflorum cv. RvP, and Trifolium repens cvs S.184 and Olwen, were grown in mixed sward and monoculture during 1979. Whereas in mixtures grass roots absorbed more 32P than clover roots, in monoculture clover generally absorbed more 32P than grass roots. This showed that grass was a very strong competitor for uptake in mixed swards.

Clover and grass monocultures absorbed most 32P from 10 or 15 cm depth in the soil, while grass in mixtures absorbed most 32P at 22.5 cm depth.

Comparing varieties, in monocultures in June, Olwen was most active in absorbing 32P at 15 cm. In August, Olwen absorbed more at 15 cm and 22.5 cm than S.184 or the grass varieties. Differences in absorption depth between varieties were less in mixtures than in monocultures. S.23 absorbed more 32P in the late season than RvP, both in monoculture and in mixtures. Thus Olwen differed from S. 184 in depth and timing of uptake, whilst S.23 differed from RvP in time of uptake. Such varietal differences could be exploited by manipulation of depth and timing of fertiliser application to increase the precision of sward management.
The effect of barley yellow dwarf virus on honeydew production by the cereal aphids, Sitobion avenae and Metopolophium dirhodum
Authors: AJAYI OLUPOMI , DEWAR A. M.
Published: February 2008

Individual S. avenae and M. dirhodum excreted significantly fewer droplets of honeydew on plants infected with BYDV than on healthy plants. S. avenae excreted less honeydew on the ears than on the leaves of wheat. M. dirhodum excreted less than S. avenae on the leaves. The size of honeydew droplets increased with the age of aphids but was not affected by BYDV infection. Possible reasons for the observed effects of BYDV on honeydew excretion are discussed.
A method of using the proportions of undamaged carrots or parsnips to estimate the relative population densities of carrot fly (Psila rosae) larvae, and its practical applications
Authors: WHEATLEY G. A. , FREEMAN G. H.
Published: February 2008

The plant‐to‐plant distribution of carrot fly damage was studied on carrots and parsnips in field and microplot experiments. The observed data were well‐fitted by the relationship In (–In q) = In L+ constant, where q is the proportion of undamaged roots and L is the number of larval mines in a sample and is proportional to the number of associated larvae, N. Hence, if N1 and N2 are the numbers of larvae at two levels of infestation on one occasion, the relative numbers present, N2:N1 are estimated by In q2: In q1 In this way the relative efficiencies of insecticide treatments can be determined within an experiment from only q1 and q2 and compared between occasions. A nomogram relating q1, q2 and treatment efficiency is provided. The method can also probably be used to compare the relative susceptibilities of host‐plant cultivars to carrot fly attack.

Guidance is given on the sample sizes needed to estimate q within 95% confidence limits and constraints on the application of the method are stated. An appropriate statistical procedure for analysing data sets on carrot fly infestations is by analysis of deviance and an example is given in an Appendix. The principles described can probably be adapted to other crop/pest problems.
Germination and growth of single‐pustule isolates of Erysiphe graminis tolerant and sensitive to tridemorph and ethirimol
Authors: LAWS F. A. , WALMSLEY‐WOODWARD DIANNE J. , WHITTINGTON W. J.
Published: February 2008

The germination and colony growth of single‐pustule Erysiphe graminis isolates tolerant and sensitive to tridemorph and ethirimol was studied on glass slides and on leaf segments sprayed with tridemorph or left untreated.

In the absence of the fungicide, neither tridemorph‐ nor ethirimol‐tolerant isolates differed from the sensitive in germination or colony growth. Germination percentages of all isolates were depressed by high temperature and low humidity, although some isolates grew well in less than optimum conditions. Differences between ethirimol‐ and tridemorph‐tolerant and sensitive isolates for colony size on untreated plants of various cultivars reflected differences in virulence to the host rather than fungicide tolerance.

The presence of tridemorph retarded the growth rate of colonies of tolerant and sensitive isolates, but the germination of tridemorph‐tolerant isolates was greatly stimulated by low concentrations of tridemorph (50 mg/litre) and was less depressed than that of the sensitive isolates by high concentrations (200 mg/litre).
Chemical suppression of the sexual stage of Leptosphaeria maculans on oil‐seed rape and turnip seed crop straw
Authors: HUMPHERSON‐JONES F. M. , BURCHILL R. T.
Published: February 2008

A selection of fungicides, herbicides and surfactants and urea were tested for their effect on the production of pseudothecia and ascospore release of Leptosphaeria maculans present on oil‐seed rape straw and turnip seed crop straw. The fungicides ethyl mercury phosphate, triarimol, fenarimol, carbendazim, tridemorph and benomyl, each at 1 g/litre, the herbicides dinoseb and diquat, each at 10 g/litre the surfactants Bradasol, Cetrimide, Deciquam 222, Hyamine 1622 and Maxonol N, each at 50 g product/litre, and urea at 150 g/litre, applied to straw before pseudothecia had formed were more than 90% effective in preventing further development. These chemicals were also effective in preventing further ascospore production when applied to straw bearing mature pseudothecia but only dinoseb and urea prevented the release of mature ascospores. The results suggest that it may be possible to break the life cycle of L. maculans by chemical treatment and thereby obviate the need for subsequent control measures.
Fungicide programmes for the control of spur blight, powdery mildew and grey mould on raspberry
Authors: SWAIT A. A. J.
Published: February 2008

Five sprays of dichlofluanid (0–1% a. i.) reduced spur blight (Didymella applanata) on canes and powdery mildew (Sphaerotheca macularis) on fruit more than five sprays of captan (0–1% a. i.). Omission of the first three applications resulted in little increase in disease but when the fourth (full bloom) application also was omitted the incidence of disease was comparable with that on untreated plants. The final (fruitlet stage) application did not further reduce disease incidence. Five sprays of dichlofluanid reduced grey mould (Botrytis cinerea) on stored fruit more than five sprays of captan. There was an increase in grey mould with progressive reductions in the number of sprays. Incidence on canes was slight and was unaffected by treatments.

A programme of five dichlofluanid sprays applied at 14‐day intervals until c. 2 wk before harvest and supplemented by a single early full bloom spray of either dinocap (0–025% a. i.), binapacryl (0–05% a. i.), triforine (0–025% a. i.), benomyl (0–025% a. i.) or replaced by benomyl (0–025% a. i.) all halved both the number of fruits infected by powdery mildew and the number of spur blight lesions on canes, compared with unsprayed controls.

Six applications of any of the following fungicides at 7‐day intervals from 23 May until 29 June 1977 reduced powdery mildew incidence on fruit, the last fungicide being particularly effective: dinocap (0–0125%), dichlofluanid (0–075%), binapacryl (0–025%), triforine (0–0125%), bupirimate (0–0075%), ditalimfos (0–01875%) and fenarimol (0–0036%). Only triforine and bupirimate reduced the incidence of mildew on shoots. Dichlofluanid, binapacryl, triforine and fenarimol all reduced the amount of spur blight on canes. The largest fruit occurred on plants sprayed with bupirimate, ditalimfos and fenarimol, and late ripening was associated with triforine treatments.
Invasion and development of juveniles of Globodera pallida in hybrids of Solanum vernei x S. tuberosum
Authors: PHILLIPS M. S. , FORREST J. M. S. , FARRER LINDA A.
Published: February 2008

Invasion and development of Globodera pallida (Pa 2) were investigated in the susceptible cultivar Pentland Crown and in two Solanum tuberosum S. vernei clones, 8917 b (3) and 12380 abc (2) with respective susceptibilities of 10% and < 1%. The numbers of juveniles per unit length of main root of Pentland Crown and 8917 b (3) did not differ, but the numbers found in the highly resistant clone 12380 abc (2) were significantly lower at all sampling dates except the last. Development of juveniles was substantially retarded in 12380 abc (2) and there was a higher ratio of males to females in both the resistant clones.

It is suggested that reduced invasion and establishment can contribute to resistance and tolerance of potatoes to potato cyst‐nematode.
Selection of a rapidly maturing population of Globodera rostochiensis by continuous cultivation of early potatoes in Ayrshire, Scotland
Authors: HOMINICK W. M.
Published: February 2008

Development of three G. rostochiensis populations was compared after 2, 3, 4, 5 and 13 wk at 12 and 15 °C on cv. Pentland Crown. The Jameston Farm (JF) and Skelmorlie populations originated from Ayrshire, Scotland, the former where early potatoes are grown annually, the latter from a farm where potatoes are grown in a conventional manner. The Feltwell population was originally from Norfolk, England. At 12 °C, nematodes from the JF population penetrated roots and developed more quickly than nematodes from the other populations. The JF population also produced the most cysts, which were the largest and contained most embryonated eggs. At 15 °C, differences between the populations were less marked, but JF nematodes invaded roots quickest and produced cysts with most eggs. These results are consistent with the hypothesis that the annual practice of early planting and harvesting to control losses caused by G. rostochiensis in Ayrshire is selecting a nematode population adapted genetically to the procedure.
Effect of surfactants and oils on the phytotoxicity of difenzoquat to Avena fatua, barley and wheat
Authors: TAYLOR M. J. , AYRES P. , TURNER D. J.
Published: February 2008

Controlled drop (CDA) and conventional applications of difenzoquat to pot‐grown Avena fatua were compared. With the recommended surfactant (0.5% v/v Agral), very low volume CDA was less effective than conventional spray application. However, addition of extra Agral or various blends of paraffinic oil with Agral and the surfactants Burtemul A2 or Burtemul P2 improved the effects of the CDA treatments. When difenzoquat was absent the additives were inactive against A. fatua. They had little direct effect on wheat and barley and did not substantially increase the phytotoxicity of difenzoquat to these crops. Oil/surfactant mixtures were less viscous than high concentrations of Agral, and so easier to spray.

In a pot experiment, smaller (150 μm diameter) drops of difenzoquat solution were more active against A. fatua than larger (200 μm‐300 μm) drops. Reduction of the spray volume within the range 40 litres/ha to 5 litres/ha also reduced phytotoxicity. An oil/surfactant additive improved the activity of all difenzoquat CDA treatments. There was slightly more effect at the lowest spray volume but interactions between additive and application treatments were not statistically significant.

When simulated rain treatments were applied 2 h or 5 h after spraying, difenzoquat controlled drop application was much less phytotoxic than a conventional 150 litres/ha treatment. However, addition of an oil/surfactant mixture markedly improved the performance of CDA. When rain was withheld for 24 h the additive had relatively less effect.

In the field an oil/surfactant mixture improved control of A. fatua by difenzoquat with both conventional and controlled drop treatments. The additive did not increase injury to the wheat crop. The oil/surfactant mixtures markedly improved the spreading and wetting properties of sprays. This reduced localised contact injury, which, it is suggested, improved uptake and translocation of difenzoquat.
Tolerance of several wild oat herbicides by a range of winter wheat varieties
Authors: TOTTMAN D. R. , LUPTON F. G. H. , OLIVER R. H. , PRESTON S. R.
Published: February 2008

Screening tests exposed varietal differences in the tolerance of winter wheat to high doses of the wild oat herbicides difenzoquat and diclofop‐methyl. Subsequent yield trials at recommended and higher doses confirmed the sensitivity of Score and Sportsman to difenzoquat and showed Atou, Bouquet and Hobbit to be less tolerant than some other varieties. In most varieties, earlier spraying proved safer than treatment at or beyond the beginning of jointing. Varietal differences with diclofop‐methyl were smaller and inconsistent.

Crops damage from these two herbicides was more severe in another experiment the following season, in which isoproturon at double the recommended dose also caused severe damage but flamprop‐methyl was fairly well tolerated by all varieties.
Antibiotic resistance in potato cultivars to the aphid Myzus persicae
Authors: BINTCLIFFE E. JANE B. , WRATTEN S. D.
Published: February 2008

Commercially‐grown potato cultivars were assessed for antibiotic resistance to Myzus persicae in a culture room at 19°C with a 2°C range and a 16 h photoperiod. The resistant rankings obtained were consistent for the following aphid metrics: maturation time, teneral adult weight, embryo complement and the production of nymphs.

Intrinsic rates of increase (rm) correlated with the above parameters of aphid growth and reproduction but this was not always the case for nymphal survival rate. The cultivars Ulster Tarn, Record and Maris Piper were relatively resistant to M. persicae and cultivars Desirée and King Edward were the most susceptible.

When the aphid clone or the culture plants were changed there was no significant effect on the relative resistance of the potato cultivars under test.

The relationship between the number of embryos in teneral adults and the production of nymphs by aphids was examined by grouping aphids in weight batches. There was a strong relationship between these two variables.
Tests for resistance to white clover mosaic virus in red and white clover
Authors: SCOTT S. W.
Published: February 2008

A range of red and white clover cultivars was tested for immunity to white clover mosaic virus. All plants became infected although some showed no symptoms. Enzyme‐linked immunosorbent assay (ELISA) and immunosorbent electron microscopy (ISEM) revealed significant differences in virus concentration between red clover cultivars and between clones of white clover artificially infected with the virus. These differences could not, however, be related to relative yield losses.
4‐Alkoxy‐2‐methylthiopyrrolo‐[2,3‐d]‐pyrimidines. A new series of anti‐cytokinins
Authors: WILCOX E. J. , WAIN R. L.
Published: February 2008

A series of 4‐alkoxy‐2‐methylthiopyrrolo[2,3‐d] pyrimidines having alkoxy groups from methoxy to hexyloxy along with the parent 4‐hydroxy compound have been tested for cytokinin and anticytokinin activity using tobacco tissue culture. None of the compounds showed any cytokinin activity but several of the compounds were strongly active as anticytokinins, the most active was 4‐pentyloxy‐2‐methyl‐thiopyrrolo[2,3‐d] pyrimidine. Increasing or decreasing the chain length resulted in a lowering of activity; the hydroxy and methoxy compounds were totally inactive over the concentration range tested. The results are discussed in relation to steric and other considerations.
Resistance to binapacryl and tetradifon, and the genetic background, in fruit tree red spider mite, Panonychus ulmi, from English apple orchards
Authors: CRANHAM J. E.
Published: February 2008

Assays on eggs of Panonychus ulmi held on leaf discs of Myrobalan plum were used to characterise strains (1) multi‐resistant to organophosphates (OPs) and binapacryl (strain BR), (2) multi‐resistant to OPs and tetradifon (strain TR), and (3) susceptible to OPs, binapacryl and tetradifon (strain EM). By crosses of EM females and BR males, and of EM females and TR males, and by repeated backcrossing with EM males under selection pressure of the acaricides concerned, two strains were produced in which the specific genes for resistance to binapacryl and tetradifon were isolated in the genome of the EM strain. Reciprocal crosses of the resulting backcrossed strains with EM, assays on the F1 eggs and the F2 haploid eggs, confirmed the presence of single major genes for resistance to binapacryl and tetradifon, and the absence of maternal effects. The expression of gene BR was incompletely dominant in response to binapacryl, whilst gene TR was effectively dominant in response to tetradifon.

Eggs of the field‐derived strain BR showed c. 50× resistance to binapacryl, 8–19 × to dinobuton, but only c. 2× to dinocap and dinoseb. The backcrossed strain was less resistant (26 ×) to binapacryl implying that resistance in strain BR was augmented by the effects of minor genes. Resistance to tetradifon (150–200 × on eggs) involved cross‐resistance to tetrasul (23 ×) and to chlorfensulphide (27×); resistance in the field‐derived strain appeared to depend on the major gene alone.

Resistance mechanisms were highly specific in their effects, so that there was no cross‐resistance to unrelated acaricides, including amitraz, dicofol, cyhexatin, formetanate, chlordimeform, and quinomethionate. Fecundity of strain BR was 44% less than that of EM; laboratory and field evidence suggest that multi‐resistant mites tend to be less fit than susceptible mites. The practical implications are discussed.
Effects of the pyrethroid deltamethrin on the acquisition and inoculation of viruses by Myzus persicae
Authors: GIBSON R. W. , RICE A. D. , SAWICKI R. M.
Published: February 2008

The pyrethroid, deltamethrin, alone or as an emulsifiable formulation, hindered infection of healthy plants with the persistent beet mild yellowing virus (BMYV) and both acquisition of, and infection with, the non‐persistent potato virus Y (PVY) and the semi‐persistent sugar beet yellows virus (BYV) by Myzus persicae in glasshouse tests.

Another pyrethroid, RU‐15525, also protected against infection with PVY. Even sub‐lethal amounts of deltamethrin decreased virus transmission by rapidly incapacitating the aphids, the effect being least with aphids most resistant to organophosphorous insecticides and to certain pyrethroids including deltamethrin. Demeton‐S‐methyl hindered infection only with BMYV. This work shows that deltamethrin restricts transmission of persistent, semi‐persistent and perhaps more importantly of non‐persistent viruses in the glasshouse, and has potential for doing the same in the field.
The effects of the repellents dodecanoic acid and polygodial on the acquisition of non‐, semi‐ and persistent plant viruses by the aphid Myzus persicae
Authors: GIBSON R. W. , RICE A. D. , PICKETT J. A. , SMITH M. C. , SAWICKI R. M.
Published: February 2008

Few Myzus persicae settled on polygodial (1 g litre‐1) or dodecanoic acid (5 g litre‐1)‐treated leaves and few nymphs were deposited. Polygodial decreased acquisition of the semi‐persistent beet yellows virus and the non‐persistent potato virus Y and dodecanoic acid that of the persistent potato leafroll and beet mild yellowing viruses, of beet yellows virus and of the bimodally‐transmitted cauliflower mosaic virus. However dodecanoic acid increased the acquisition of potato virus Y.
The use of ammonium fertilisers to reduce the severity of take‐all (Gaeumannomyces graminis var. tritici) on wheat in Western Australia
Authors: MACNISH G. C. , SPEIJERS JANE
Published: February 2008

In field experiments in Western Australia ammonium fertilisers significantly reduced the severity of root damage to wheat (Triticum aestivum) caused by Gaeumannomyces graminis var. tritici. A series of response lines depicting the effect of sources and rates of nitrogen on take‐all are presented. In general, the higher the rate of ammonium nitrogen used, the greater the reduction in the severity of take‐all. Ammonium sulphate and ammonium sulphate/mono‐ammonium phosphate mixture were more effective in reducing disease than di‐ammonium phosphate, urea or ammonium nitrate. Sodium nitrate did not reduce take‐all.