bluuebunny/crossref_metadata_2025 huggingface dataset:
Judgemental probabilities for the assessment of yield response to fungicide application againstSeptoriaon winter wheat
Authors: WEBSTER J. P. G. , COOK R. J.
Published: February 2008

Yield responses to single applications of fungicides on winter wheat varied according to several factors of which disease incidence and spray timing were the most readily identified. In order to improve spraying decisions by farmers, judgemental distributions of yield response to spray application were specified for 16 combinations of field observations, which involved crop growth stage, disease presence, weather, cultivar susceptibility, and crop site topography. An examination of 1977 results showed that 14 out of 18 recommendations would have been correct had the scheme been in use.
Purification and properties of Australian lucerne latent virus, a seed‐borne virus having affinities with nepoviruses
Authors: JONES A. T. , FORSTER R. L. S. , MOHAMED N. A.
Published: February 2008

An isolate of Australian lucerne latent virus (ALLV) from lucerne in New Zealand was mechanically transmitted to a few herbaceous hosts. It induced diagnostic symptoms in several species of the Chenopodiaceae, but was symptomless in most other hosts including lucerne and Trifolium subterraneum. It was seed transmitted in lucerne. When assayed to Chenopodium quinoa, infective C. quinoa sap lost infectivity after diluting to 10‐4, heating for 10 min at 55°C and storage for 4 days at 4°C. ALLV was purified from infected C. quinoa or pea plants by extracting sap in 0.1 m borate buffer (pH 7) containing 0.2% 2‐mercaptoethanol and clarifying with 15% bentonite suspension, high and low speed centrifugation and sucrose density gradient centrifugation. Purified virus preparations contained isometric particles about 25 nm in diameter and sedimented as three virus components with sedimentation coefficients (s20‐w0) of 56 S, 128 S and 133 S. The 56 S component appeared to consist of nucleic acid‐free protein shells. Polyacrylamide gel electrophoresis of virus preparations showed that ALLV contained a single protein species of mol. wt 55 000 and two RNA species of mol. wt 2.1 × 106 and 2.4 × 106. An antiserum to ALLV had an homologous titre of 1/256 to purified virus but failed to detect ALLV in infective sap of C. quinoa, pea or lucerne. Purified ALLV failed to react to antisera to 28 distinct isometric plant viruses including those to 10 nepoviruses.
Chemical control of beet cyst‐nematode, Heterodera schachtii, in some peaty loam soils
Authors: WHITEHEAD A. G. , TITE D. J. , FINCH P. H. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

In peaty loam soils, aldicarb or oxamyl mixed with the top 15 cm of the soil in spring before sugar beet seeds were sown, minimised invasion of the roots by larvae of the beet cyst‐nematode, Heterodera schachtii, so preventing injury to the seedlings, and greatly increased sugar yields in heavily infested soil. Small amounts of both compounds were often as effective as larger amounts. Nematode increase on sugar beet roots was slow. Aldicarb or oxamyl lessened nematode increase in four years out of five. Fumigating predetermined row positions with dichloropropene mixtures (D‐D, Telone) or incorporating aldicarb or methomyl shallowly in soil, later occupied by the roots of sugar beet seedlings, did not control the nematode, although sugar yields were sometimes increased.
Incorporation of granular nematicides in soil to control pea cyst‐nematode, Heterodera goettingiana
Authors: WHITEHEAD A. G. , BROMILOW R. H. , TITE D. J. , FINCH P. H. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Experiments at four sites in England compared control of pea cyst‐nematode, Heterodera goettingiana, on peas, Pisum sativum, obtained when 10% granules of aldicarb or oxamyl were applied to the soil in different ways. The nematode was controlled best when the granules were incorporated in the soil by rotary cultivation (L‐bladed rotavator). The granules were incorporated too shallowly by rotary harrowing (Lely Roterra); applying granules in the seed furrows during sowing, or broadcasting them at the sowing depth of 5 cm, was only effective in 1975 when heavy and prolonged rain followed sowing.
The interaction of protectants with EPTC on field bean, and tri‐allate on wheat
Authors: BLAIR A. M.
Published: February 2008

Protectants (antidotes) were tested for their potential to protect field beans (Vicia faba L.) from EPTC damage, or wheat (Triticum aestivum L.) from triallate damage. For both crops there was considerable variation in the degree of protection shown from similar treatments in different experiments. For field bean, a seed treatment of 1,8‐naphthalic anhydride (NA) at 5 mg/g seed gave some protection from EPTC applied pre‐planting at 4–8 kg a.i./ha but not in all experiments. NA also caused marked chlorosis of the foliage. N, N‐diallyl‐2, 2‐dichloroacetamide (R25788) at 20 mg/g seed severely damaged field bean in the absence of herbicide but 5 mg/g gave comparable protection from EPTC to that given by NA and did not cause chlorosis. Mixing R25788 with EPTC in the spray tank gave reduced protection. In a single experiment R4115 (chemistry undisclosed) gave some protection against EPTC damage.

For wheat, a seed treatment of 5–20 mg/g NA sometimes countered damage from tri‐allate applied pre‐planting at 1 kg a.i./ha but not generally from higher doses. R25788 sometimes protected from weight loss due to tri‐allate at 1 kg a.i./ha but not from damage symptoms, whereas R4115 at 20 mg/g seed alleviated these symptoms but did not prevent weight loss. R25788 at 4 kg a.i./ha mixed in the spray tank with the herbicide partially reduced weight loss and damage symptoms from a dose of 2 kg a.i./ha. Some treatments of R29148 gave complete protection from tri‐allate at 1 kg a.i./ha.

The results are discussed in the context of the full data from the two series of experiments.
A field enclosure apparatus for measuring crop photosynthesis
Authors: LEACH J. E.
Published: February 2008

The field enclosure is a transparent box covering a soil area of 1.5 m2. It is a semi‐closed system in which concentrations of water vapour and carbon dioxide are maintained constant: the required rate of input of carbon dioxide being a measure of the photosynthesis rate, and the rate of condensation of water, on cooling coils, a measure of transpiration. The air within the enclosure is circulated rapidly by fans to decrease concentration gradients, and under steady radiation inputs the air temperature is controlled to ±0.5 °C. Both photosynthesis and transpiration rates are corrected for air exchange with the surroundings, as measured through the injection of the inert gas, nitrous oxide.
Translocation of 14C‐labelled assimilates in cabbage during club root development
Authors: MITCHELL D. T. , RICE K. A.
Published: February 2008

The effects of infection of root systems by Plasmodiophora brassicae on the translocation of 14C‐labelled assimilates from the first and third leaves of cabbage seedlings were investigated. During the early phases of Plasmodium development, there were small differences in the distribution patterns of 14C‐labelled assimilate between healthy and infected seedlings. At the end of growth of plasmodia and during resting spore formation, both first and third leaves exported more assimilates than corresponding leaves of healthy seedlings. When the infected roots were dissected into various regions after exposure of the fed leaves to 14CO2, more assimilate accumulated in the club root region than in any other part.
Incidence, importance and virulence of Puccinia hordei on barley in New Zealand
Authors: ARNST B. J. , MARTENS J. W. , WRIGHT G. M. , BURNETT P. A. , SANDERSON F. R.
Published: February 2008

Brown rust of barley (Puccinia hordei) is widespread in New Zealand and causes crop losses in some years. The cultivars presently grown lack adequate genetic resistance but a highly resistant line has been produced. Twelve different virulence combinations were identified in the pathogen population using the Welsh differential lines; there were differences between North Island and South Island isolates; and no virulence was observed for resistance conferred by factors Pa 3 and Pa 7.
Control of Ophiobolus patch in Agrostis turf using avirulent fungi and take‐all suppressive soils in pot experiments
Authors: WONG P. T. W. , SIVIOUR T. R.
Published: February 2008

The incorporation of avirulent fungi such as Gaeumannomyces graminis var. graminis, an avirulent isolate of G. graminis var. tritici, a Phialophora sp. with lobed hyphopodia synonymous with Phialophora radiciola var. radicicola sensu Deacon and P. radicicola var. graminicola at the time of seeding Agrostis turf in pots of sterilised soil completely controlled Ophiobolus patch disease. The addition of a 5 mm layer of take‐all suppressive (TAS) soils, artifically developed by the repeated addition of live mycelium of the varieties avenae, tritici and graminis of G. graminis to soil, controlled the disease to a lesser extent. However, a 20 mm layer of a TAS soil developed from live mycelium of G. g. avenae almost completely suppressed the disease. A survey of 66 golf and bowling greens in four states of Australia showed that P. r. graminicola was the most prevalent avirulent fungus.
Variation within and between white clover varieties in their preference for strains of Rhizobium trifolii
Authors: JONES D. GARETH , HARDARSON G.
Published: February 2008

Variation within as well as between varieties of white clover (Trifolium repens L.) in their selection or preference for rhizobial strains in nodulation was studied using antibiotic‐resistant mutant strains of Rhizobium trifolii.

Significant differences between varieties were found. Cv. S100 was nodulated almost exclusively by 75 str but there was more variation within S184 and, in particular, Pajbjerg smalbladet. In this experiment 93% of the total variance was genotypic, of which 68% was due to the difference between varieties and 25% due to variance between genotypes within varieties. Significant correlations were found between the preference for rhizobial strains of plants grown from seeds and of stolon lines vegetatively propagated from the former plants, indicating that the preference for rhizobial strains is genetically controlled by the host. A considerable drift in preference towards selection of more compatible rhizobial strains by the clonally propagated stolons compared with the original white clover plants was observed.

The results are discussed from the point of view of improving symbiotic nitrogen fixation by combining highly effective and competitive Rhizobium strains with a host variety with uniform preference for those strains.
Host range, purification and serological properties of heracleum latent virus
Authors: BEM F. , MURANT A. F.
Published: February 2008

Heracleum latent virus (HLV occurs commonly in wild plants of Heracleum sphondylium (hogweed) in Scotland without causing symptoms. It was transmitted manually or by aphids (Cavariella aegopodii, C. pastinacae or C. theobaldi) to 37 of 105 species in 11 of 18 families (especially to members of the Amaranthaceae, Chenopodiaceae, Solanaceae and Umbelliferae), but was not transmitted through seed of four species tested. It has very flexuous filamentous particles c. 730 × 12 nm in phosphotungstate, with obvious cross‐banding of pitch 3–8 nm. Leaf extracts lost infectivity after 1–2 days at 22°C, 10 min at 40–50°C and after dilution 10‐4‐10‐5. Infectivity in leaf extracts was not stabilised by addition of Mg2+, Ca2+ or Ni2+, but was abolished by EDTA. HLV was purified by bentonite clarification, precipitation with polyethylene glycol (mol. wt 6000), and differential centrifugation. Its properties resemble those of the tentative closterovirus, apple chlorotic leaf spot (ACLSV), but no serological relationship was detected to this or to any of 18 other filamentous viruses, including six definitive closteroviruses. No cross‐protection was observed between HLV, ACLSV and apple stem grooving virus.
Control of potato cyst‐nematode, Globodera pallida, on tomatoes grown under glass, by applying steam or chemical nematicides to the soil
Authors: WHITEHEAD A. G. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

In a sandy loam under glass, potato cyst‐nematode, Globodera pallida, was controlled in soil to 20 cm deep, and tomato yields were greatly increased by sheet steaming for 4 h, by 977 kg methyl bromide ha‐1 or by 448 kg Telone (1,3‐dichloropropene mixture or Di‐Trapex CP (20% methyl isothiocyanate: 15% chloropicrin:65% dichloropropene‐dichloropropane mixture) ha‐1 followed by 441 kg dazomet or 11.2 kg oxamyl ha‐1. Sheet steaming, unlike the other treatments, had relatively little effect on the nematode in soil 20 to 40 cm deep. Until the apices of the plants were cut off production of fruit was curvilinear against time in all treated soil but linear against time in untreated soil.
Some effects of air temperature and humidity on crop and leaf photosynthesis, transpiration and resistance to gas transfer
Authors: LEACH J. E.
Published: February 2008

Measurements of carbon dioxide exchange and transpiration were made, at various air temperatures, on wheat and barley using a field enclosure system. From these were derived the stomatal and mesophyll resistances to carbon dioxide transfer. Optimum temperatures for net CO2 uptake were about 24°C for wheat and barley. Above these optima, as temperature increased so net CO2 uptake rates decreased, because of increasing stomatal and mesophyll resistances; transpiration rates decreased in wheat but were constant in barley.

In laboratory growth cabinets, wheat plants were subjected to different regimes of temperature and humidity. Optimum temperature for net CO2 uptake of individual leaves was 25°C. At constant humidity, a decline in net uptake rates above 25°C was associated with large increases in mesophyll resistance. At a constant 25°C, as the vapour pressure deficit (v.p.d. was increased above 1 k Pa (10 mb) v.p.d. the net uptake declined, with an increase in mesophyll resistance and a small increase in stomatal resistance. When the v.p.d. exceeded 1 k Pa at a temperature of 30°C, conditions that are experienced by field plants, then there were large increases in both mesophyll and stomatal resistances and the net uptake rates declined. Photo‐respiration, as measured by CO2 uptake in oxygen‐free air, was independent of temperature, but both dark respiration and CO2 compensation concentration increased with temperature.
Acclimatisation in the green spruce aphid, Elatobium abietinum
Authors: PARRY W. H.
Published: February 2008

Thin layer chromatography separation of 80% ethanol extracts of adult Elatobium abietinum revealed the presence of the polyhydric alcohol mannitol in aphids overwintering outdoors but not in aphids kept permanently indoors at 15°C. After 3 days at 15°C no traces of mannitol were left in overwintering aphids. Mean freezing temperatures of outdoor, unfed instar I nymphs were about 4°C lower than those of unfed instar I nymphs produced at 15°C. Mean freezing temperatures of overwintering adults were considerably higher than those of unfed instar I nymphs and showed no changes associated with time at 15°C following transference indoors. Similarly, mean freezing temperatures of Sitka spruce needles transferred to 15°C did not change. It was concluded that, although freezing was mainly avoided by supercooling, the presence of mannitol lowered the true freezing temperature of aphid haemolymph and, consequently, the actual freezing temperatures of nymphs produced under cold conditions. However, the considerable increase in freezing point temperatures caused by imbibition of plant sap masked these acclimatisation changes in feeding aphids.
A yellow mosaic disease of horse chestnut (Aesculus spp.) caused by apple mosaic virus
Authors: SWEET J. B. , BARBARA D. J.
Published: February 2008

A severe foliar yellow mosaic disease was observed in horse chestnut trees (Aesculus carnea and A. hippocastanum). Reactions in woody indicator plants grafted with diseased horse chestnut suggested the presence of an ilarvirus. Virus isolates obtained by mechanical inoculation of herbaceous test plants reacted with antisera to apple mosaic virus but not with antisera to its serotype prunus necrotic ringspot virus, or to prune dwarf virus. Yellow mosaic was induced in horse chestnut seedlings grafted with tissues from herbaceous hosts infected with horse chestnut isolates or with the European plum line pattern isolate of apple mosaic virus. Virus was detected by enzyme‐linked immunosorbent assay (ELISA) in embryo and endosperm of immature seed from infected trees but not in mature seed, or progeny seedlings.

Strawberry latent ringspot virus was detected in one of six A. hippocastanum trees with a leaf vein yellows disease.
Effects of Pratylenchus penetrans on development of strawberry wilt caused by Verticillium dahliae
Authors: MCKINLEY R. T. , TALBOYS P. W.
Published: February 2008

The nematode Pratylenchus penetrans or the closely related P. fallax occurred in three out of four strawberry plantations infested with Verticillium dahliae surveyed in Kent. When plants of cv. Cambridge Vigour were inoculated with P. penetrans and V. dahliae together in field ‘micro‐plots’ the nematode increased the rate of wilt development except when the concentration of V. dahliae microsclerotia in the soil was very low. In a pot experiment, under conditions not conducive to symptom expression, the incidence of infection was increased by nematodes in Cambridge Favourite, Cambridge Vigour and Redgauntlet; the incidence was least in Red‐gauntlet, the most resistant cultivar. The nematode appeared to cause local changes in the root cortex which aided hyphal penetration of the adjacent tissues.

Growth of strawberry plants in the absence of V. dahliae was not significantly affected even by large populations of the nematode, but growth was reduced by V. dahliae at all rates of inoculation in the field.

Infection by Verticillium did not affect the total numbers of nematode per plant at the end of the experiments, although the number per g fresh weight was greater on the small amount of white root on severely diseased plants than on the larger amount on healthy or mildly diseased plants.
Resistance of cocoa to vascular‐streak dieback disease
Authors: PRIOR C.
Published: February 2008

Water‐soluble exudates from young cocoa leaves markedly inhibited germination of spores of Oncobasidium theobromae in vitro, but there was no correlation between the inhibitory activity of a clone and its field resistance to vascular‐streak dieback. Germinating spores penetrated young leaves and the path of penetration was marked by the browning of adjacent epidermal and mesophyll cells. At the appearance of the earliest leaf symptoms the infections in the stem were confined to the vascular traces of that leaf, but spread subsequently into the secondary xylem. Clones varied in their ability to produce tyloses in response to wounding or infection and a ranking of 10 clones on tylose frequency correlated significantly with the ranking based on field resistance, but the variability was too great for this to be useful in resistance prediction. There was no significant difference in vessel size between resistant and susceptible clones. A highly significant correlation existed between vessel and branch cross‐sectional areas in six clones.
Additional phytoalexin‐like compounds in Ht‐gene resistance of corn to Helminthosporium turcicum
Authors: OBI I. U.
Published: February 2008

Four additional compounds inhibitory to germination of Helminthosporium turcicum spores were isolated from lesion‐extracts of field‐grown Ht‐gene corn (Zea mays) lines which were inoculated with H. turcicum. The compounds were named phytoalexins A3, A4‐I, A4‐II and A5. A3, A4‐1 and A4‐1 showed over 99% inhibition of H. turcicum spores at 1 mg/ml of 10% ethanol and LD50 of about 600 μg/ml. A5 showed an LD50 of about 800 μg/ml of 10% ethanol. The ultraviolet, infrared, nuclear magnetic resonance, electron impact mass spectra and field desorption mass spectra showed that these compounds might be related to the previously described phytoalexins A1 and A2. They seem to have the following functional groups: aromatic ring, hydroxyl and/or phenolic groups, carbonyl groups, probably a carboxylic acid or ester type and a long aliphatic side chain.
Factors affecting the preclimacteric period of banana fruit bunches
Authors: MARRIOTT J. , NEW S. , DIXON E. A. , MARTIN K. J.
Published: February 2008

Preclimacteric periods of banana fruits stored at 13.5d̀C were measured for bunches of several triploid cultivars including cv. Valery and a group of tetraploid clones; in the main experiment, measurements were made for about 450 bunches of 29 clones harvested mainly at weekly intervals over a period of 1 yr. A model was developed to partition the effects on preclimacteric period of the continous variables, bunch age and fruit girth at harvest and of clone difference, different agronomic treatments and harvesting dates. Preclimacteric period was well correlated with both bunch age and fruit girth, the relationship with either variable being approximately linear over the last 6 wk of bunch development. Very highly significant difference in preclimacteric period were observed between clones, difference between tetraploid clone being related in part to their diploid parentage. A small but highly significant increase in preclimacteric period was observed for bunch where the navel was removed early in bunch development compared to untreated bunch. very highly significant difference occurred between different harvesting dates but changes from the mean preclimacteric period occured mainly for bunches developing during periods when ambient temperature and bunch development rate changed rapidly and not for those developing during the warmest or coolest conditions.
The effect of cereal growth stages on the reproductive activity of Sitobion avenue and Metopolophium dirhodum
Authors: WATT A. D.
Published: February 2008

Apterous Sitobion avenae on oats were found to have a higher reproductive rate on the ears (5–95 nymphs per day) than on young leaves (3–78 nymphs per day), mature leaves (2–17 nymphs per day) or senescent leaves (2–08 nymphs per day). At each growth stage of the the host plant large aphids gave birth to more young than small aphids, but aphids of the same weight on different growth stages of the host plant had different reproductive rates. On wheat in the field S. avenae gave birth to more young on the ears but less on the leaves than Metopolophium dirhodum on the leaves.

The suitability of ears to S. avenae changed through the flowering and ripening stages. During the latter part of the milky‐ripe stage the reproductive rate of S. avenae declined and its mortality increased. The consequences of the variations in reproduction and mortality are discussed in relation to the life history and population dynamics of S. avenae and the assessment of cereal varieties for aphid resistance.
Effects of temperature on development of Otiorrhynchus sulcatus (Coleoptera: Curculionidae)
Authors: STENSETH CHRISTIAN
Published: February 2008

Development of the black vine weevil, Otiorrhynchus sulcatus, was investigated at constant temperatures from 9 to 27 oC. Pre‐adult development was completed in 200 and 130 days at 15 and 24 oC, respectively. Eggs and larvae developed at 27 oC, but no pupation took place at this temperature. The developmental threshold temperatures for eggs, larvae + pre‐pupae and pupae were 6, 2–6 and 12 oC, respectively. Reproductive maturation of females took place at temperatures from 12 to 27 oC, but only a few females became reproductive at 12 oC. Most females at 12 oC, like those at 9 oC, had a short maturation feed, but the ovaries did not develop. The pre‐oviposition period was temperature dependent. The females showed a cyclic oviposition pattern with three peaks. The significance of soil temperatures for the phenology and distribution of O. sulcatus in Norway is discussed.
The competitive ability and symbiotic effectiveness of doubly labelled antibiotic resistant mutants of Rhizobium trifolii
Authors: BROMFIELD E. S. P. , JONES D. GARETH
Published: February 2008

Doubly labelled mutants of Rhizobium trifolii, resistant to streptomycin and spectinomycin, were studied in respect of nodulating competitiveness and symbiotic effectiveness relative to the ‘wild‐type’ parent strains using Trifolium repens cv. S184 as the host plant.

A combination of antibiotic resistance, differential absorption of congo‐red and the fluorescent antibody technique permitted the rapid differentiation of all Rhizobium strains used, either from mixed inocula or from nodules. The doubly labelled antibiotic resistant mutants were inferior in terms of competitive ability for nodulation with an ineffective strain compared with the ‘wild‐type’ parent strains. A rapid method for evaluating effective antibiotic resistant strains for nodulating competitiveness is suggested. All the mutants examined were also found to be less symbiotically effective than the respective ‘wild‐type’ strains although these differences generally did not reach statistical significance. The reduced symbiotic effectiveness of the antibiotic resistant mutants was associated with an increase in magnitude of the variances for shoot dry weights, relative to that shown by the parent strains. A possible explanation for this phenomenon is presented.
Yield losses in barley, wheat and potatoes associated with field populations of'large form‘ Longidorus leptocephalus
Authors: SYKES G. B.
Published: February 2008

Three field experiments made during 1975‐77, in North and South Yorkshire, investigated the influence of ‘large form’Longidorus leptocephalus upon the yield of spring barley, winter wheat and second early potatoes.

Longidorus populations ranged from undetectable levels to 2375/litre soil. At one site estimates of nematode numbers were made twice, and gave a close agreement between the ranking order of plots. Significant negative correlations between numbers of L. leptocephalus and yield suggested that this nematode impaired the yield of these crops. For each 200 LongidoruslX of soil the estimated reductions in yield were 0–25 t/ha of barley, 0–13 t/ha of wheat and 0–55 t/ha of potatoes.
Effects of Fusarium nivale and F. culmorum on the establishment of four species of pasture grass
Authors: HOLMES S. J.I.
Published: February 2008

Cocksfoot cv. Aberystwyth S 26 and timothy cv. Scots were found to be significantly more susceptible to pre‐emergence death caused by Fusarium nivale and F. culmorum than were either perennial ryegrass cv. Gremie, or Italian ryegrass cv. RvP. The extent to which each grass was affected by Fusarium at the pre‐emergence stage was markedly influenced by both the air temperature and the level of inoculum present in the soil at the time the seeds were sown. Under all conditions, however, cocksfoot and timothy suffered greater reductions in emergence when sown in soil containing either species of Fusarium than did the ryegrasses.

Evidence is presented which suggests that the extreme susceptibility of cocksfoot and timothy to pre‐emergence damage is related to the slow germination of the former and the small seed size of the latter.

In addition to their direct effects on seedling numbers both fungi reduced the vigour of those seedlings which did emerge, cocksfoot and timothy being particularly badly affected.
Shifts in host plant resistance to the cabbage aphid (Brevicoryne brassicae) exhibited by Brussels sprout plants
Authors: DODD G. D. , van EMDRN H. F.
Published: February 2008

Seven cultivars of Brussels sprouts from different sources were tested for their relative degrees of resistance to the cabbage aphid (Brevicoryne brassicae) by estimating the Potential Increase Rate of aphid infestations. The cultivars Winter Harvest and Early Half Tall were selected as susceptible and resistant respectively and tested further. Glasshouse experiments indicated that the resistance of Winter Harvest to the aphids increased with age.

These relative levels of resistance were confirmed by population counts in the field. Aphid numbers were initially significantly higher on Winter Harvest than on Early Half Tall although significance was lost as the season progressed at a time when the characteristics responsible for the resistance mechanism ceased to be distinguishable between the two cultivars.

Analysis of the amino acid content of leaf tissues collected at monthly intervals through the aphid season enabled ‘risk rating’ predictions of aphid resistance to be made. These conformed with the shifts towards greater resistance as the plants aged noted in the glasshouse trials and endorsed the part played by amino acids in the mechanism of resistance. Total amino acid concentrations reached a peak during September and October then declined with generally lower levels of amino acids in Early Half Tall than Winter Harvest. This cultivar also possessed a greater concentration of those amino acids known to be favourable to B. brassicae although the difference between the two had diminished considerably by the end of September.

Analyses of the mustard oil glycoside levels in mature glasshouse‐grown plants did not indicate a difference between the cultivars.
The life‐history of the eriophyid mite Aculus schlechtendali on apple in South‐east England
Authors: EASTERBROOK M. A.
Published: February 2008

During 1975–77 the life‐history of Aculus schlechtendali was studied in apple orchards. The morphology of the mite and its development at a range of temperatures were studied in the laboratory.

Deutogynes of A. schlechtendali hibernated mainly in small permanently dormant buds and under loose bark on spurs and around buds on 1‐yr shoots, and moved into fruit buds between the bud burst and pink but stages and into vegetative buds as the buds began to swell. Populations on leaves reached a peak in August and mite feeding at high density caused browning of the under surfaces. The return to hibernation sites began in July.

The developmental stages of the mite are described. A generation took c. 39, 16 and 10 days at 10, 16 and 22 d̀C, respectively. Protogynes laid totals of 67–102 eggs at a rate of 1.7, 2.4 and 2.8 eggs/day at 10, 16 and 22 d̀C: deutogynes laid 21–47 eggs after hibernation at a rate of 1.3 and 1.6 eggs/day at 10 and 16 d̀C. The species was found only on cultivars and species in the genera Malus and Pyrus.
Fungi on red raspberry from lesions associated with feeding wounds of cane midge (Resseliella theobaldi)
Authors: WILLIAMSON B. , HARGREAVES A. J.
Published: February 2008

Two types of vascular lesion are described from the base of canes in plantations infested by raspberry cane midge (Resseliella theobaldi); (1) brown lobate lesions (‘patches’) confined to midge feeding areas, (2) brown lesions spreading proximally and distally from the point of infection (‘stripes’). Either or both types of lesion may be presented in individual canes. Isolations from (1) produced principally Fusarium avenaceum; isolations from tissues where (1) and (2) are contiguous gave Leptosphaeria coniothyrium and F. avenaceum; isolations from (2) arising from old cane stub wounds in the absence of midge gave L. coniothyrium.

The important secondary role of fungi in the midge blight complex is confirmed, but the involvement of L. coniothyrium in the complex is unclear because it also infects stub wounds on midge‐infested canes.
The role of pigmentation in survival of the leaf spot fungus Cercospora beticola
Authors: LYNCH F. J. , GEOGHEGAN M. J.
Published: February 2008

Both germination and survival time of spores of a pigmented strain of Cercospora beticola were directly correlated with relative humidity. Pigmented cultures, under conditions of low water availability (15%) survived 242 days' continuous exposure to light (110 lx). The ability of various strains of the fungus to survive in soil was found to be influenced by pigmentation, rate of growth, inoculum ratio in the soil and the physiological state of the organism before exposure to the soil environment.
Annual ryegrass toxicity: parasitism of Lolium rigidum by a seedgall forming nematode (Anguina sp.)*
Authors: PRICE P. C. , FISHER J. M. , KERR A.
Published: February 2008

Infection of annual ryegrass (Lolium rigidum) by Anguina sp. resulted in replacement of seeds by bottle‐shaped galls, each containing several hundred quiescent, second‐stage larvae. The biology of the nematodes, including the emergence of larvae from galls, survival in soil, and movement into and development within the host plant, has been examined. Larvae were not able to leave the galls during the dry summer, but emerged within soil 2–6 wk after normal autumn rains and following partial decay of the gall rind. Emergence took place over several months, and not all larvae emerged in any one year; they were able to survive over summer in soil both within and outside the galls.

Under suitable moisture conditions, host plants were infested by larvae which climbed up the outer surfaces, became lodged within leaf sheaths, and then gradually moved towards the centre of the plant. Larvae which reached the central or axillary meristems prior to flowering were carried up with the elongating inflorescence, and attacked developing floret primordia. The nematodes developed rapidly to the adult stage, and eggs were being laid within galls by the time the inflorescence had emerged. Second‐stage larvae hatched quickly and were the only live stage remaining after the ryegrass had died.
The effects of flower removal on the seed yield of pigeonpeas (Cajanus cajan)
Authors: SHELDRAKE A. R. , NARAYANAN A. , VENKATARATNAM N.
Published: February 2008

In field experiments carried out at Hyderabad, India with early and mediumduration cultivars of Cajanus cajan sown at the normal time, in July, removal of all flowers and young pods for up to 5 wk had little or no effect on final yield. The flowering period of the deflowered plants was extended and their senescence delayed. The plants compensated for the loss of earlier‐formed flowers by setting pods from later‐formed flowers; there was relatively little effect of the deflowering treatments on the number of seeds per pod or weight per seed. The plants were also able to compensate for the repeated removal of all flowers and young pods from alternate nodes by setting more pods at the other nodes.

The removal of flowers from pigeonpeas grown as a winter crop resulted in yield reductions roughly proportional to the length of the deflowering period, probably because maturation of these plants was delayed and occurred under increasingly unfavourable conditions as the weather became hotter.
Relationships between photosynthetic area and other growth attributes with grain yield in 6‐ and 2‐row barley genotypes
Authors: WILLIAMS R. H. , HAYES J. D.
Published: February 2008

Six‐row and 2‐row barley genotypes were grown as individually spaced plants in the field, and estimates of area of green tissue and other characters were obtained at ear emergence and maturity. Positive correlations (P<0.01) were found within both 6‐ and 2‐row types between grain dry wt per main culm and grain number, mean date of ear emergence, area of green tissue above the flag‐leaf node, and dry wt of the third leaf below the ear (F‐2 leaf). This supports the hypothesis that the magnitude of assimilate supply prior to anthesis is a very important determinant of grain yield in barley, and the possible use of the F‐2 leaf as a criterion for selection of genotypes with a large photosynthetic capacity and grain yield is discussed.
The influence of plant age on resistance of radish to cabbage root fly egg‐laying
Authors: ELLIS P. R. , HARDMAN J. A. , CRISP P. , JOHNSON A. G.
Published: February 2008

Cabbage root fly (Delia brassicae) egg‐laying around radish plants ranging in age from newly emerged seedlings to plants with flowering shoots was studied in the field and laboratory. The attractiveness of radish changed with age, one peak in egg‐laying occurring just before plants were of marketable size and further peaks as they produced flowering shoots. The pattern of egg‐laying was similar for the six radish cultivars tested, both in the field and laboratory, irrespective of whether flies did or did not have a choice of plants of different ages. At any one age, there was no correlation between egg‐laying and plant size. Selection within radish cultivars for the extremes of the range of egg‐laying preference appeared to alter the cycle of attractiveness of different radish stocks to cabbage root fly, the response being influenced by environmental conditions.
Studies on the survival and transmission of Xanthomonas manihotis on cassava seed
Authors: PERSLEY G. J.
Published: February 2008

Cassava seed which had been stored at 5 oC and 60% r.h. for 2–51 months was assayed for the presence of Xanthomonas manihotis by a leaf‐infiltration technique, using as inoculum the supernatant from seeds soaked in sterile water at 30 oC for 2–4 h. The threshold of sensitivity of the assay method was 105 cells/ml. Twenty out of 50 samples yielded the pathogen. The infested seed had been in storage for 2–18 months. Bacteria reisolated from infiltrated leaves were identical to X. manihotis in cultural characteristics, phage type and pathogenicity. Surface sterilisation or hot air treatment for 24 h at 65oC or lower did not eliminate the pathogen from infested seed. Soaking of infested seed in hot water at 60 oC for 20 min reduced the number of bacteria to less than the minimum detectable level without appreciably reducing germination. Cassava bacterial blight was observed in 8‐wk‐old seedlings which had been planted during the dry season at a site where infection from outside sources was unlikely. It is postulated that a low percentage of successful seed transmissions of X. manihotis can occur under favourable environmental conditions.
Properties of lucerne transient streak virus, and evidence of its affinity to southern bean mosaic virus
Authors: FORSTER R. L. S. , JONES A. T.
Published: February 2008

A virus obtained from naturally infected lucerne (Medicago sativa) in New Zealand reacted with antiserum to an Australian isolate of lucerne transient streak virus (LTSV). Some plants infected with New Zealand isolates showed yellow flecks along lateral veins of leaves; symptoms were transient in some lucerne plants but persistent in others. A New Zealand isolate (LTSV‐NZ) infected 14 of 39 plant species tested by mechanical inoculation, but was not transmitted by five aphid species. In sap of Nicotiana clevelandii, LTSV‐NZ was infective after storage for 4 wk at 20 oC, diluting to 10‐5, or heating for 10 min at 70 oC. Purified virus preparations contained a single electrophoretic component and a single sedimenting component (s20w= 112 S) which formed a single buoyant density component in CsCl (1.37 g cm‐3) but two density components in Cs2SO4 (1.26 and 1.32 g cm‐3). LTSV‐NZ particles were stable in 10 ITIM EDTA at pH 5, but not at pH 8, being degraded into two sedimenting components of 105 S and 92 S. Particles contained c. 18% RNA in the form of one single‐stranded RNA molecule of mol. wt 1–4 times 106, and a polypeptide of mol. wt c. 32 400. LTSV‐NZ was serologically unrelated to 24 other isometric plant viruses. However, its properties are similar to those of southern bean mosaic virus and allied viruses. The present cryptogram of LTSV is R/l: 1–4/(18):S/S:S/*.
Nematodes associated with carrots in Scotland
Authors: BOAG B.
Published: February 2008

Six hundred and fifteen soil samples were collected from 59 farms growing carrots and examined for plant parasitic nematodes. Of the potentially economically important species found the most frequently occurring were Longidorus elongatus, Rotylenchus goodeyi and Tylenchorhynchus dubius. However, numbers were generally insufficient to cause damage. At a site heavily infested with R. robustus, treatments with the oximecarbamate, aldicarb or the soil fumigant, dichloropropene significantly increased the yields of carrots by an average of 17 and 47% respectively.
A technique to assess the efficacy of non‐volatile nematicides against the potato cyst nematode Globodera rostochiensis
Authors: HAGUE N. G. M.
Published: February 2008

The assessment of larval emergence from cysts, second stage larval behaviour in soil, invasion of roots, development within roots and the final population provides a technique which can be used for evaluating the efficacy of any non‐volatile organophosphate or carbamate nematicide.

Oxamyl delayed emergence from cysts, disorientated second stage larvae in soil, delayed and reduced invasion of roots, reduced the number of eggs in the final population and markedly reduced the final population of cysts.
Control of stem nematode, Ditylenchus dipsaci, in onions, by granular nematicides applied to the soil
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , FRENCH EILEEN M.
Published: February 2008

Aldicarb at 1.4–5.6 kg a.i. ha‐l or oxamyl at 1.3–5.2 kg a.i. ha‐1 applied over the seed furrows during sowing prevented much of the damage resulting from stem nematode attack in spring‐sown onions. Rotting of bulbs in store due to stem nematode infestation was sometimes lessened by these treatments. Neither sowing onion seeds on soil ridges, nor applying aldicarb in two equal doses, one over the seed furrows during sowing, the other over the plants mid‐season, controlled the nematode better or increased onion yields more than a single equivalent dose over the seed furrows. Applied as two doses in this way, aldicarb was sometimes more effective against the nematode in summer‐sown onions than was an equivalent amount applied over the seed furrows during sowing. Only 2.5 kg or less aldicarb ha‐1 can be applied to onions without leaving unacceptable residues (>0.15 μg g‐1) in the harvested bulbs.
The use of cultivar trials records in assessing the incidence of cereal disease in England and Wales. I. Septoria nodorum in wheat and Rhynchosporium secalis in barley
Authors: ROWE JANET
Published: February 2008

The incidence of Septoria nodorum and Rhynchosporium secalis in N.I.A.B. cultivar trials of wheat and barley respectively showed marked regional and seasonal variation. Peak annual incidence of the two diseases often coincided. Levels of S. nodorum infection in winter wheat generally exceeded those in spring wheat, while levels of R. secalis in winter and spring barley were usually similar. Annual peaks in mean disease levels were associated with above average rainfall and raindays and below average temperatures, especially during the period of epidemic development. Regional variation in disease incidence reflected the association with high rainfall. S. nodorum infection in wheat was more widespread, and incidence of leaf infection was higher, than R. secalis in barley. Annual and regional incidence of S. nodorum and R. secalis in trials was similar to that recorded in the Plant Pathology Laboratory surveys of commercial crops. Disease records from cultivar trials can provide useful additional information on the behaviour of S. nodorum and R. secalis nationally.
Yam mosaic, a new potyvirus infecting Dioscorea cayenensis in the Ivory Coast
Authors: THOUVENEL J.‐C. , FAUQUET C.
Published: February 2008

The major disease affecting Dioscorea cayenensis in the Ivory Coast is caused by a virus which was transmitted by mechanical inoculation to some Dioscorea spp. and Nicotiana benthamiana. In extracts of D. cayenensis leaves infectivity was lost after 10 min at 60 d̀C but not 55 d̀C and after dilution to 10‐3 but not 10‐2. A purification procedure is described. The virus particles are flexuous filaments c. 785 nm long. The virus was transmitted by four aphid species in the non‐persistent manner, and is serologically related to four African potyviruses. The name yam mosaic virus is proposed; the present cryptogram is: */*:*/6:E/E:S/Ve/Ap, potyvirus group.
The influence of morphological differences in bracken pinnules on the foliar uptake of aminotriazole
Authors: COOK G. T. , CARR KATHERINE E. , DUNCAN H. J.
Published: February 2008

Bracken growing on an open hillside had greater development of both the upper and lower cuticular membranes than that growing under moderate shade. However, in the latter, aminotriazole uptake was less. This could be due to decreased spreading of the applied solution on the upper surface of shade‐grown fronds and a decrease in stomatal and/or leaflet hair densities on the lower surface.
Postbloom fruit drop, a new disease of citrus associated with a form of Colletotrichum gloeosporioides
Authors: FAGAN H. J.
Published: February 2008

Colletotrichum gloeosporioides was shown to be associated with postbloom fruit drop disease of citrus, a serious problem on sweet oranges in Belize.

Early symptoms are brown or water‐soaked spots on the petals, followed by corolla necrosis. Subsequently most fruitlets absciss, leaving calyces and pedicels as characteristic green ‘buttons’.

Susceptibility of flower buds to C. gloeosporioides infection was shown to increase up to the time of opening; blossom infection occurred within 18 h at 19–30°C.
The particle morphology and some other properties of chloris striate mosaic virus
Authors: FRANCKI R. I. B. , HATTA T. , GRYLLS N. E. , GRIVELL C. J.
Published: February 2008

The causal agent of Chloris striate mosaic disease appears to be a virus with polyhedral particles 18 nm in diameter usually occurring as paired structures about 18 times 30 nm in negatively stained preparations. These particles were detected in the nuclei of infected plants forming characteristic inclusions in all cells except those of the epidermis. Such particles were not detected in thin sections of viruliferous leaf hopper vectors (Nesoclutha pallida). Purified virus preparations were shown to be highly infective when assayed by feeding vector leaf hoppers through membranes and confining them on indicator plants.

In particle morphology, chloris striate mosaic virus (CSMV) differs from other viruses of Gramineae in Australia but resembles maize streak virus isolated in Africa, which however is serologically unrelated.
The resistance of two clones of perennial ryegrass and their progeny to ryegrass mosaic virus from different parts of Britain
Authors: GIBSON R. W. , HEARD A. J.
Published: February 2008

Two clones (R1 and R2) of perennial ryegrass selected from cv.S.23 pastures for immunity to a few isolates of ryegrass mosaic virus (RMV) retained immunity when inoculated manually with isolates from 10 widely‐separated sites in Britain and when grown outside at eight other sites for 1 yr. At a ninth site (Saxmundham) an isolate (RMV‐Sax) capable of infecting both resistant clones (although only with difficulty) was detected in one plot. Resistance to a Rothamsted isolate of RMV and to RMV/Sax was also shown by R1 × R2 progeny. Clone R1 yielded more than S.23 in small field plots as did R1 × R2 and R2 × R1 progeny in a pot experiment.
The toxicity of some benzimidazole fungicides to the pea aphid, Acyrthosiphon pisum
Authors: PARTIS G. A. , BAILISS K. W.
Published: February 2008

Field bean plants were treated with benomyl in a glasshouse and nymphs of Acyrthosiphon pisum were then caged on the second pinnate leaf. Soil drenches of 75 μg benomyl/ml or above increased mortality of the aphid. The concentration of methyl benzimidazole‐2–yl carbamate (MBC = carbendazim) in leaf sap, determined by a Penicillium expansum bioassay, was proportional to the concentration of benomyl applied as a soil drench or foliar spray, but lower in sprayed plants than drenched plants. The compound persisted at high concentrations in the second leaf for 4 wk but was present in low amounts in young leaves. Nymphs were also fed through membranes on artificial diets incorporating benzimidazole compounds. In this artificial system a commercial formulation of Carbendazim (Bavistin) increased aphid mortality whereas the formulation medium was inactive. Thiabendazole (as the commercial formulation Tecto 60), 2–aminobenzimidazole and benzimidazole were also inactive. It is suggested that the carbamate moiety of carbendazim causes the aphicidal activity of the compound.