bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of mixing barley cultivars on incidence of powdery mildew (Erysighe graminis) and on yield in Northern Ireland
Authors: WHITE ETHEL M. 
Published: February 2008

SUMMARYSowing mixtures of cereal cultivars has been advocated as a strategy to reduce yield loss resulting from disease in the short term and to delay adaptive changes amongst the races in the pathogen population in the long term. Six spring barley cultivars, Midas, Athos, Sundance, Mazurka, Goldmarker and Golden Promise, and seven selected paired mixtures of these, combined according to the compatibility of their resistance genes, were grown in field experiments during 3 yr. Where natural infection by powdery mildew (Erysiphe graminis) was severe, as in 1980, levels of infection in the mixtures were less than the mean of the components in monoculture. Yields were generally increased by combining cultivars; mixtures of Athos with Midas and with Mazurka gave yields over 8% higher than the mean yields of their components but these apparent synergistic effects could not be associated with reductions in levels of mildew infection.
Associations between weather factors and the spring migration of the damson‐hop aphid, Phorodon humuli
Authors: THOMAS G. G. , GOLDWIN G. K. , TATCHELL G. M. 
Published: February 2008

SUMMARYThe dates of the beginning and end of the spring migration of P. humuli, as monitored by the Rothamsted Insect Survey suction traps at Wye College and Rosemaund Experimental Husbandry Farm, were linearly regressed on temperature, rainfall and sunshine for varying periods. The beginning of migration at both sites was associated with temperature in late March and early April, and periods of rainfall in mid‐January and mid‐April, while the end of migration was associated with temperature and sunshine in mid‐ and late June, and with mid‐January rainfall. These regression equations were used to predict the timing of the migration in 1980 and 1981, those for mean maximum temperature predicting most accurately both the beginning and end of migration. The use of multiple regression equations did not increase the accuracy of predictions. The critical periods of weather are discussed in the context of the life‐cycle of the aphid.
Bioassay of metalaxyl in plant tissue
Authors: WYNN E. C. , CRUTE I. R. 
Published: February 2008

SUMMARYA method for determining the concentration of metalaxyl in methanolic extracts of plant tissue is described. Extracts were applied to filter papers in Petri dishes and covered with small volumes of lima bean agar. The growth of an isolate of Pythium ultimum sensitive to metalaxyl was related to the quantity of fungicide applied. The bioassay could detect quantities as low as 0·025 μg in the filter paper, a sensitivity which was confirmed by using 14C‐metalaxyl. Whilst untreated extracts of lettuce and brassicas were not fungitoxic to the isolate of P. ultimum employed, this was not the case with tobacco and grape‐vine. Hence alternative test organisms may be required before the method can be generally applied to all species.
Effects of environment and host on vector biology and incidence of two whitefly‐spread diseases of legumes in Nigeria
Authors: VETTEN H. J. , ALLEN D. J. 
Published: February 2008

SUMMARYSeasonal periodicity in the incidence of cowpea golden mosaic (CGM) and lima bean golden mosaic (LBGM), two whitefly‐spread virus‐like diseases, corresponded closely with fluctuations in population density of their vector, Bemisia tabaci, at two contrasting sites in southern Nigeria. Peak catches of the vector followed the onset of rains after very high temperatures during the dry season; populations declined abruptly with continuous, heavy rainfall. At Onne, B. tabaci infested legumes at emergence and remained and reproduced on them but at Ibadan infestation was delayed and there was no evidence of reproduction on legumes. B. tabaci preferred LBGM‐susceptible lima beans (Phaseolus lunatus) to resistant ones and more pupae of B. tabaci occurred on CGM‐susceptible cowpea (Vigna unguiculata) cultivars than on resistant ones but these observations did not relate to the yellow‐sensitivity of whiteflies. Resistance to CGM in cowpea, and to LBGM in lima bean, was identified amongst germplasm exposed to natural infection. Resistance was, in each case, associated with lower disease incidence, slower spread and milder expression of symptoms relative to susceptible cultivars. Vector non‐preference for resistant cultivars may have contributed to reduced secondary spread.
Pyrazophos: a fungicide with insecticidal properties including activity against chrysanthemum leaf miner (Phytomyza syngenesiae) (Agromyzidae)
Authors: LEDIEU M. S. , HELYER N. L. 
Published: February 2008

SUMMARYPyrazophos was more effective than dioxanthion against chrysanthemum leaf miner (Phytomyza syngenesiae Hardy) when applied as a mist onto bed‐grown plants irrespective of the stage of development of the pest. When pyrazophos was applied at the feeding mark stage no eggs developed but when it was applied at the young mine, mature mine or pupal stages 3–5%, 3‐1% or 45‐5% reached adulthood. Pyrazophos applied every 17‐5 days kept damage levels acceptably low.The potential of pyrazophos within an integrated control programme for chrysanthemum is discussed.
A bacterial leaf spot of Protea cynaroides (king protea)
Authors: WIMALAJEEWA D. L. S. , HAYWARD A. C. , GREENHALGH F. C. 
Published: February 2008

SUMMARYThe etiology of a new leaf spot disease on king protea was investigated. The causal organism was a Gram negative rod‐shaped bacterium with between two and seven flagella. On the basis of cultural, biochemical and physiological characters it was identified as a pathovar of Pseudomonas syringae.
Assessment of the losses caused to potatoes by the potato cyst nematodes, Globodera rostochiensis and G. pallida
Authors: BROWN E. B. , SYKES G. B. 
Published: February 2008

SUMMARYNine field trials were carried out from 1967 to 1973 on sandy loam soils in Staffordshire and Worcestershire to study the relationship between potato yield and numbers of potato cyst nematodes (Globodera spp.).Three (probably five) of these trial sites appeared to be infested with G. rostochiensis only, whereas both species occurred on the remaining four sites which grew the resistant variety, Maris Piper. Although mixtures of the two species occurred on some plots they tended to have different distributions within each trial site.The results from this work have been analysed, together with those from earlier work in the Eastern Counties on peat and silt soils, over two population density ranges, 0–40 eggs/g (5 sites) and 0–160 eggs/g (16 sites). There is no evidence of any difference in the regression of yield on eggs/g amongst the five sites in the lower range (b =–0.90 + 0.11) nor amongst 15 of the 16 sites in the higher range (b = ‐0–40 ± 0–02). Analysis of 10 sites with sufficient data in the 40–160 eggs/g range gave b = ‐0.24 ± 0.06. Thus the regression lines are essentially parallel for each of the two ranges, covering several potato varieties, soil textures and different potential yields and suggest that the varieties used are equally tolerant. The losses are 6.25 t/ha/20 eggs/g for the 0.40 eggs/g range, 1.67 t/ha/20 eggs/g for the 40–160 eggs/g range, and 2.75 t/ha/20 eggs/g as a mean for the whole range. A maximum loss of 22 t/ha is indicated.Peat soils are less dense than mineral soils but there was no need for adjustment in nematode counts. Losses caused by potato cyst nematodes are better expressed as actual yield losses rather than as percentage decreases.
Effect of soil cultivation and anaerobiosis on cavity spot of carrots
Authors: PERRY D. A. 
Published: February 2008

SUMMARYCultivating between rows and narrow beds of carrots reduced the severity of cavity spot in one year and reduced the incidence and severity in single rows in a second year on land where the disorder was endemic. Growing carrots on ridges initially reduced symptoms more than inter‐row cultivation.Soluble carbohydrates leached from carrot rootsin vitroand the quantities increased when anaerobic conditions were imposed. Untreated and cell‐free extracts of soil suspensions amended with 1% glucose and incubated anaerobically applied to carrots in the laboratory caused the outer layers of the secondary phloem to collapse resembling a cavity spot lesion. Unamended and fresh soil solutions had no effect.
Emergence of cabbage seedlots in field soils with different cropping histories
Authors: WHITE J. G. 
Published: February 2008

SUMMARYIn three non‐sterilised soils with different long‐term cropping histories of continuous mixed vegetables, continuous brassicas and continuous grassland, emergence of cabbage seedlots was lower than values obtained in laboratory germination tests. The greatest reductions occurred in soil (mixed vegetables) infested with Pythium ultimum. The presence of Pythium irregulare in the continuous brassicas soil had less effect on emergence, but the ranking for emergence of four of the seedlots was identical in the two soils. When the soils were sterilised and re‐inoculated with their respective Pythium isolate emergence was less than that in non‐sterilised soil but the rankings were similar. The pre‐emergence, and post‐emergence losses which occurred in these two soils, were controlled by seed treatment with 1 g metalaxyl/kg seed. In the continuous grassland soil although Pythium irregulare was present, emergence from most of the seedlots was high.
A method for sampling the populations of large termite nests
Authors: DARLINGTON JOHANNA P. E. C. 
Published: February 2008

SUMMARYA method for sampling the population of large Macrotermes nests is described. Fumigation with methyl bromide was followed by complete extraction of the nest contents. Termites and fungus comb fragments were separated from soil by flotation in water.Results for fumigated and live‐dug nests were compared. Sampling without prior fumigation caused the population and biomass to be underestimated by up to an order of magnitude. Caste and instar ratios were also distorted in ways that were not consistent but were affected by the size of the nest.It is therefore concluded that methyl bromide fumigation is a valuable technique for sampling the populations of Macrotermes nests.
The use of vesicular‐arbuscular mycorrhizal roots grown by the nutrient film technique as inoculum for field sites
Authors: ELMES R. P. , HEPPER CHRISTINE M. , HAYMAN D. S. , O'SHEA J. 
Published: February 2008

SUMMARYBean roots grown by the nutrient film technique and infected with vesicular‐arbuscular mycorrhizal fungi were successfully used as inoculum for red clover growing in an unsterile field site. The endophyte introduced with the roots became well established in the presence of indigenous mycorrhizal fungi.
The effect of Solanum tuberosum×S. vernei hybrids on hatching of the potato cyst nematode Globodera pallida
Authors: FORREST J. M. S. , PHILLIPS M. S. 
Published: February 2008

SUMMARYThe hatching activity of partially resistant Solanum tuberosum×S. vernei clones and susceptible cultivars was investigated in a series of tests with G. pallida conducted in pots in the glasshouse. Differences in hatching were apparent, with the partially resistant clones generally stimulating a lower total hatch than the S. tuberosum cultivars. It is concluded that reduced hatching activity can make a small contribution to overall resistance and perhaps also to the tolerance of a clone to G. pallida.
The effect of soil‐applied granular pesticides and irrigation on the yield of sugar beet in fields infested with Trichodorus viruliferus
Authors: COOKE D. A. 
Published: February 2008

SUMMARYIn field samples taken on a grid pattern during four winters over an 80 ha farm there were many Trichodorus viruliferus (up to 3000/litre soil) in light soils but few in heavier soils. Depth samples taken during the summer showed Trichodorus to be the only nematode genus which was more numerous below plough depth than in the plough layer. In field experiments in the most heavily infested part of the farm, soil‐applied granular pesticides did not increase sugar yields following the dry spring of 1982; aldicarb increased sugar yields in one experiment following the wet spring of 1983 although it, and other granular pesticides, did not affect yield in an adjacent experiment where T. viruliferus were fewer. Irrigation during the dry summer of 1983 maintained relatively large populations of T. viruliferus, whereas in unirrigated plots without aldicarb populations declined by over 50%. Economic thresholds for T. viruliferus in 1983 at Broom's Barn were about 700/litre in unirrigated soil and 300/litre in irrigated soil.
Senescence and net photosynthesis of the flag leaf and grain growth of wheat in response to fungicide
Authors: DAVIES W. P. , KETTLEWELL P. S. , GREEN HELEN J. , HOCKING T. J. , JARAI MARIANNA M. 
Published: February 2008

SUMMARYGreen leaf area and net photosynthesis of the flag leaves of Avalon and Maris Huntsman winter wheat crops were studied in relation to grain growth following the application of the fungicide propiconazole at flag leaf emergence. Disease levels were low during grain‐fill, and were not significantly affected by the fungicide. Propiconazole significantly maintained green leaf area and photosynthesis per unit area during the period of rapid flag leaf senescence, but it had no effect on stem weight, grain growth or yield.
Floral biology and pollen viability of parental lines of onion hybrids
Authors: ALI M. , DOWKER B. D. , CURRAH L. , MUMFORD P. M. 
Published: February 2008

SUMMARYParental lines (inbred and hybrid male‐sterile lines and inbred pollinators) of prospective F, hybrids from the NVRS spring‐sown bulb onion breeding programme were examined to study their floral biology and aspects of pollination under glasshouse conditions. Inbreeding depression occurred in both pollinator and male‐sterile inbreds in terms of reduced flower numbers per umbel and a greater proportion of defective pistils. Male‐sterile and male‐fertile lines differed in their stigma and style characteristics and pattern of development. At flower opening, the styles of male‐sterile lines were longer and the stigmatic knob became receptive relatively sooner. The inbred male‐sterile line II/3 ms appeared to have a reduced receptive area on its stigmatic knob and remained receptive for a relatively shorter period. Individual lines differed for time of flowering, nectar content and its sugar concentration, and in their effectiveness as male and female parents as judged from pollen tube growth down the style in specific pairings. Assessment of pollen viability using the fluorescein diacetate test did not correlate with assessments based on pollen grain germination and subsequent growth down the style, perhaps as a result of differential receptivity in the inbred lines tested.These results are discussed in relation to future hybrid seed production.
Patterns of spread of the non‐persistently transmitted bean yellow mosaic virus and the persistently transmitted subterranean clover red leaf virus in Vicia faba
Authors: JAYASENA K. W. , RANDLES J. W. 
Published: February 2008

SUMMARYPatterns of spread of two aphid borne viruses, the non‐persistently transmitted bean yellow mosaic virus (BYMV) and the persistently transmitted subterranean clover red leaf virus (SCRLV), were compared simultaneously in field plots of Vicia faba minor grown in a Mediterranean climate (winter‐spring growing season, and dry summer).Spread from a primary source was mapped following the artificial introduction of virus alone, or virus with vector, at the centre of the plots. BYMV spread rapidly from the virus source whether or not vectors were introduced with the virus. By contrast, SCRLV spread from the source only when plants were also artificially infested with the vector Aulacorthum solani. An attempt was made to evaluate the importance of secondary spread of both viruses by assessing the degree of clumping of infected plants that occurred outside the primary sites of virus introduction. BYMV‐infected plants were clumped in each treatment irrespective of whether the virus was introduced alone or with vector, as well as in control plots. Clumping of SCRLV occurred only when the vectors were introduced on virus source plants at the beginning of the experiment.Times of spread were determined both by exposing trap plants at 4‐weekly intervals throughout the 30 month trial period, and by analysing the rates of spread in experimental plots between June and November in one growing season. Both viruses spread in the spring when vectors were flying, but negligible spread of the viruses was observed in the autumn despite aphid flight activity.Times of flight of the four main aphid vector species were continuously monitored with yellow water traps. A major spring and a minor autumn flight peak were observed for Aphis craccivora, Macrosiphum euphorbiae, Aulacorthum solani and Myzus persicae. Aphid flights occurred predominantly in weeks when the mean temperature was in the range 13–17°C. Rainfall above 7 mm per week appeared to affect flights only when mean weekly temperatures were outside the range 13–17°C.
Flowering of contrasting white clover varieties in relation to daylength in controlled environments and in the field
Authors: NORRIS I. B. 
Published: February 2008

SUMMARYThe effect of 12, 14 and 16 h photoperiods, given consecutively, on flower production in 10 varieties of white clover (Trifolium repens) in controlled environments, is described. The effect of natural daylengths from September to July on the same plants in the field was also studied in the following year. Relationships between morphological and physiological traits and flowering were examined.In controlled environments most plants flowered under the longest days, three times as many in the 16 h daylength as in the 12 h. Larger leaved types had a higher proportion of reproductive plants than did smaller leaved types.Floral initiation was not observed in the field until daylengths were in excess of 15 h.Increasing daylength increased flower production, floret and ovule numbers but did not appear to increase nectar production significantly.
Establishment and yield of three ryegrasses following aldicarb use, and changes in abundance of plant parasitic nematodes
Authors: SPAULL A. M. , MEWTON P. G. , CLEMENTS R. O. 
Published: February 2008

SUMMARYPure swards of Lolium multiflorum, L. multiflorum var. westerwoldicum and L. perenne sown in August had greater yields than autumn on areas treated with either 5 or 10 kg a.i./ha aldicarb than on untreated areas. Total annual dry matter yields increased by larger amounts where the greater rate of aldicarb was applied; throughout the trial, L. perenne was usually less affected by treatment than the other two grasses.Plant‐parasitic nematodes were more numerous on untreated than treated plots and were fewest in areas receiving the larger application (except in the second harvest year). Numbers of Tylenchorhynchus and Helicotylenchus were affected most by treatments; abundance of Paratylenchus and Criconemella were little altered.Stem‐boring Diptera invaded tillers of all three grasses but infection was least in L. perenne. Invasion occurred only on untreated plots in the establishment year and some yield benefit probably resulted from their control. In subsequent years invasion was similar on treated and untreated areas. Effects on other, non‐target organisms were not assessed.Ectoparasitic nematodes multiplied more in L. multiflorum plots than in others during the first full‐harvest year. The next year numbers of Paratylenchus only were greater in plots of L. perenne than in other plots.Sward persistence of L. multiflorum var. westerwoldicum was better on treated than untreated areas.It was concluded a) that aldicarb use greatly decreased nematode numbers and yields from treated areas were larger than from those untreated; b) that sward persistence was similarly improved following aldicarb use and c) that ryegrasses differed in their suitability as hosts to ectoparasitic nematodes.
Problems in field selection for resistance to carrot fly (Psila rosae) in carrot cv. Long Chantenay
Authors: ELLIS P. R. , DOWKER B. D. , FREEMAN G. H. , HARDMAN J. A. 
Published: February 2008

SUMMARYIn field trials between 1973 and 1982 families of carrots of cv. Long Chantenay were assessed for their resistance to carrot fly (Psila rosae). In some but not all years, families selected for their observed resistance in earlier trials seemed more resistant than the parent line. In more than half the trials there was an association between carrot fly damage and root density, there being less damage on those families from which more roots were harvested. Thus, family selection within cv. Long Chantenay did not lead to a consistent improvement in resistance to carrot fly. Alternative strategies for achieving plant resistance to this pest are discussed.
Stem canker (Rhizoctonia solani) of maincrop potatoes.
Authors: HIDE G. A. , READ P. J. , SANDISON JANET P. 
Published: February 2008

SUMMARYIn two years, potato plants were sampled at 1 ‐ or 2‐weekly intervals from plots planted with seed tubers bearing sclerotia of Rhizoctonia solani (black scurf) and with seed without sclerotia either infested or not with cultures of R. solani at planting. Sprouted King Edward seed was used in 1981 and sprouted or non‐sprouted King Edward and Pentland Crown in 1982.Stem canker decreased the number of aerial stems and decreased plant height by a constant amount throughout growth. The length but not the number of lateral stems (branches) was increased. Total fresh weight of foliage was decreased although few differences were significant, but the weight of foliage on main stems was decreased and the weight of laterals increased. Total leaf area was decreased by a constant amount throughout growth and the proportion of the leaf area on lateral stems increased. Infection increased % dry matter of main stems and dry weight per unit area of leaves and decreased total dry weights of stem bases and roots.Tuber production was delayed on infected plants although more tubers were initiated later, and at harvest in 1981 infected plants had more tubers < 5 cm than healthy plants but similar numbers of larger tubers. Fresh weight of tubers increased at a similar rate on healthy and infected plants, but the infected plants yielded 50 g less than healthy throughout tuber bulking in 1981 and 20 or 80 g (King Edward, respectively sprouted and non‐sprouted seed) or 110 or 170 g (Pentland Crown) less than healthy in 1982. In both years, neither seed‐borne nor soil‐applied inoculum significantly decreased total or ware (>40 mm) tuber yields at harvest.In both years soil‐applied inoculum had greater effects on plant growth and yield than seed‐borne inoculum.