bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the bacterial diseases of Sudan crops
Authors: SABET K. A. , ISHAG FARIDA 
Published: February 2008

SUMMARY Xanthomonas phaseoli survived for more than 18 months in press‐dried dolichos bean leaves kept in the laboratory. Survival of the organism in pure culture, or in leaf trash mixed with the soil, depends on soil moisture, being longest in air‐dried and shortest in water‐saturated soil. In completely water‐saturated, or in completely air‐dry soil, no effect of soil autoclaving is observed. In moistened soil survival is longer in autoclaved than in untreated soil. In the absence of demonstrable phage activity, disappearance of the organism in water‐saturated soil is attributed to prevailing anaerobic conditions, and in moistened soil to the action of competitive saprophytes. In air‐dry soil the organism is preserved by drying.The bacteria reach the seed, via the placenta, when young pods, less than 2 cm long, become infected by artificial inoculation: they do not invade the vascular tissues. Survival of the bacteria in the seed is considered of a relatively little importance in practice.Seedling infection is characterized by elongated brown lesions on the veins of the simple and first and second trifoliate leaves; those parts of the lamina dependent on affected veins become chlorotic and flaccid. Vein lesions show the pathogen in the vascular bundles, which exhibit no tissue differentiation. A strain of X. phaseoli from Vigna radiata (weed plant) also infects dolichos bean. Its minimal infective dose on Dolichos is considerably higher than that of the dolichos bean strain.The dolichos bean disease can be transmitted by heavy infestation of the whitefly Bemisia tabaci.
The effect of fungicidal treatments on sporulating capacity in relation to the control of coffee berry disease
Authors: NUTMAN F. J. , ROBERTS F. M. 
Published: February 2008

SUMMARYThe capacity of the maturing wood of the branches of Coffea arabica to produce conidia of Colletotrichum coffeanum Noack, the causal agent of coffee berry disease, is profoundly affected by fungicidal treatments. The effect differs according to the epidemiology of the disease. When the main source of inoculum is from the wood, the reduction in the sporulating capacity persists throughout the crop‐season, and good control of the disease results. When the main source of inoculum is from diseased berries, reinfection of the branches takes place, the sporulating capacity of sprayed branches rises above that of unsprayed ones, and there is indifferent or no control. Evidence from field trials suggests that the correct timing of early season spray schedules may be related to the part of the annual rhythm of sporulating capacity at which they are applied. As this rhythm is determined by rainfall, and varies from year to year and from place to place, the correct time for the start of a schedule should be predictable from meteorological data.
Fungicidal activity and chemical constitution
Authors: CLIFFORD D. R. , DEACON A. C. , HOLGATE MARGARET E. 
Published: February 2008

SUMMARYStructure/activity relationships for members of five homologous 4‐(1‐substituted alkyl)‐2,6‐dinitrophenols and apple mildew are discussed with special reference to their hydrophobic bonding constants π. It is suggested that π values may be of use in predicting potential anti‐mildew fungicides with similar modes of action to those of the substances studied.
Seed treatments with Vitavax for the control of loose smut of wheat and barley
Authors: MAUDE R. B. , SHURING CATRIONA G. 
Published: February 2008

SUMMARYSeed dressings with Vitavax—75 % w.p.—eliminated Ustilago nuda in spring barley seeds and greatly reduced infection due to U. tritici in winter wheat. Emergence and yield of these crops were not adversely affected. Seed soak treatments including 0·2 % aqueous Vitavax for 6 h at 30 °C (wheat and barley), 0·2% thiram for 24 h at 30 °C (barley) and 0·2% Vitavax for 1 h at 30 °C (barley) also rid the seeds of infection. In other tests with barley 2 h soaks in 0·2 % aqueous suspensions of Vitavax at 30 °C gave equivalent control to 12 h soaks in 0·2% thiram at 30 °C.
An investigation of the toxicity of insecticides to birds' eggs using the egg‐injection technique
Authors: DUNACHIE J. F. , FLETCHER W. W. 
Published: February 2008

SUMMARYTwenty‐five insecticides have been tested for their toxicity to hen embryos at various concentrations, using an egg‐injection technique. Of the two major groups, the organophosphorus compounds are much more toxic than the organochlorine. Most organophosphorus compounds lower the hatch rate and cause teratogenic effects at 100 ppm. Most organochlorines do not harm the embryo at high dosages (up to 500 ppm), with notable exceptions to this among the cyclodienes. However, starvation of the hatched chicks suggests that the majority of organochlorine compounds can kill at this stage, though fed chicks survive. The solvent used affected toxicity; in general, insecticides are more toxic to the embryo when dissolved in corn oil than when dissolved in acetone. If these findings can be applied to wild birds, it can be assumed that the vast majority of insecticides are harmless to birds' eggs. They are either not toxic in the concentrations so far found in this country, or else unlikely to pass through the mother bird to the egg.
Aggressive behaviour in related and unrelated wild house mice (Mus musculus L.)
Authors: ROWE F. P. , REDFERN R. 
Published: February 2008

SUMMARYAggressive behaviour was observed to be rare in small family groups of confined wild house mice, Mus musculus L. Unrelated mice were attacked when they were introduced to a family group and in their presence intra‐family aggressive behaviour increased. When two family groups of mice were allowed to meet there were frequent aggressive encounters between unrelated animals and the two groups remained separate.Resident mice were found to be aggressive towards males and females individually isolated and returned to their own family after 2 or 3 weeks absence but not after 1 week. The possibility is discussed that in wild mice odour discrimination influences the dispersal and build‐up of free‐living populations.
The potential of Chrysopa carnea as a biological control agent of Myzus persicae on glasshouse chrysanthemums
Authors: SCOPES N. E. A. 
Published: February 2008

SUMMARYLarvae of C. carnea lived for 13‐4 days at 21·1°C and consumed an average of 385 second‐instar Myzus persicae or 425 Aphis gossypii. At 15·5°C the larval lifespan was 29·5 days though the consumption of M. persicae was hardly affected. M. persicae developing on glasshouse chrysanthemum plants were eliminated by the introduction of 1‐day‐old larvae at aphid: chrysopid ratios up to 50:1; third‐instar larvae achieved control at a ratio of 200:1. At very low aphid densities control was less effective.Control by C. carnea of aphid populations developing on glasshouse chrysanthemums can be predicted mathematically.
Build‐up of tomato brown root rot caused by Pyrenochaeta lycopersici Schneider and Gerlach
Authors: LAST F. T. , EBBEN M. H. , HOARE R. C. , Turner E. A. , Carter A. R. 
Published: February 2008

SUMMARYThe incidence in unheated glasshouses of tomato brown root rot (BRR) was recorded on five successive crops starting with the first ever grown on the experimental site. In the protected environment the changes followed a pattern that was defined mathematically, the regression linking angular or logit transforms of per cent BRR, observed at different intervals after planting, accounting for c. 72% of the variation. Rates of build‐up, seemingly related to initial amounts of inocula, increased in successive seasons, there being more BRR in the fifth season than in the first. Four per cent BRR recorded 5 weeks after planting increased threefold during the next 3 months to 12 %, but in later years, when amounts of early‐season infection were doubled to 8%, the incidence of root rot subsequently increased five times.Tomato roots colonized by Pyrenochaeta lycopersici either brown and rot or become corky. The proportion of end‐of‐season BRR attributable to corkiness increased from the first to fifth seasons.The monthly increments of fruit yield were inversely proportional to the incidence of BRR.
Growth and wilt (Verticillium dahliae) development in strawberry cultivars over a transition between two soil series
Authors: TALBOYS P. W. , BENNETT MARGERY 
Published: February 2008

SUMMARYOn a site infested with V. dahliae the incidence of wilt was low consistently in strawberry cvs Talisman and Redgauntlet, high in Merton Herald and Gorella, and very high in Merton Ruby, Cambridge Vigour, Prizewinner, Templar and Crusader.Changes in mean volume per plant for the whole population of each cultivar were closely related to disease incidence and therefore differed between high‐resistance and low‐resistance cultivars.Height and spread measurements of diseased and symptomless plants in certain cultivars showed differences in the severity of the effect of the pathogen on growth that were not closely related to wilt incidence.Gradients of disease incidence and plant growth in 1966 and 1967 were associated with a transition from one soil series to another. Review of two earlier experiments on the same site revealed a similar gradient of disease incidence in 1963‐64, but a reversed gradient in 1960‐62. Variations related to soil conditions were smaller in the earlier experiments than in 1966‐67.
Tomato leaf mould: its assessment and effects on yield
Authors: SMITH PAULINE M. , LAST F. T. , KEMPTON R. J. , GISBORNE J. H. 
Published: February 2008

SUMMARYWhen the natural incidence of Cladosporium fulvum Cooke, occurring at a relatively late stage of cropping, was controlled with fungicides, comparisons with unsprayed control plants showed that there was an interval of c. 6 weeks between the incidence of severe infection, when the fungus was colonizing at least 50 % of the host's leaf area, and fruit yield decreases.Eye estimates made on separate leaves usually over‐estimated the percentage of infection. Correction factors were derived from the regression of eye estimates on infected areas calculated from leaf tracings. Whole‐plant infection indices were obtained by averaging corrected values of percentage infection separately assessed on leaves immediately above each fruit truss.Although dichlofluanid and tank‐mixed zineb decreased the incidence of C. fulvum more than captan sprays, tomato yields (including green fruit) were increased similarly by all three fungicides from 2·99 to an average of 3·51 kg/plant during c. 3 months' picking. Decreasing the intervals between successive sprays from 21 to 7 days greatly decreased leaf mould infection but did not significantly affect yields. Restricting applications to plant tops (namely foliage from the fourth‐youngest truss to the mainstem apex) gave yield benefits equal to those gained from sprays applied to whole plants.
Effects of nitrogen and glucose on saprophytic survival of Ophiobolus graminis in buried straw
Authors: SCOTT P. R. 
Published: February 2008

SUMMARYCalcium nitrate prolonged the saprophytic survival of Ophiobolus graminis (Sacc.) Sacc. in artificially colonized straws buried in soil in the laboratory, whether supplied to the soil (at 12·5 or 100 mg nitrogen/100 g soil) or to the straws before colonization (at 0·5 or 1·0 g nitrogen/100 g straw). Glucose (at 2·5 g/100 g soil, and at 10 g/100 g straw) shortened survival.When straws colonized in the presence of 0·5 g nitrogen/100 g straw were buried in soil supplied with 14·1 mg nitrogen/100 g soil, the level of soluble soil nitrogen reached equilibrium at 2–4mg/100g soil; this allowed rapid straw decomposition and, although the added soil nitrogen prolonged survival in straws that remained undecomposed, it also accelerated substrate exhaustion. Addition of 100 mg nitrogen/100 g soil was supra‐optimal for survival: although some nitrogen was necessary for maximum survival, the equilibrium concentration of soluble nitrogen (24–56 mg/100 g soil) was high enough in this case to have an inhibitory effect in addition.
Field biology and control of Phytophthora parasitica on papaya (Carica papaya) in Hawaii
Authors: HUNTER J. E. , BUDDENHAGEN I. W. 
Published: February 2008

SUMMARYEpidemic attacks of Phytophthora parasitica on papaya fruits developed during wet, windy weather, but declined rapidly when the weather became dry. During rain, abundant sporangia were liberated from the mycelial mats on infected fruits, but none was trapped in dry air.Collar rots and tree collapse caused by root rot occur irrespective of spray treatments and previous aerial infections on the same tree: they are no more prevalent in blocks with abundant aerial infections than in blocks with none. Basal rots occurred earlier and more frequently on plantings near abandoned diseased fields: they were scattered randomly and appeared before aerial infections.It is suggested that new outbreaks might be initiated from seeds of infected fruit, in which chlamydospores have been found, or from infected nursery seedlings. Drosophila spp. were found to be occasional vectors of sporangia.Control of aerial infections was obtained with maneb, basic copper sulphate, captan or difolatan. Spraying only the upper half of the acropetally developing fruit cluster gave much better control than spraying only the lower fruits.
The possible role of pathogenic fungi in local degeneration of Salvinia auriculata Aublet on Lake Kariba
Authors: LOVELESS A. R. 
Published: February 2008

SUMMARYA patchy degeneration of weed mats of Salvinia auriculata in the sheltered mouths of rivers draining into Lake Kariba was reported in 1962 to be associated with a fungal attack. Laboratory isolations from degenerating plants yielded a saprophytic Alternaria sp. and a parasitic Spicariopsis sp. Degenerating plants failed to transmit the disease when placed among healthy plants, and the results of inoculation experiments with spores of Spicariopsis sp. were inconsistent with this fungus being a primary pathogen.The characteristic feature of degeneration in the field was a mosaic of alternating ‘islands’ of diseased and healthy plants. Although the diseased plants showed the symptoms associated with Alternaria sp. and Spicariopsis sp., their characteristic distribution provided circumstantial evidence that degeneration was physiological in origin. This view was strengthened by the fact that sudd plants growing on degenerating areas of the Salvinia‘carpet’ were usually chlorotic. The presence of symptoms caused by the parasitic Spicariopsis sp. on degenerating plants could be explained by postulating that, after the plants have begun to degenerate, they are predisposed to infection by this fungus.The association of degeneration with a particular type of riverine site suggests that a seasonal investigation of the hydrobiological conditions accompanying the development of weed mats at such sites would indicate the type of factor responsible for the disease. The original hope for a biological control of Salvinia auriculata by means of a parasitic fungus remains a theoretical possibility.
Splash dispersal of fungus spores and fungicides in the laboratory and greenhouse
Authors: HISLOP E. C. 
Published: February 2008

SUMMARYA laboratory technique is described for the production of drops of simulated rain in which fungal spores were suspended. When such drops containing conidia of Botrytis fabae impacted on a target leaf the secondary droplets produced infections on receptor broad bean leaves. The capacity of fungicides applied to the target leaf to redistribute in secondary splash droplets was examined in terms of the infectivity of the spores in the droplets. The extent to which a copper fungicide reduced infection on the receptor leaves was related to the level and tenacity of the fungicide deposit on the target leaf. The effect of wetting agents on the redistribution of this fungicide could probably be explained by their influence on the tenacity of the initial deposit. In general the capacity of different fungicides to inhibit infection by the secondary droplets was related to the inherent toxicity of the fungicides to B. fabae. Implications of the dispersal of spores and fungicides by rain splash are briefly considered with reference to field conditions.
A laboratory method for assessing the toxicity of stomach poisons to slugs
Authors: HENDERSON I. F. 
Published: February 2008

SUMMARYA method is described that allows the toxicity of stomach poisons to the grey field slug, Agriolimax reticulatus (Muller), to be measured in the laboratory. The relative toxicities of three commonly used molluscicides, as expressed by the median lethal dose values, were: sodium pentachlorophenate most toxic with a median value of 22·9 ± 2·5 μg/slug, metaldehyde next with one of 85·2 ± 4·0 μg/slug, and copper sulphate least toxic with one of 129·2 ± 5·9 to 131·6 ± 5·6 μg/slug. The technique allows a given dose of any poison, however repellent, to be administered, but does not measure the repellency or attractiveness.
Population fluctuations of Heterodera rostochiensis Woll. when susceptible potato varieties are grown continuously
Authors: JONES F. G. W. , PARROTT D. M. 
Published: February 2008

SUMMARYWhen seven potato varieties susceptible to Heterodera rostochiensis were grown every year on the same small plots for 6 years with precautions to minimize soil movements, yields were inversely proportional to the number of larvae in the soil before cropping in the first year only. With all the varieties, numbers of larvae after harvest fluctuated around mean values and the fluctuations became smaller in successive years. Although conditions from year to year were as uniform as possible, there were differences in weather, incidence of potato blight (Phytophthora infestans), seed size and quality, and in planting dates. Analysis of soil temperatures and of heat accumulation did not suggest that conditions after planting caused the fluctuations. The smaller fluctuations with repeated cropping probably reflect the influence of population density on the size of the root system and are what would be expected from the curve relating pre‐ to post‐cropping numbers, which reaches a maximum before the reproductive rate decreases to unity.A resistant potato hybrid ex andigena, also grown every year, usually outyielded the susceptible varieties and, by the sixth year, yielded at least twice as much as the mean of the six susceptible varieties.
Some effects of suction on the hatching eggs of Meloidogyne javanica
Authors: BAXTER R. I. , BLAKE C. D. 
Published: February 2008

SUMMARYDevelopment and hatch of eggs of Meloidogyne javanica was independent of suction between pF o and 3·6 but decreased rapidly between pF 3·6 and 4·2. Water was lost from the extracellular fluid of eggs containing developing embryos when the suction was above pF 3·6, causing a decrease in the mean volume of the eggs. The vitelline membrane of an egg is probably semipermeable and the osmotic pressure of the contents about 4 atmospheres (pF 3·6). The volume of the cellular contents of an egg did not increase during development and so the hydraulic conductivity of the soil is probably unimportant in hatching.The results suggest that eggs of M. javanica hatch over a wide range of soil moistures. The inhibition of hatch at high suctions, involving the reversible removal of water, is a likely survival mechanism.
Evidence that toxins are not the causal factors of the specific apple replant disease*
Authors: SAVORY B. M. 
Published: February 2008

SUMMARYExperiments were made to test the hypothesis that a toxin produced by or from apple roots is the causal factor of specific apple replant disease. In sand and vermiculite culture, apple leachates were not harmful to the growth of apples. In the field, apples exerted no effects on neighbouring apples other than competition effects. In pot and field experiments, the addition of apple root residues to fresh (unused) or fumigated soil depressed the growth of both apple and cherry test plants; similar additions to used (‘replant’) apple soil, however, improved the growth of apple, but not of cherry, test plants. It is concluded that specific apple replant disease is not caused by a toxin derived from root residues. It is suggested that the cause may rather be a rhizosphere microorganism.
The significance of temperature during sporulation on the biology of pycnidiospores of Mycosphaerella ligiilicola
Authors: BLAKEMAN J. P. , FRASER A. K. 
Published: February 2008

SUMMARYThe germination, infectivity and survival of pycnidiospores obtained from cultures of Mycosphaerella ligulicola grown at 15 and 26 °C were compared. Spores formed at 26° (‘26° spores’) were less able to germinate at low relative humidities and showed a narrower temperature range for maximum germination after 6 h. At high spore densities 26° spores showed self‐inhibition of germination and, over a range of lower densities, growth of their germ tubes was checked, which resulted in lower infection of leaf discs compared with 15° spores in which this phenomenon did not occur.The fungus could be recovered from un‐sterile compost over a longer period after inoculation with 15° spores. Only after storage at a temperature well below zero was there a difference in viability between 15° and 26° spores.It is thought that the potential advantage of producing larger numbers of spores at 26° would be realized only under optimum conditions for dispersal and infection. The smaller number of spores produced at 15° are likely to be successful under natural conditions.
Biochemical studies on plant tissues infected by Phytophthora palmivora (Butl.) Butl.
Authors: AKINREFON O. A. 
Published: February 2008

SUMMARYLesion formation in tomato and eggplant fruits infected by Phytophthora palmivora could be classified into three phases associated with changes in hydrolytic enzymes in the tissues. Phenolase, arabinofuranosidase and endo‐polygalacturonase activities were all higher than in healthy tissue. The enzymic effects seemed to be reflected in a fairly high loss of pectic materials in the infected tissue, especially the water‐insoiuble components. There was a significant negative correlation (r = ‐0·56) between pH of tomato and the endo‐polygalacturonase secretion in the infected tissues.Paper chromatographic analysis of host metabolites showed little or no qualitative differences between the sugar contents of healthy and of infected tomato tissues; there were also no qualitative differences in the amino acid and the phenolic contents. Chlorogenic acid was detected in healthy but not in infected eggplant tissues and lesion maturation was associated with its disappearance. Gradual browning of the lesion was probably also associated with changes in cell membrane permeability of infected tissue.
Factors affecting aphid infestation of chrysanthemums
Authors: Wyatt I. J. 
Published: February 2008

SUMMARYLarge differences exist between chrysanthemum cultivars in their susceptibility to attack by Myzus persicae (Sulz.). This is due to a repellent factor which increases in the leaves as they age, but which varies from one cultivar to another. Aphid population growth is retarded, or even prevented, on resistant cultivars. If susceptible and resistant plants are in contact, the rate of population increase will be the same on both, but numbers will remain proportionately lower on the resistant cultivars. For instance, aphid numbers are normally forty times as high on B.G.A. Tuneful as on Portrait.Aphids appear to select the cultivar or region of plant most suitable for reproduction (usually apical and basal leaves) but, as the plants and population grow, the aphids continually redistribute themselves. Within the limits of normal growing practice, cultural and environmental conditions have little effect on the aphids. Brachycaudus helichrysi (Kaltenbach) and Aphis fabae Scop, have similar varietal preferences but, unlike Myzus persicae, they avoid senescent leaves and only colonize the apex.