bluuebunny/crossref_metadata_2025_split huggingface dataset:
Powdery mildew of tabacco (Erysiphe cichoracearum DC.)
Authors: COLE J. S. 
Published: February 2008

SUMMARYThe natural spread of Erysiphe cichoracearum was assessed weekly on alternate leaves of irrigated and non‐irrigated tobacco plants of Kutsaga 51 variety, grown in field plots in 1962‐63. Leaf area, air temperature and humidity within the plots, relative turgidity of the leaves and soil moisture were also measured.Leaves emerged over a period of 37 days. A minimum of 29 days elapsed between leaf emergence and infection; irrigation lengthened this period by 2–6 days for leaves 2–6 and shortened it by 2–10 days for leaves 10–18. The duration of the initial resistant phase, in leaves at comparable stalk positions, appeared to be directly proportional to the eventual size of the leaves at reaping. Leaves were not infected until they were almost fully expanded.The longest dry period, when most irrigation water was applied, occurred when most lower leaves (2–8) were fully expanded and already infected; upper leaves (10–18)w ere then still expanding and not yet infected. Irrigation increased infection in all leaves; it increased the growth of the pathogen during dry weather and the subsequent susceptibility of leaves that were still actively expanding but not yet infected.Irrigation increased the percentage of susceptible leaf area infected, of intact plants, threefold and that of topped plants ninefold. Topped plants had less infection than intact ones.
Field experiments on the spread of black currant reversion virus and its gall mite vector (Phytoptus ribis Nal.)
Authors: THRESH J. M. 
Published: February 2008

SUMMARYIn two experiments the spread of reversion virus from a row of systemi‐cally infected black currant bushes heavily infested by the gall mite vector (Phytoptus ribis Nal.) was predominantly in the direction of the winds prevailing during the dispersal period. On each side of the sources there was a curvilinear decrease of galled buds and of virus infection as distance increased.In another experiment a central source of mites and virus was surrounded by concentric hexagons comprising alternate rows of healthy and virus‐infected bushes. At leaf‐fall, galls were forty times more numerous on virus‐infected than on healthy bushes; plants in the sector downwind developed the most galls and those upwind the least. On both healthy and virus‐infected bushes in each sector, the incidence of galls decreased with increasing distance from the source. The gradients of infestation were steeper on healthy than on virus‐infected bushes, especially in sectors upwind from the source. In some sectors the infestation gradients were distorted because many of the virus‐infected bushes were so heavily infested that most of the buds became galled. The spread of virus to initially healthy plants decreased from 100 to 75% near the source, to zero at the periphery. More bushes became infected downwind from the source than upwind.In each experiment more bushes developed galls than later produced symptoms of virus infection, the incidence of which was positively correlated with the number of galls recorded the previous winter.
Viruses occurring in white clover (Trifolium repens L.) from permanent pastures in Britain
Authors: GIBBS A. J. , VARMA ANUPAM , WOODS R. D. 
Published: February 2008

SUMMARYTwenty‐five white clover plants were collected along a transect in each of twenty‐six old permanent pastures in Britain and tested for sap‐transmissible viruses. Viruses were identified by the symptoms they caused, by electron microscopy and by serological tests. Of the 683 plants tested 23 % were infected. In order of decreasing incidence the viruses found were: red clover vein mosaic (in 12% of all the plants tested, and in sixteen of the fields); clover yellow vein (9 % of plants, eighteen fields); white clover mosaic (4 % of plants, eleven fields); arabis mosaic (4 % of plants, eight fields); strawberry latent ringspot (1 % of plants, two fields); and tomato black ring (0.1 % of plants, one field). The three most common viruses occurred in all parts of Britain, and were most prevalent in fields where white clover was most abundant; white clover mosaic seemed more prevalent in fields that were both cut and grazed than in those only grazed. Arabis mosaic virus was obtained only from plants in the west and north of Britain.
Verticillium wilt of the hop: fluctuating outbreaks in wilt‐resistant varieties
Authors: SEWELL G. W. F. , WILSON J. F. 
Published: February 2008

SUMMARYNew varieties of hop resistant to progressive Verticillium wilt are now widely grown and generally give acceptable disease control in commercial plantations, but on a few farms their normal high level of resistance is not maintained. The incidence of wilt on one such farm is analysed in detail. At this site wilt was not directly associated with plant death, as it is in a sensitive variety. In a discussion on etiological aspects of wilt in resistant varieties it is concluded that while seasonal fluctuations in disease incidence are influenced by climatic conditions, high mean incidence is related to undefined, intrinsic soil factors. Attention is directed to the analogous forms of disease resulting from host/pathogen interactions in which resistance and virulence are either both high or both low.
The effect of species of Allium on germination in soil of sclerotia of Sclerotium cepivorum Berk
Authors: COLEY‐SMITH J. R. , HOLT R. W. 
Published: February 2008

SUMMARYSixty‐three different plants, from a wide range of families, were tested for their effects on germination of sclerotia of Sclerotium cepivorum. Germination was stimulated only by members of the genus Allium. Water extracts of Allium species also stimulated germination of sclerotia, but extracts of other plants, and a number of nutrient solutions, had little effect. There was no evidence of inhibition of sclerotial germination by plants which failed to elicit a germination response.
A histochemical and electrophysiological study of the action of diazoxon on cholinesterase activity and nerve conduction in ganglia of the cockroach Periplaneta americana L
Authors: BURT P. E. , GREGORY G. E. , MOLLOY FRANCES M. 
Published: February 2008

SUMMARYWhen sixth abdominal or metathoracic ganglia of the cockroach Periplaneta americana L. were irrigated continuously with diazoxon (O, O‐diethyl O‐(2‐isopropyl‐6‐methyl‐4‐pyrimidinyl) phosphate) solution in situ, the log. of the time required to block conduction in certain nerve pathways in the ganglia was directly proportional to the log. of the concentration of diazoxon applied. Inhibition of cholinesterase began peripherally before function was affected, and had begun to affect the neuropile by the time that conduction was first blocked. Longer exposure to diazoxon disrupted nerve function even more, especially in the sixth abdominal ganglion, and inhibited more cholinesterase, but much longer exposure was needed to inhibit nearly all the cholinesterase. Irrigation with saline, begun when block first occurred, failed to restore completely either nerve function or cholinesterase activity.The cholinesterase activity of ganglia from cockroaches treated topically with an LD90 of diazoxon and examined at intervals after treatment decreased steadily to a level similar to that of ganglia treated directly with diazoxon until conduction was just blocked, but rarely became less, even in moribund insects. Nerve function in metathoracic ganglia became badly affected and remained so in all cockroaches that failed to recover, but sixth abdominal ganglia, though usually badly affected for a time, always recovered normal function, even in prostrate cockroaches. The condition of a poisoned insect, therefore, corresponded much more closely to the functional condition of the metathoracic ganglion than to that of the sixth abdominal ganglion.Applying the insecticide close to a ganglion advanced the time of onset of symptoms but affected the final outcome very little.It was calculated that the highest concentration of diazoxon in the haemo‐lymph in contact with the nervous systems of cockroaches treated topically with LDgo's of diazoxon was about 10‐5M.
An analysis of components of wind affecting the accumulation of flying insects near artificial windbreaks
Authors: LEWIS T. 
Published: February 2008

SUMMARYFlying Cecidomyiidae, Mycetophilidae and Aphididae accumulated to leeward of a windbreak of 45 % open area. There were relatively more of these insects in sheltered than in unsheltered air the greater the angle of the incident wind to the windbreak, and the greater the free wind speed. Mycetophilidae and Aphididae accumulated relatively less as turbulence in the free air increased. The accumulation of Mymaridae to leeward of a solid windbreak was affected only by wind speed. No relationship was detected between the accumulation of Psychodidae, parasitic Hymenoptera, Thysanoptera and Staphylinidae and the incident angle of wind, wind speed or turbulence.
The chemical control of chrysanthemum petal blight caused by Itersonilia perplexans Derx
Authors: SMITH PAULINE M. 
Published: February 2008

SUMMARYLaboratory bioassays of fungicides against Itersonilia perplexans showed that disease developed more readily on outer mature chrysanthemum petals than on immature inner florets and that inoculations on floret tips were more successful than on bases. In glasshouse trials, seven of the fungicides tested significantly decreased disease development without inducing phytotoxicity: of these, maneb and mancozeb, but not zineb, left unsightly deposits.Tank‐mixed zineb was more fungitoxic, especially in continuing high humidities, but was also more phytotoxic than wettable powder and dust formulations, but this phytotoxicity could be avoided by spraying the crop at the opening bud stage and by increasing the interval between applications from 5 to 7 days.
The effects of soil moisture at the time potato tubers are forming on the incidence of common scab (Streptomyces scabies)
Authors: LAPWOOD D. H. 
Published: February 2008

SUMMARYTwo complementary field experiments at Rothamsted in 1965, with the potato variety Majestic, related the incidence of common scab (Streptomyces scabies) to rainfall, soil moisture and time of tuber formation.In plots where the soil was maintained at field capacity (less than 10 cm. Hg moisture tension) by watering, tubers had little or no scab; infection increased in amount on plots allowed to dry to 30 cm., 50 cm. or more Hg moisture tension during late June.The time tubers formed was varied by planting sprouted (chitted) and non‐sprouted seed tubers, and tuber development and scab incidence were observed on sample plants lifted at frequent intervals from unwatered plots. Scab lesions were first seen on 12 July when the distribution of lesions on the surface of tubers was affected by size of tuber both within and between the different seed‐tuber treatments. These differences were correlated with estimates of tuber size on 28 June, the beginning of the first dry period. Tubers 1.0 cm. or more in diameter on 28 June had few or no lesions at the stolon attachment (heel) end of tubers on 12 July, whereas tubers smaller than this on 28 June had many lesions in this region on 12 July. The larger the tuber was on 28 June, the greater was the area free from scab lesions on 12 July.
Narcissus mosaic virus
Authors: BRUNT A. A. 
Published: February 2008

SUMMARYNarcissus mosaic virus (NMV) is widespread in British crops of trumpet, large‐cupped and double daffodils, but was not found in Narcissus jonquilla or N. tazzeta. Many commercial daffodil cultivars seem totally infected, and roguing or selection is therefore impracticable. Strict precautions by breeders and raisers to prevent infection of new cultivars is recommended. Healthy daffodil seedlings were readily infected with NMV by mechanical inoculation, but the virus was not detected in them until 17 months after inoculation, when a mild mosaic appeared.NMV infected twenty‐eight of fifty‐three inoculated plant species; only five (Nicotiana clevelandii, Gomphrena globosa, Medicago sativa, Trifolium campestre and T. incarnatum) were infected systemically, and NMV was cultured in these and assayed in Chenopodium amaranticolor and Tetragonia expansa. The virus was not transmitted to and from G. globosa or N. clevelandii by three aphid species, or through the seeds of Narcissus, G. globosa and N. clevelandii but was transmitted by handling. G. globosa sap was infective at a dilution of 10 ‐5 but not at 10‐6, when heated for 10 min. at 70° C. but not at 75° C, and after 12 weeks at 18° C, or 36 weeks at 0–4° C. NMV withstood freezing in infected leaves and sap, and purified preparations and freeze‐dried sap remained infective for over 2 years. NMV was precipitated without inactivation by ammonium sulphate (313 g./l.) but was better purified by differential centrifugation of phosphate‐buffer extracts treated with n‐butanol. Such virus preparations from G. globosa, N. clevelandii, C. amaranticolor and T. expansa were highly infective, serologically active, produced a specific light‐scattering zone when centrifuged in density‐gradients and contained numerous unaggregated particles with a commonest length of 548–568 mμ. Antisera prepared in rabbits had precipitin tube titres of 1/4096. NMV was detected in three experimental hosts but not in narcissus sap. Unlike some viruses with elongated particles, NMV precipitates with antiserum in agar‐gel. Purified preparations reacted with antiserum to a Dutch isolate of NMV but not with antisera to seven other viruses having similar particles and in vitro properties, or to narcissus yellow stripe virus.
Studies on the nutrition of Arthrobotrys oligospora Fres. and A. robusta Dudd: The saprophytic phase
Authors: BLACKBURN F. , HAYES W. A. 
Published: February 2008

SUMMARYGrowth requirements of two predaceous hyphomycetes in the absence of eelworm prey were determined in specified culture media, in an investigation of the interrelationship of eelworm and fungi. Both fungi were able to utilize a wide range of energy sources and gave the highest yields of mycelium when the carbon sources supplied had the same configuration as glucose around carbon atoms, 3, 4, 5 and 6, or were oligosaccharides yielding glucose on hydrolysis. The species differed in their ability to utilize nitrogen sources, A. robusta producing very little growth when nitrate was the sole source of nitrogen, and comparatively little on aspartate nitrogen. Both responded to thiamin, biotin and p‐aminobenzoic acid, but neither species showed absolute dependence on an external source of vitamin.
Effects of temperature and nitrogen supply on the growth of timothy (Phleutn pratense L.)
Authors: SMITH DALE , JEWISS O. R. 
Published: February 2008

SUMMARYTimothy was grown in controlled environments with day/night temperatures of 18.5/10° C. and 29.5/21° C, with and without extra nitrogen. High temperatures hastened all stages of development after inflorescence initiation. Anthesis occurred after 48 days when N was added and after 52 days without N. Anthesis did not occur until after 68 days at the lower temperatures, with or without N.Largest yields of leaves, stems and stubble were produced at all growth stages at the lower temperatures with N. This treatment gave the highest crop growth rate, which increased almost linearly with time. The lower temperatures with N gave many more and longer stems and more inflorescences than any other treatment. With N and high temperatures, there was no increase in crop growth rate after inflorescence emergence. Temperature had little effect on growth when no N was provided. With no added N, crop growth rate was retarded and increased very little after inflorescence initiation.Herbage produced at high temperatures had the lower percentages of water‐soluble carbohydrates and digestible dry matter, but had the higher percentages of most minerals. N increased the percentage content of most minerals.Weights of stubble and of water‐soluble carbohydrates in the stubble, and the numbers of stem bases and tillers, were larger at the lower temperatures, and were usually larger with added N in both temperature regimes. Nitrogen decreased the percentage content of carbohydrates in the stubble. Large haplocorms were produced at the low temperatures, but none developed at the high temperatures, indicating less carbohydrate storage.The results partly explain the vigorous growth of timothy in the cool, temperate regions of Europe and North America, and the small dry matter production, lower nutritional value of the herbage, and lack of persistence in the warm southern regions where rainfall is adequate.
Investigations on fungicides: The systemic fungicidal activity of certain N‐carboxymethyl dithiocarbamic acid derivatives
Authors: HEYNS A. J. , CARTER G. A. , ROTHWELL K. , WAIN R. L. 
Published: February 2008

SUMMARYThe systemic activity of thirty‐three N‐substituted S‐esters derived from dithiocarbamic acid was investigated by assessing their ability to reduce the infection of broad‐bean seedlings by Botrytis fabae and of wheat seedlings by Erysiphe graminis, following application to the roots or cut shoots of the host. Marked systemic activity against mildews was shown by the N‐carboxymethyl dithiocarbamates, by S‐carboxymethyl‐N, N‐dimethyl‐dithiocarbamate (G33) and by procaine and 6‐azauracil. The effect was not very host‐specific since most compounds showing high activity in wheat also showed activity in pea, cucumber and, to a smaller extent, apple. All the materials tested showed a much lower level of systemic activity in broad‐bean seedlings against B. fabae.Measurements were also made of the uptake, translocation, phytotoxicity and the stability within plant tissues of some of these compounds. The degree of systemic activity which they show is discussed in relation to these and other properties of the compounds.
Celery leaf spot: sources of inoculum
Authors: SHERIDAN J. E. 
Published: February 2008

SUMMARYThe relative importance of infected celery seed, infected leaf debris in the soil, and infected wild celery, in the incidence of Septoria leaf spot in cultivated celery has been investigated. Infection can be caused when the sole source of inoculum is viable spores on the seed surface; such spores are considered to be the main cause of disease outbreaks.Of all the seed samples examined, 93% were infected by Septoria spp. In untreated seed samples, 40% carried viable spores which survived for up to 15 months on seed stored in the laboratory, and for longer periods on seed stored at ‐20d̀ C. However, ageing of seed is not recommended as a commercial control measure.The fungus was not found in seed embryos or endosperms but mycelium was present in pericarps and testas. Unconfirmed evidence suggests that in favourable circumstances new spores might be produced in old seed‐borne pycnidia.
The epidemiology of tomato brown root rot
Authors: LAST F. T. , EBBEN MARION H. 
Published: February 2008

SUMMARYIn the absence of nematodes, three different symptoms of disease, parts of the brown root rot complex (BRR), occurred on tomato roots surviving in soils infested with GSF (= grey sterile fungus) and Colletotrichum atramentarium (Berk. & Br.) Taubenh. In heavily infested soils brown lesions occurred throughout cropping, appearing within a week of planting. Corkiness and black dot, caused by GSF and C. atramentarium respectively, rarely occurred until the third month after planting but towards the end of the season the incidence of black dot sometimes suddenly increased greatly.Observations of crops growing in plots treated with different soil partial sterilants suggested that GSF was more damaging than C. atramentarium. Yield was not related to the incidence of black dot but was inversely proportional to the occurrences of brown lesions and corkiness. The relation with brown lesions was significant within 8 weeks of planting, when most brown lesions gave cultures of GSF, but later more of these lesions gave cultures of C. atramentarium than of GSF.Pathogenicity tests with pure cultures of GSF and C. atramentarium were done on agar media and by artificially infesting partially sterilized soils. Roots of undamaged seedlings on agar media developed 10 mm. brown lesions within 2 weeks of inoculating 10‐day‐old tomatoes with most GSF cultures isolated from: (1) rotted roots of Lycopersicon esculentum, Solanum capsicastrum, Capsicum annuum var. longum and C. frutescens; (2) browned zones of Lycopersicon hirsutum roots; and (3) apparently healthy roots of Cucumis sativus. After inoculation with C. atramentarium, small (c. 2 mm.) pink lesions developed, whereas none formed using Pyrenochaeta spp.In soil tests the greater root damage done by GSF, including root loss, was reflected in decreased aerial growth and smaller fruit yields; C. atramentarium affected neither. In the second year of soil infestation GSF decreased yields during 6 weeks of picking from 1.96 kg. in the uninoculated controls to 1.02 kg./plant.The pattern of damage done by GSF changed as plants aged. In soil, brown lesions occurred within a few days of planting but corkiness did not appear for 2–3 months, when stem lesions and leaf yellowing often developed simultaneously. A 50% root loss after 21 weeks did not affect fruit yields whereas a 40% loss within 11 weeks of planting was reflected by a 45% yield decrease.
Influence of cocksfoot streak virus on the growth of cocksfoot swards
Authors: CATHERALL P. L. , GRIFFITHS ELLIS 
Published: February 2008

SUMMARYSmall experimental swards of three types‐healthy, 50% and 100% streak‐virus‐infected‐were established from single tillers of randomly selected cocksfoot genotypes. In these swards 44% of infected plants died within 2 years compared with 21% of healthy plants. Mortality of infected plants was not increased by the presence of healthy plants in the same sward. In swards containing both healthy and infected plants, increased growth of healthy plants compensated for the low yield of infected ones only when the swards were frequently defoliated. Infrequent cutting apparently allowed infected plants to check the growth of healthy ones, and 50% infected swards yielded little more than 100% infected swards. This difference in response was attributed to differences in the growth habits of healthy and infected plants. Few initially healthy plants became infected during 2 years of the experiment.
The effect of certain antibiotics on reproduction of the black bean aphid, Aphis fabae Scop.
Authors: JAYARAJ S. , EHRHARDT P. , SCHMUTTERER H. 
Published: February 2008

SUMMARYThe antibiotic terramycin at 0.2% concentration was consistently effective in greatly reducing the populations of Aphis fabae on Vicia faba when sprayed on larvae on and off the plant. The insects were not killed, but their fertility was decreased by over 97% in the first generation, leading to total sterility in the second generation. At 0.01% concentration, terramycin was not effective and only moderately so at 0.1%Larval development was invariably delayed by 1 day and the weight and size of the resulting adults were significantly reduced. After the most effective treatments, the adults were very inactive in their feeding and excretion, and sometimes became completely sterile. Even when the aphids reproduced, they ceased to do so after 6–10 days in different terramycin treatments and frequently the larvae were born dead. The affected insects could not, apparently, regain their reproductive capacity even after their transfer to untreated plants.When the insects were sprayed on the plants, terramycin in water was as effective as with surfactants: but when the insects were sprayed off the plants an oxyethyl phenol derivative (NP 10) greatly increased the efficiency of terramycin: surfactants alone had no effect on the insects.The other four antibiotics, namely tetracycline, aureomycin, chloramphenicol and reverin were not effective at the 0.2% concentration when the plants alone were sprayed before introducing the apids. The addition of glycerin to the antibiotics and keeping plants in a high humidity for 24 hr. after the treatment also had no effect.