bluuebunny/crossref_metadata_2025_split huggingface dataset:
The determination of irregularly‐shaped areas of leaves destroyed by chewing insects
Authors: BENJAMIN D. M. , FREEMAN G. H. , BROWN E. S. 
Published: February 2008

SUMMARYThe available methods for determining leaf area are briefly reviewed: it is concluded that the most satisfactory method for determining the irregular areas of leaves eaten by chewing insects is likely to be the dot‐grid method. This method has been used: (i) to determine the areas of circular plastic discs of known area; (ii) to determine the areas of tea leaves eaten by various species of adult weevils; (iii) to determine the areas of pieces of maize leaf eaten by larvae of the armyworm, Spodoptera exempta (Walker).For each determination it was found that reliable estimates could be obtained by taking four counts when the number of dots to be counted is between ten and forty, and two counts for larger areas. Dots on the boundary are counted as 0·5. For areas including fewer than ten dots it is usually necessary to use a grid with dots half the distance apart. For armyworm larvae on portions of maize leaf, half the counts should normally be taken vertically and half diagonally to the venation of the leaf; however, for long, thin, uneaten portions of leaf, especially when straight‐sided, vertical counts are too variable, all the counts should be diagonal.
Laboratory experiments on sugar‐beet downy mildew (Peronospora farinosa)
Authors: BYFORD W. J. 
Published: February 2008

SUMMARYThe optimum conditions for Peronospora farinosa betae to produce spores were temperature 8–10 °C and relative humidity 90 % or more, but many spores were produced between 5 and 20 °C and between 80 and 90 % R.H. Most spores were formed in darkness after leaves were exposed to light for 6–8 h. Spores survived exposure to 60 % R.H. for up to 5 days, but were soon killed by temperatures above 20 °C. The germination capacity of spores collected from the field was often very small, but this could not be related to the weather. Most seedlings were infected when inoculated at the growing point and incubated in a saturated atmosphere between 3 and 15 °C for at least 8 h.
Broad‐bean stain and true broad‐bean mosaic viruses
Authors: GIBBS A. J. , GIUSSANI‐BELLI GISELDA , SMITH HELEN G. 
Published: February 2008

SUMMARYAutumn‐sown crops of broad beans (Vicia faba L.) in England often contain plants with some leaves characteristically distorted and with a chlorotic mosaic. From some of these plants true broad‐bean mosaic virus was isolated in 1959 and 1960 but not in 1965 and 1966. From other plants a similar but distinct virus, which caused staining of the seeds and we call broad‐bean stain virus, was isolated in 1960, 1965 and 1966. The two viruses were readily distinguished in serological tests, and in some test plants. Both were seed‐borne, and spread in crops, but were not transmitted by several animal species tested as vectors.Both viruses have isometric particles about 25 mμ in diameter. Some of these particles contain about 35% ribonucleic acid, some about 26% and some of those of broad‐bean stain virus contain none; these three types of particles had sedimentation coefficients of about 120–130 S, 100 S and 60 S respectively. The ribonucleic acid of each virus had molar base content of G 23%, A 26%, C 18% and U 32%.These two viruses are members of the cowpea mosaic group of plant viruses; broad‐bean strain virus was serologically related to cowpea mosaic, F I, red‐clover mottle, and squash mosaic viruses. The particles of all these viruses and of true broad‐bean mosaic virus were similar in appearance, sedimentation behaviour, and nucleic acid content and composition. The nucleic acid of red‐clover mottle virus had a molar base content of G 20%, A 29%, C 20%, U 30%.
The effects of gibberellic acid and nutrient sprays on growth and yield of brussels sprout
Authors: SELMAN I. W. , BORA P. C. 
Published: February 2008

SUMMARYYoung plants of brussels sprout, cv. Cambridge Special, growing in pots in a glasshouse, were sprayed on ten occasions with gibberellic acid (GA) at 0, 25, 100 and 400 p.p.m. and ammonium nitrate (NH4NO3) at 0, 0·0125, 0·025 and 0·05 M concentrations in all combinations. In 24 days both GA and NH4NO3 increased leaf area, leaf number, dry weights of leaf, stem and root, and fresh weights of leaf and stem. GA increased stem height and decreased fresh weight/unit leaf area (leaf thickness), whereas NH4NO3 did not affect stem height and increased leaf thickness. Of the GA treatments, 100 p.p.m. gave the largest plants as judged by fresh weight of the whole plant and leaf area, and of the N treatments 0·05 M NH4NO3 increased growth most. The best treatment combination was 0·05 M NH4NO3 with 100 p.p.m. GA, which gave the greatest fresh and dry weights of the whole plant, leaf area and leaf dry weight as well as increasing leaf thickness. Significant interactions were found between GA and N for dry weight of leaf, fresh and dry weight of root, and leaf thickness but not for leaf area or stem growth (fresh weight, dry weight, height). The combination of levels of GA and N that can be expected to increase leaf area, leaf dry weight and leaf thickness simultaneously, may lie within narrow limits for a particular crop.In a second experiment plants were sprayed with all combinations of GA (0 and 100 p.p.m.) seven times under glass in pots and ten times in the field, and three levels of KH2PO4 on twelve occasions in the field. Sprouts (axillary buds) were harvested in October and February. At the first harvest GA did not affect fresh weight or number, but increased both the total number of sprouts picked (with GA = 80·7; without GA = 69·8 per plant) and the total fresh weight of saleable sprouts (with GA = 2·59; without GA = 2·33 lb/plant). KH2PO4 also increased the weight and number of sprouts at the final harvest and the number of small sprouts at the first. There were interactions between GA and KH2PO4 (P= < 0·001) for both tota weight and number of saleable sprouts.
Comparison of some apple latent viruses
Authors: CROPLEY R. 
Published: February 2008

SUMMARYApple latent viruses were eliminated from, the tips of apple shoots by exposure to a temperature of 36 °C for various periods. The length of treatment needed to eliminate a particular virus differed from plant to plant, but viruses were always inactivated in the same order: first chlorotic leaf spot, followed by stem pitting and finally Spy decline. Quince plants developed sooty ring‐spot and bark necrosis when inoculated with buds from some heat‐treated apple clones infected with Spy decline virus. Only chlorotic leaf spot virus was transmitted to herbaceous hosts by sap extracts from apple leaves, petals and fruits, and returned from herbaceous plants to apple. This virus, isolated from either apple or cherry, caused a dark green mottle on peach leaves.
The influence of foliar applications of sugars on the susceptibility of sugar beet to downy mildew
Authors: RUSSELL G. E. 
Published: February 2008

SUMMARYSpraying sugar‐beet seedlings in the glasshouse, with 1% or 10% solutions of sucrose, 24 h before inoculation with Peronospora farinosa, significantly reduced their susceptibility to downy mildew. The proportion of inoculated plants that became infected was reduced by spraying with sucrose but the main effect was the inhibition of sporulation. Applications of glucose or fructose also increased the resistance of beet seedlings to P. farinosa. Spraying with sucrose 1 or 2 days before inoculation was much more effective than was spraying shortly before inoculation, or 24 h afterwards, or adding sucrose to the inoculum. Washing sucrose‐sprayed seedlings with distilled water 1–2 h before inoculation removed only part of the effect of sucrose on sporulation.Although the mechanism by which applications of sugars affected susceptibility to downy mildew is not understood, the results suggest that the main effects occurred inside the host plant rather than externally. The possible significance of these results, in breeding for resistance to downy mildew and in the control of this disease in the field, is discussed.
Overwintering of Sphaerotheca mors‐uvae on black currant and gooseberry
Authors: MERRIMAN P. R. , WHEELER B. E. J. 
Published: February 2008

SUMMARYThe ability of Sphaerotheca mors‐uvae to perennate as cleistocarps, and as mycelium in buds was examined during the winters of 1965‐6, 1966‐7 and 1967‐8 in relation to its two principal hosts, gooseberry and black currant.Cleistocarps on black currant leaves were examined from August 1965 to April 1966 and from July 1966 to March 1967. In 1965 cleistocarps were first observed on the leaves on 5 August; in 1966 on 11 July. These continued to develop through August and September and by October approximately 70% contained well‐defined ascospores. The ascospore content remained generally at this level until February 1966 and November 1966; then the numbers of cleistocarps with ascospores fell and by April 1966 and March 1967 few such cleistocarps remained. From 21 March 1966 and 15 February 1967, but not otherwise, discharge of ascospores from the overwintered cleistocarps was readily obtained in laboratory tests. The viability and infectivity of the ascospores was demonstrated by allowing them to discharge on to leaf discs of black currant in the laboratory and also on to leaf discs and plants in the field. Sporulating colonies of S. mors‐uvae developed within 8 days.Cleistocarps from shoots of black currant were examined from 4 August 1966 to 9 March 1967, and from 27 July 1967 to 1 January 1968. They developed in a similar manner to those on black currant leaves and by September in both 1966 and 1967 over 60% contained ascospores. This level was not maintained; the number of cleistocarps with ascospores fell gradually and by 8 December 1966 and 1 January 1968 few remained. Only in one laboratory test (21 November 1967) were ascospores discharged from a sample of these cleistocarps.Cleistocarps from shoots of gooseberry were examined from July 1966 to March 1967, and from August 1967 to January 1968. The pattern of ascospore development and subsequent decline in number of cleistocarps with ascospores was similar to that observed for black currant shoots. No discharge of ascospores could be demonstrated in laboratory tests.Evidence that S. mors‐uvae perennates in buds of gooseberry was obtained by dissecting buds and by inducing buds on surface‐sterilized shoots to burst under conditions which precluded chance infection. Field observations also suggested that bud infection occurred on gooseberry. Similar experiments failed to demonstrate the fungus in buds of black currant, and there was no indication of bud infection of this host in the field.
The life‐history and epidemiology of American gooseberry mildew on black currants
Authors: JORDAN V. W. L. 
Published: February 2008

SUMMARYIt is shown that conidia of Sphaerotheca mors‐uvae (Schw.) Berk, from gooseberry readily infect black currant; therefore it is unlikely that a new race of S. mors‐uvae specifically pathogenic to black currants has recently appeared. However, the life‐cycle on black currants differs from that on gooseberry. Incubation, infection and sporulation of the fungus have been examined under the optimum conditions of 18 °C and 100% relative humidity. The establishment of infections and sporulation was encouraged by a relatively low soil moisture content, temperatures above 15 °C, 60% relative humidity and good illumination‐factors which promote vigorous plant growth. High phosphorus and high potassium nutrition also increased the susceptibility of black currants to infection.
Some host‐plant factors affecting oviposition by aphidophagous Syrphidae (Diptera)
Authors: CHANDLER A. E. F. 
Published: February 2008

SUMMARYAlthough most aphidophagous syrphid species lay their eggs close to aphids, Platycheirus peltatus (Meig.), Melanostoma scalare (F.) and M. mellinum (L.) laid freely on uninfested brussels sprout plants. The existence of species that will lay in the absence of aphids may be valuable in biological control and also provides a useful tool for the investigation of non‐aphid oviposition stimuli.Plant species and plant appearance were both important factors in P. peltatus oviposition. Particular sites on the plant were chosen for oviposition by Syrphus balteatus (Deg.). The nature of the substrate at the oviposition site affected the size of the egg batches laid there by M. scalare, M. mellinum, P. peltatus and P. clypeatus (Meig.).The possibility is discussed that plant‐location is the older‐established system of host‐finding and that an aphid‐location system has gradually superseded it during the evolution of the obligatorily aphidophagous Syrphinae.
The interrelationships of the causal fungus of brown root rot of tomatoes and potato root eelworm, Heterodera rostochiensis Woll.
Authors: JAMES GLYN L. 
Published: February 2008

SUMMARYIn a study of the association between the causal fungus of brown root rot of tomatoes and Heterodera rostochiensis Woll., it was demonstrated that the nematode did not increase the susceptibility of the roots to invasion by the fungus; however, the fungus decreased the hatch of the potato root eleworm, the invasion of the host plant by the nematode, and number of new cysts subsequently produced.
Biology and control of the sciarid Lycoriella auripila Winn. (Diptera: Lycoriidae) in mushroom culture
Authors: HUSSEY N. W. , GURNEY BARBARA 
Published: February 2008

SUMMARYThe life‐history of L. auripila, as a pest of mushrooms, is outlined and an explanation is given of the different types of damage caused. The most satisfactory control is based on the incorporation of insecticides in compost at spawning. Emulsions of chlorfenvinphos and diazinon at 50 ppm are lethal to young larvae for at least 7 weeks but granular formulations of the former must be applied at 100 ppm to achieve comparable results. Drenches of 0–01% malathion, applied at about 40 gal/1000 ft2, are effective against larvae in the casing.
The effect of fumigants on soil recolonization in the glasshouse by organisms colonizing the spermosphere
Authors: WATSON A. G. , VAUGHAN E. K. 
Published: February 2008

SUMMARYGerminating turnip seeds were used as baits to measure changes in colonizing floras of the spermosphere in glasshouse soil boxes following fumigation. The spermosphere mycoflora of the untreated soil was always dominated byFusarium, Pythium, andGliocladiumspp. Methyl bromide, chloropicrin, and MBC33(a 67:33 mixture of methyl bromide and chloropicrin), applied in polyethylene bags at a rate of 2·5 ml/cubic foot of soil, greatly reduced colonization byFusariumandPythiumspp. for 120 days. Fungi and actinomycetes recolonizing treated soils were more active than in untreated soils, and each fumigant induced a characteristic recolonization pattern. The spermosphere of methyl bromide‐treated soil was initially dominated by actinomycetes and later byPenicilliumspp. In chloropicrin‐treated soil,Trichodermaand laterPenicilliumspp. dominated, and in soil treated with MBC33,PenicilliumandTrichodermaspp. were co‐dominant. Dilution plates, made at the same time from the same soil, indicated a close correlation between inoculum density of different fungi in the soil and their inoculum potentials towards the spermosphere.
Interactions of the tomato with two formae speciales of Fusarium oxysporum
Authors: LANGTON F. A. 
Published: February 2008

SUMMARYTomato cuttings were inoculated with Fusarium oxysporum f.sp. lycopersici (FL) and F. oxysporum f.sp. pisi (FP) by standing the cuttings in suspensions of bud‐cells of the fungi. FP never induced external symptoms although the fungus persisted in the lower parts of the cutting. FL at concentrations from 103 to 106 spores per ml induced typical wilt symptoms but there was subsequent recovery of some cuttings with the production of uninvaded side shoots.When the cuttings were inoculated with mixed suspensions of bud cells of the two fungi there was marked reduction of symptoms. The extent of this reduction was related to the proportion of FP/FL bud cells for a fixed inoculum of FL in the mixture and was moderate at a rate of 1/3 and complete at ratios from 4/1 to 9/1. Mixed suspensions of heat‐killed bud cells of FP with live bud cells of FL in the ratio of 4/1 induced normal symptoms and it was concluded that the symptom mitigation induced by FP was related to the presence of living cells of the fungus.Root inoculations with mixed suspensions also gave less wilt than with FL alone.Symptom mitigation was apparently associated with a reduction of the extent of invasion of the cuttings but in vitro tests failed to demonstrate that exudates or extracts from normal or invaded tomato tissue induced any reduction of growth of the tomato pathogen.
Association of mycoplasma‐like bodies with potato witches' broom disease from Scotland
Authors: HARRISON B. D. , ROBERTS I. M. 
Published: February 2008

SUMMARYMycoplasma‐like bodies were found by electron microscopy of sections of sieve tubes, both from shoots and roots of potato (Solanum tuberosum) plants affected by Scottish witches' broom disease and from graft‐inoculated tomato shoots. The bodies were bounded by a unit membrane, contained ribosome‐like material and mostly measured 200–800 nm in diameter. Most were oval in cross‐section but some had lobes or slender protrusions. Some of the bodies were found in the mouths of sieve pores.
Effect of main stem number and lateral stem development in potato plants infected with Verticillium albo‐atrum and V. dahliae
Authors: HARRISON J. A. C. , ISAAC I. 
Published: February 2008

SUMMARY‘Early‐dying’ disease was examined in potato plants (King Edward) with varying numbers of main stems and lateral stems. Infection with Verticillium affected neither the number of main stems produced nor the stem number/ lateral number/yield inter‐relationships, but did slightly reduce lateral development. The host growth pattern, however, markedly influenced the severity of disease: infected plants with a single main stem or a few, compared with those having many main stems, showed delayed symptom expression and also produced many laterals which further reduced disease severity and increased longevity. Thus yield reductions as a result of infection are likely to be smaller in single‐stemmed plants showing considerable lateral development than in those plants with many main stems and few or no laterals.
Effects of powdery mildew on cucumber yields, and its chemical control
Authors: SMITH PAULINE M. , READ W. H. , LAST F. T. 
Published: February 2008

SUMMARYEffects of Sphaerotheca fuliginea were deduced from experiments in which cucumber foliage, exposed to naturally occurring inocula, was fungicidally sprayed. Yields increased as the incidence of mildew decreased but the relation was sometimes affected by differing amounts of phytotoxicity.The fungitoxicity and phytotoxicity of a range of chemicals applied as high‐volume sprays, fumigants or soil drenches, were tested. Non‐phytotoxic concentrations of some fungicides adequately protected cucumber foliage from subsequent attack but were often insufficient to eradicate established infections, the increased amounts needed for this being phytotoxic. Powdery mildew was controlled more effectively when drazoxolon and quinomethionate were applied as sprays with 0·1 and 0·02% a.i. respectively, than when used as fumigants at 2–4 and 1·3 g/28·3 m3(= 1000 ft3).Sprays of drazoxolon (0·1% a.i.) increased yields from 7·0 to 11·2 kg/ plant during 8 weeks picking and in another experiment weights of fruit were increased by applying quinomethionate (0·02% a.i.) from 10·8 to 52·2 kg/plot of four plants. In the former experiment appreciable amounts of phytotoxicity and infection were tolerated before yields decreased but, in the latter, yields were inversely proportional to numbers of dead leaves which were directly related to the incidence of mildew. Spraying with quinomethionate, or drazoxolon plus tetradifon (0·012% a.i.) increased numbers of female flowers from 59·5 in the mildewed controls to 93·0 and 142·8 per plant respectively, and of these 17·6, 32·8 and 16·2 % subsequently produced marketable cucumbers.In addition to decreasing yields, severe S. fuliginea infestations were associated with increased numbers of misshapen cucumbers.Increasing sulphur concentrations from 0·5 to 1·0g/28·3m3during nightly fumigations significantly decreased mildew incidence and increased (a) yields from 35·8 to 52·9 kg during 5 weeks picking, and (b) the proportion of high‐quality cucumbers from 49 to 63 %. Similar trends occurred in another trial where sulphur concentrations were increased from 0·75 to 1·0 g/28·3 m3, but comparisons with fortnightly sprays of 0·1% drazoxolon suggest that these sulphur concentrations caused some damage.
Dispersal of conidia of Dothidella ulei from Hevea brasiliensis
Authors: HOLLIDAY P. 
Published: February 2008

SUMMARYSouth American leaf blight caused by Dothidella ulei occurs only in tropical America, on both indigenous and cultivated Hevea spp. The conidium (Fusicladium macrosporum) is a 1‐septate, dry, air‐borne spore about 40 × 7 μ, occurring on the abaxial surface of dry leaves in dense, powdery, olive‐green masses, and with one or both cells collapsed. The conidia adhere to the surface of water droplets, becoming turgid, and are disseminated in splash droplets.A Hirst volumetric trap, placed within a prepared source in north‐west Trinidad, showed a diurnal periodicity of conidial production, with a maximum at 10.00 h and minima at night or in the early morning. On rainless days there was also a minor peak at 20.00 h. Transient increases occurred after rain, most of which fell around noon. On wet days almost equal numbers of conidia were dispersed between 10.00 and 12.00 h. Large increases occurred in 87% of all rain showers between 09.00 and 13.00 h. After 13.00 h fewer rain showers caused such increases; the lowest (36%) was between 21.00 and 01.00 h. Twice as many were trapped on sunny days (> 9 h sun) at 09.00 h when there was full sunshine, compared with overcast days (< 5 h sun). A more clearly defined morning maximum occurred on relatively windy days, compared with calmer ones.Conidial sporulation became very low, or ceased, where rain fell below a mean of 3–4 mm per day for at least 20 days. Abundant sporulation occurred with a daily rainfall about twice this amount. The results support the belief that if Dothidella ulei appeared in Malaysia its spread would be rapid and its effects damaging.
Role of a phytoalexin in controlling lesion development in leaves of Viciafaba after infection by Botrytis spp
Authors: DEVERALL B. J. , VESSEY J. C. 
Published: February 2008

SUMMARYPhytoalexin extracted from infection droplets and diseased tissues behaved as an ether‐soluble acid, and was easily separated by solvent partition from other ether‐soluble substances.The phytoalexin was formed in leaves by apparently healthy cells in advance of hyphae of either Botrytis fabae or B. cinerea, and in response to physical injury. Concentrations of phytoalexin around deep lesions caused by B. fabae were completely fungistatic. B. fabae caused apparent degradation of phytoalexin in lesions, and removed phytoalexin from solutions in vitro much more readily than did B. cinerea.The lower sensitivity to the phytoalexin, and the possibly related greater ability to metabolize the phytoalexin, are major factors in the greater pathogenicity of B. fabae than of B. cinerea. The same properties largely explain the ability of B. fabae to cause the so‐called ‘aggressive’ phase of the chocolate‐spot disease under some conditions.