bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the vapour phase activity of some foliage fungicides
Authors: HISLOP E. C.
Published: February 2008

By means of a Botrytis fabae/Vicia faba bio‐assay technique it has been demonstrated that phenyl mercury chloride, maneb, mancozeb, dichlo‐fluanid and oxythioquinox protect areas of leaf beyond the visible limits of the fungicide deposits. The evidence suggests that the extended areas of protection are due to the release of fungicidal vapours. For a given dose of mancozeb the area of protection was related to the number of conidia of B. fabae dusted on to the leaves and for a given inoculum density it extended with increasing fungicide dose applied in standard drop sizes. When the same dose of fungicide was applied in increasing volumes of water, producing widening areas of deposit, the area of protection also increased. Fungicide deposits aged on leaves for up to 4 weeks continued to release toxic vapours.

Contact between the fungicides and leaves or between fungicides and spores was not necessary for the demonstration of the phenomenon since vapours diffused from deposits on glass and inhibited the germination of spores in water droplets placed at a distance from the fungicide source. For a given distance separating the fungicide and the spores inhibition increased with increasing fungicide dose. For a standard fungicide dose, inhibition decreased with increasing distances between the fungicide and the spores. The fungicidal vapours inhibited the germination of spores of test fungi other than B. fabae.

The practical implications of these observations are examined in the light of evidence that vapour phase protection can occur on leaves incubated in large cabinets; on leaves pre‐incubated at unsaturated humidities; and on leaves incubated in a moving stream of air.
Effect of soil fumigants on Fusarium wilt and nodulation of peas (Pisum sativum L.)
Authors: EBBELS D. L.
Published: February 2008

Chloropicrin, dazomet, formaldehyde, and D‐D soil treatments all decreased the incidence of Fusarium wilt in a wilt‐susceptible variety of pea grown in wilt‐infested soil, but only chloropicrin and dazomet gave satisfactory control of the disease. All four fumigants decreased root nodulation, but no adverse effects on plant growth were detected. With dazomet, formaldehyde, and D‐D, decreased nodulation is largely attributed to the extra soil nitrogen mineralized, whereas with chloropicrin the almost complete suppression of nodulation probably reflects the lethal effect of this material on the Rhizobium bacteria.
The host range and vector species of viruses from Cola chlamydantha K. Schum., Adansonia digitata L. and Theobroma cacao L
Authors: LEGG J. T. , BONNEY J. K.
Published: February 2008

Seventeen species in the Tiliaceae, Sterculiaceae and Bombacaceae were tested for susceptibility to three virus isolates from naturally infected Cola chlamydantha trees and three from Adansonia digitata trees in Ghana. Seven species of Pseudococcidae were tested as vectors of the six isolates. These studies indicate that the Cola isolates should be classified with cocoa swollen shoot virus and those from Adansonia with cocoa mottle leaf virus.
The transmission of strawberry latent ringspot virus by Xiphinema diversicaudatutn (Nematoda)
Authors: HARRISON B. D.
Published: February 2008

Strawberry latent ringspot virus (SLRV) was found in diseased rose bushes growing in a glasshouse where the soil contained Xiphinema diversicaudatum (Micol). Adult female, adult male and juvenile X. diversicaudatum all transmitted the virus to cucumber seedlings, and nematodes kept without plants for 32 days after acquiring SLRV later transmitted it. When transferred to fresh plants every 2–4 days for 3 weeks, single nematodes transmitted up to three times; one nematode did not transmit until 19 days after the transfers began. One adult X. diversicaudatum, out of 141 tested, transmitted both SLRV and arabis mosaic virus. In all respects X. diversicaudatum behaved as a vector of SLRV as it does as a vector of arabis mosaic virus.
Increased susceptibility of black‐currant bushes to the gall‐mite vector (Phytoptusribis Nal.) following infection with reversion virus
Authors: THRESH J. M.
Published: February 2008

Healthy black‐currant bushes (var. Wellington XXX) and others infected systemically with a virulent strain of reversion virus were exposed equally to infestation by the gall‐mite vector (Phytoptus ribis Nal.). Shoots with malformed leaves caused by mites feeding at the stem apices were virtually restricted to the virus‐infected bushes. Buds infested with mites became rounded galls, which were far fewer and more localized on shoots of healthy bushes than on infected ones.

Similar results were obtained in further experiments with Wellington XXX and seven other varieties. Bushes infected systemically with an avirulent strain of reversion virus developed more galls than healthy bushes, but fewer galls than bushes infected with a virulent strain.

The young buds of virus‐infected bushes were 170 times more susceptible to dispersing mites than those of healthy bushes. The axillary buds of healthy bushes resisted infestation and the apical meristems were virtually inaccessible to mites, whereas the axillary and apical buds of virus‐infected bushes were invaded readily.

An experiment with bushes var. Cotswold Cross that were either healthy or partially or completely infected with reversion virus was retained for two years. Each year there was a relationship between symptom expression and mite infestation; only shoots with chronic virus symptoms developed mite‐affected leaves and numerous galls.

Virus infection increased the vulnerability and accessibility of the apical and axillary buds by decreasing the density of hairs on the stems and leaves. Infected bushes also presented a greater catchment area to dispersing mites and more shoots and buds were available for colonization than on healthy bushes.

The interactions between virus, host and vector are discussed, together with their implications in nature, in experimental design and in disease control.
Experiments on the time of application of insecticide to decrease the spread of yellowing viruses of sugar beet, 1954‐66
Authors: HULL R. , HEATHCOTE G. D.
Published: February 2008

Sprays of demeton‐methyl insecticide decreased the spread of yellowing viruses by aphids in sugar‐beet crops in England. Between 1957 and 1960, when yellows was prevalent, the incidence, assessed as ‘infected‐plant‐weeks’, was decreased by 36–41 % by one spray, depending on when it was applied, and by 55 % by two sprays, giving average yield increases of 1½ and 2 ton/acre of roots respectively. Between 1962 and 1966, when yellows spread less, a spray at the time when growers were advised to spray by the British Sugar Corporation decreased yellows incidence by 37 %, whereas sprays 2 weeks earlier or later decreased it by 24 % and 25 % respectively. Between 1958 and 1966 an annual average of 160000 of the country's 440000 acres of sugar beet has been sprayed, often to control Aphis fabae as well as to check the spread of yellows. A spray gives a profitable yield increase when yellows incidence in unsprayed plots is 20 % at the end of August.
The effects on soil fauna of insecticides tested against wireworms (Agriotes spp.) in wheat
Authors: GRIFFITHS D. C. , RAW F. , LOFTY J. R.
Published: February 2008

The organophosphorus insecticides Bayer 38156 (O‐ethyl S‐p‐tolyl ethyl phosphonodithioate), trichloronate, Stauffer N 2790 (O‐ethyl S‐phenyl ethyl phosphonodithioate), thionazin and fenitrothion were compared with aldrin, dieldrin and γ‐BHC for their effects on soil fauna, particularly wire‐worms, and on crop yields in 1964 and 1965. At 1·5 lb active ingredient/acre, none of the organophosphates had as great an effect on wireworms as an aldrin spray at 2·25 lb a.i./acre or a dieldrin seed dressing at 2·25 lb a.i./acre. Some treatments significantly increased and some significantly decreased numbers of mites and Collembola. Except for Allolobophora chlorotica in plots treated with Bayer 38156, earthworm numbers were greater in plots sprayed with Bayer 38156 or aldrin, or sown with dieldrin‐dressed seeds, than in untreated plots. In May 1964, one month after sowing, untreated plots had significantly fewer plants than plots sprayed with aldrin, trichloronate or Bayer 38156, or sown with γ‐BHC or dieldrin‐dressed seeds, but yields from untreated plots at harvest were high for such a large wireworm population and did not differ significantly from yields of treated plots in either year.

The persistence of thionazin and Bayer 38156 in treated plots was measured by a bioassay using Collembola. Bayer 38156 was detected in plots 1 month after spraying but not after 6 months. Thionazin left detectable residues 1 month after spraying in the two acid plots but not in the two alkaline plots. More frequent samples taken from thionazin‐treated plots in 1965 showed a similar pattern of persistence, and laboratory tests, using soil mixed with various amounts of powdered calcium carbonate, confirmed that thionazin persisted longer in more acid soils.
Pesticides and the soil fauna: effects of aldrin and DDT in an arable field
Authors: EDWARDS C. A. , DENNIS E. B. , EMPSON D. W.
Published: February 2008

Aldrin dust (3 cwt. of 1¼% per acre) or DDT dust (2 cwt. of 5 % per acre) was applied to small plots replicated four times and four plots were untreated. All plots were kept fallow for one year. Soil samples were taken at 2 to 3‐monthly intervals and the fauna extracted by a notation method. The insecticides did not affect Lumbricidae, Enchytraeidae or Nematoda. Nearly 100 species of arthropods were found, and the greatest effects were those of DDT on mesostigmatid mites and of aldrin on entomobryid or isotomid Collembola and on Pauropoda. Most species of Collembola increased in DDT‐treated plots, apparently because mesostigmatid mites were reduced. In terms of biomass Coleoptera and Diptera were most affected. Both insecticides killed more pests than predators or beneficial animals. The effects of the insecticides were greatest during late summer or autumn.
The incidence of virus diseases in the honey bee
Authors: BAILEY L.
Published: February 2008

Chronic bee‐paralysis virus and sacbrood virus occur commonly in apparently normal honey‐bee colonies in Britain. Most sick adult bees not affected by Nosema apis, Malpighamoeba mellificae or Acarapis woodi have chronic paralysis and most dead larvae not affected by micro‐organisms have sacbrood. Both virus diseases are probably limited by hereditary factors, but unknown environmental factors also seem to influence disease. Paralysed bees from Australia, Canada, Eire, Germany and Mexico were found to be infected with chronic paralysis virus.
Some effects of supplying benzyladenine to leaves and plants inoculated with viruses
Authors: ALDWINCKLE H. S. , SELMAN I. W.
Published: February 2008

With tomato spotted wilt virus in petunia leaf strips, N‐6 benzyladenine (BA) was as effective as kinetin in decreasing numbers of local lesions, a result which could not be attributed to an effect on the virus per se. Benzimidazole, adenine and ammonium nitrate were without effect. Benzyladenine was more effective than kinetin when supplied through the petioles of excised whole leaves.

Local lesions and infectivity of TSWV in detached leaves of Nicotiana rustica were decreased by supplying BA before and after inoculation. Lesions and infectivity were also decreased in attached leaves when BA was applied 9 days before inoculation. BA supplied to attached leaves after inoculation increased infectivity.

Supplying BA to the lower leaves of tomato plants before inoculating with TSWV decreased infectivity of unsprayed, systemically infected tip leaves taken as inoculum; BA supplied after inoculation increased infectivity.

Local lesions caused by lucerne mosaic virus in excised leaves of Phaseolus vulgaris were decreased in number by supplying BA.

The effects of pre‐ and post‐inoculation sprays of BA are considered in relation to cell metabolism. Since pretreating leaves with kinins did not prevent infection, it is suggested that those which move freely through plants without adverse effects on normal growth may prove of value in increasing the tolerance of plants to virus infection.
Field experiments on sugar‐beet downy mildew (Peronospora farinosa)
Authors: BYFORD W. J.
Published: February 2008

The numbers of sugar‐beet plants infected with downy mildew in experimental crops increased slowly over a period of 8–15 weeks from late May. Few new infections appeared after the middle of August, although less than half the plants were then infected. Most infected plants recovered, and recovery was most rapid and complete in young plants, irrespective of the weather. Plants infected when young produced small roots, but their sugar content and juice purity at harvest was similar to those of uninfected plants. Plants first infected in late July and early August had the smallest sugar content and most juice impurities.
Host/parasite interaction in blackspot disease of roses caused by Diplocarpon rosae Wolf
Authors: SAUNDERS P. J. W.
Published: February 2008

The utilization of amino acids by Diplocarpon rosae Wolf was investigated and compared with amino acid compositions of leaves of resistant and of tolerant roses. No amino acid appeared to determine resistance of roses to blackspot on a nutritional basis, but phenylalanine marginally increased resistance when taken up by wounded leaves of resistant or tolerant varieties. There is an accumulation of phenolic compounds in response to infection by D. rosae. Most phenolic compounds are toxic to D. rosae in vitro, particularly ellagic acid and p‐coumaric acid, but their presence and quantity in healthy rose leaves could not be related to disease resistance. Inhibition of germination on rose leaves of conidia of the fungus was determined in a manner that suggested production of a phytoalexin. It is suggested that resistance of roses to D. rosae may be related to accumulation of polyphenols and possibly to the production of a phytoalexin.
Studies on the persistence and effects on soil fauna of some soil‐applied systemic insecticides
Authors: Way M. J. , SCOPES N. E. A.
Published: February 2008

Granular formulations of menazon, phorate and thionazin were applied to a sandy loam soil (pH = 6·1)in April and May as in‐row treatments at commercial rates. They were also broadcast and mixed into the top 4 in of soil at concentrations (10 and 250 ppm of dry soil) which simulated the local in‐row concentrations in areas large enough for sampling.

Bioassays showed that 50 % of phorate, thionazin and menazon equivalents had disappeared in about 68, 57 and 23 days respectively from soil treated with 10 ppm of the insecticides. Small residues of the 250 ppm treatments still remained 2 years later. The initial rate of loss of activity of thionazin applied at 250 ppm was much slower than from a 10 ppm application whereas the activities of 250 and 10 ppm of menazon disappeared at similar rates.

Phorate at 250 ppm killed almost all earthworms, Collembola, Acarina, free‐living saprophytic and parasitic nematodes and Protozoa; 10 ppm phorate and 250 ppm of menazon also killed almost all Collembola and Acarina but the menazon was relatively harmless to earthworms. Collembola and mite populations began to increase when residues of phorate and menazon equivalents had decreased to about 2 and 20 ppm respectively, and after 15 months they were similar to those in untreated plots.

The broadcast treatments initially decreased the rate of breakdown of leaf discs put in the soil but, after about 4 weeks, breakdown increased, sometimes above that in untreated plots. This was associated with a large increase in numbers of Enchytraeidae which were apparently unaffected by the insecticides.

Four months after application, 1 lb/acre of phorate and 2 lb of menazon applied in seed drills 2 ft apart were not affecting Collembola in soil between the rows but were still decreasing the numbers within them. In ‐row phorate distributed along a 1·5 in diameter band of soil, 3 in deep, killed Collembola 3 in on either side but not 6 in away. It did not spread upwards in toxic quantities, but after rainfall, sufficient to kill Collembola leached at least 3 in downwards.

We conclude that commercial in‐row applications of chemicals like phorate are most unlikely to harm soil fertility, especially as the leaf‐litter‐destroying function of Collembola and other animals killed by phorate may be taken over by Enchytraeidae.
Studies on the nature of resistance in tomato plants to Verticillium albo‐atrum
Authors: SINHA A. K. , WOOD R. K. S.
Published: February 2008

Extracts of healthy resistant and of healthy susceptible plants of tomato had the same effect on growth of Verticillium albo‐atrum in vitro. Tracheal saps from resistant and from susceptible plants showed no difference in their effect on spore germination and mycelial growth of V. albo‐atrum.

Cuttings from resistant plants, inoculated with V. albo‐atrum and fed with low concentrations of casamino acids, or glucose, at first wilted more than controls but soon recovered. Continuous treatment with dilute ethanol solutions for 2 weeks induced marked wilting in inoculated cuttings of resistant plants: treatment for shorter periods caused less severe symptoms, from which cuttings recovered slowly. Metabolic inhibitors did not break resistance of cuttings, but the pathogen survived longer in cuttings treated with sodium diethyldithiocarbamate, salicylaldoxime or 8‐hydroxyquinoline than in controls.

When one end of segments of stems of resistant plants was inoculated with the pathogen, and 48 h later the uninoculated end was placed near a colony of V. albo‐atrum on agar, growth of the fungus colony towards the stem segment was sometimes inhibited. There was no such inhibition when segments from susceptible plants were used. Both tracheal sap and diffusates from segments of inoculated resistant plants supported less growth of germ tubes of V. albo‐atrum than sap and diffusates from uninoculated plants. These differences were not obtained with the susceptible variety and production of fungitoxic substances in resistant plants after infection is inferred.
The control of re‐invasion by rats of part of a sewer network
Authors: GREAVES J. H. , HAMMOND L. E. , BATHARD A. H.
Published: February 2008

Re‐infestation by rats (Rattus norvegicus Berk.) of a section of a sewer network was studied by recording bait consumption in the manhole chambers for periods up to 18 weeks after each of three attempts to rid the section of rats. The mean rate of increase of the rat population was of the order of 20 % per week both when the section was surrounded by a permanently poison‐baited zone as a barrier against re‐invasion from the connected, still heavily‐infested sewers, and when this barrier was absent. When, however, infestation in the connected sewers was reduced by poisoning, and the poison‐bait barrier was maintained, the mean weekly rate of increase in the section declined to 4·4% and could be attributed substantially to breeding.

It is concluded that the type of poison‐bait barrier used in the present trials is insufficient to prevent invasion of one part of a sewer network from another if the population density in the latter is high.
The effect of pollen grains on infections caused by Botrytis cinerea Fr
Authors: CHOU MYRA CHU , PREECE T. F.
Published: February 2008

The addition of pollen to spores of Botrytis cinerea Fr. in droplets of distilled water stimulates spore germination, growth of germ tubes and lesion development. Aqueous diffusate from pollen is as effective as pollen grains, and frozen pollen is more stimulatory than freshly collected pollen. The presence of pollen grains reduces considerably the number of spores needed to allow infection to occur. The lost germination ability and infectivity of old spores is restored by pollen.

The stimulatory effect of the presence of pollen has been demonstrated both in vitro and on the surfaces of strawberry petals, strawberry fruits and broad bean leaves. Complete removal of the source of pollen, the anthers from strawberry fruits, markedly affected the speed and severity of infections of strawberry fruits. On broad bean leaves the addition of pollen grains to spores induced the development of spreading aggressive lesions.

Preliminary work indicates that the effective principle in pollen is water‐soluble, dialysable and heat‐stable. Although glucose and fructose are important components of diffusate, neither glucose solution nor fructose solution nor a mixture of the two showed as marked effects as did pollen. Orange juice produces similar effects.
The relationship between chemical constitution and antifungal activity in arylhydrazono ‐isoxazolone compounds
Authors: SUMMERS L. A. , BYRDE R. J. W. , HISLOP E. C.
Published: February 2008

From a study of compounds related to the mildew fungicide, 4‐o‐chloro‐phenylhydrazono‐3‐methyl‐5‐isoxazolone, it is apparent that high antifungal activity is associated with the arylhydrazonoisoxazolone structure. Differences in the relative effectiveness of o‐chlorophenylhydrazono‐, m‐chlorophenyl‐hydrazono‐ and phenylhydrazono‐ derivatives against Botrytis fabae on beans and Podosphaera leucotricha on apples may be due to different modes of action. Several possible mechanisms of action are discussed.
The elimination of four viruses from carnation and sweet william by meristem‐tip culture
Authors: STONE OLWEN M.
Published: February 2008

Carnation mottle virus (CarMV), carnation ringspot virus (CRSV), carnation vein mottle virus (CarVMV) and carnation latent virus (CarLV) were all eliminated from both carnation (Dianthus caryophyllus) and sweet william (D. barbatus) plants by meristem‐tip culture. Carnation mottle virus was more readily eliminated from D. barbatus than from carnation. Carnation vein mottle and carnation latent viruses were more readily eliminated from carnation than from sweet william: they are rarely found in carnation but CarVMV is found frequently in sweet william. Carnation ringspot was eliminated equally readily from both hosts.
Groundnut rosette and its assistor virus
Authors: HULL R. , ADAMS A. N.
Published: February 2008

Chlorotic rosette from Malawi (isolate CR1), passed through Stylosanthes gracilis and S. juncea, was not subsequently transmissible from groundnuts (Arachis hypogaea) by Aphis craccivora or A. gossypii, but with S. mucronata transmissibility was occasionally regained after a period of time. Aphid transmissibility was similarly lost after passage of two isolates (a chlorotic rosette from Rhodesia, CR2, and a green rosette from Nigeria, GR) through soybean (Soja max) and after manual inoculation to groundnuts. Groundnut plants that remained symptomless after exposure to rosette infection by aphids often contained a virus that restored aphid transmissibility when introduced into groundnuts containing the vectorless virus from that isolate. Groundnut rosette disease therefore consists of a symptom‐inducing virus that we call groundnut rosette virus (GRV) and a symptomless assistor virus (GRAV) that must be present for aphid transmission. The interactions between the GRV and GRAV of chlorotic and green rosette, and their transmission by different vector races, are described.
The association of Xiphinema diversicaudatum (Micoletsky) with strawberry latent ringspot and arabis mosaic viruses in a raspberry plantation
Authors: TAYLOR C. E. , THOMAS P. R.
Published: February 2008

An outbreak of strawberry latent ringspot virus (SLRV) in a plantation of Mailing Jewel raspberry coincided with the greatest abundance of the nematode vector, Xiphinema diversicaudatum. Arabis mosaic virus (AMV) was not detected in the crop but was, together with SLRV, in many weed species present. AMV was transmitted through the seed of Poa annua, Capsella bursa‐pastoris and Senecio vulgaris and SLRV through the seed of Mentha arvensis. X. diversicaudatum were more numerous within the rows than between them and vertical sampling showed that most occurred between 4 and 12 in depth in both locations. Monthly sampling showed that egg laying occurred from April to July; populations increased to a peak in late autumn but declined during the winter, resulting in about a twofold annual increase in numbers. Females, males and juveniles transmitted AMV and SLRV to cucumber seedlings, and in the absence of plants the nematode retained AMV for 112 days and SLRV for 84 days.
Wheat bulb fly, Leptohylemyia coarctata Fall., and its effect on the growth and yield of wheat
Authors: BARDNER R.
Published: February 2008

In two experiments done in successive years to compare the growth and yield of Cappelle wheat either protected from or exposed to attacks by larvae of wheat bulb fly, the plots were previously fallowed, but egg laying was prevented on half of each plot by using Polythene soil covers. In the first season wheat was sown at the end of October, November and December and in the second season in late October and in early January, when there were two sowings, one with and one without a spring application of herbicide. The infestation rate was 1·1‐1·7 million eggs per acre, typical of a moderate attack. Larvae had little effect on the yield of October‐sown wheat as the plants had two shoots each when first attacked and few were killed. On plots sown late, yield was decreased by up to 22%, as plants had only a single shoot when attacked and many were killed.

The main effect of wheat bulb fly was to reduce the number of ear‐bearing shoots by killing plants and restricting the production of new shoots. Surviving plants partially compensated by producing more ear‐bearing shoots with heavier ears and slightly heavier seeds than normal.

Killed plants were not distributed uniformly but were often in patches several feet across. Wheat on the attacked plots ripened more slowly and unevenly than on the unattacked plots.

Weather affects the growth of the plants and activity of the larvae and thus partly determines percentage shoot survival.
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

The 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

The 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

Autumn‐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

Young 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

Apple 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

Spraying 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

The 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

It 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

Although 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

In 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

The 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

Germinating 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

Tomato 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

Mycoplasma‐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

‘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

Effects 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

South 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.