bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions of crop density of field beans, abundance of Aphis fabae Scop., virus incidence and aphid control by chemicals
Authors: WAY M. J. , HEATHCOTE G. D.
Published: February 2008

The number of Aphis fabae Scop. per plant and per acre developing on field beans (Vicia faba L.) was inversely related to seeding rate (i.e. plant density) except sometimes at very low rates; with equal numbers of plants per acre, fewer aphids developed on plants in rows 11 in. than 22 in. apart.

Plots sown in mid‐March with more than about 150,000 plants per acre were more attractive than less dense stands to colonizing alate A. fabae, but established colonies multiplied most on the sparsest and least on the densest plots.

The number of plants per acre infected by pea leaf‐roll virus was inversely related to planting density. There were more virus‐infected plants on II in. than on 22 in. spaced rows‐in contrast to the numbers of A. fabae. A single spray with demeton‐methyl, timed to control A. fabae, did not significantly decrease virus incidence.

Grain yields of sprayed plots were little altered by increasing the seed rate above a critical minimum, except in one year when the densest crops lodged. Increased yields from spraying were closely related to the numbers of A. fabae on unsprayed plots. Dense planting (more than 400,000 plants per acre) prevented or greatly decreased losses caused by A. fabae in unsprayed plots except in one year when the aphids were exceptionally abundant.
Powdery mildew of tabacco (Erysiphe cichoracearum DC.)
Authors: COLE J. S.
Published: February 2008

The 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

In 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

Twenty‐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

New 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

Sixty‐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

When 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

Flying 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

Laboratory 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

Two 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.
Studies on plant growth‐regulating substances: Water uptake by discs from inulin‐storing roots and tubers in response to growth‐substance treatment
Authors: RUTHERFORD P. P. , GRIFFITHS C. M. , WAIN R. L.
Published: February 2008

Discs of tissue cut from chicory and dandelion roots are shown to take up large amounts of water when treated with solutions of the auxin 2,4‐dichlorophenoxyacetic acid. The effects of disc size, concentration of auxin and cold‐storage of the roots on the magnitude of the response have been studied. A range of plant growth‐regulating chemicals has been examined for the capacity to promote water uptake in chicory root discs. The results are considered both in relation to chemical structure and to the growth responses induced by these compounds in the wheat cylinder and pea segment tests. The evidence indicates that the water uptake response by chicory root tissues provides a useful method for assessing plant growth‐promoting activity.
Narcissus mosaic virus
Authors: BRUNT A. A.
Published: February 2008

Narcissus 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

Growth 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

Timothy 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

The 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

The 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

In 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

Small 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

The 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.
Some properties of cocksfoot mottle virus
Authors: SERJEANT E. P.
Published: February 2008

Cocksfoot mottle virus (CFMV) was transmitted by manual inoculation of sap to cocksfoot (Dactylis glomerata L.), wheat, oats and barley, but not to nineteen other monocotyledonous and thirteen dicotyledonous plant species. The virus was also transmitted by cereal leaf beetles (Lema melanopa L.). Adult beetles infected plants more frequently than larvae, and remained infective for up to 2 weeks after they had fed on infected plants. Seed from infected cocksfoot and oat plants produced virus‐free seedlings.

The infectivity of sap was lost during 10 min. at 65° C., and 2 weeks at 20° C., but survived many months at — 15° C.

Purified virus preparations, made by various methods, contained numerous nearly spherical particles, about 30 mμ in diameter. In electron micrographs some of the particles were penetrated by negative stain though most appeared intact. However, all the particles migrated together in a centrifugal (sedimentation coefficient = 118 S) or electrophoretic field. The ultraviolet absorption spectrum, and the phosphorus and nitrogen contents of the virus preparations, were typical of a nucleoprotein containing about 25 % nucleic acid.

Serological tests failed to show any relationship between CFMV and eleven other viruses with particles of similar shape and size.
The transmission of European wheat striate mosaic virus by Javesella pellucida (Fabr.) injected with extracts of plants and plant‐hoppers
Authors: SERJEANT E. P.
Published: February 2008

Virus‐free individuals of the plant‐hopper Javesella pellucida (Fabr.) infected plants with European wheat striate mosaic virus (EWSMV) after being injected at 5° C. with extracts of either plants or hoppers, but extracts of hoppers provided a better inoculum. Hoppers were unable to infect plants until at least 8 days at 20–25° C. after they were injected, and nymphs fed on infected plants similarly required 8 days before they gave infective extracts. Few hoppers survived more than a week after injection with untreated extracts of hoppers or with material sedimented from them by centrifuging the extracts at 8000g, but 60–70% survived injection with purer virus preparations. Injection of the virus seemed harmless, because as many hoppers survived CO2 anaesthesis + injection, whether or not they later infected plants, as survived anaesthesis without injection. Attempts to determine the properties of the virus in vitro gave inconsistent results, but virus from hoppers was still infective after 10 min. at 30° C, 36 hr. at 5° C, precipitation at pH 4.0, storage for several months at ‐15° C, or at a dilution equivalent to 0.0014 g. hopper/ml. The best extraction medium contained 0.2 M‐Na2HPO4+ ascorbic acid + 0.01 M‐DIECA at pH 7.0–7.3. In sucrose density‐gradients, EWSMV sedimented more slowly than tobacco mosaic virus. No specific particle with which infectivity could be correlated was seen by electron microscopy.
The significance of biological races of Ditylenchus dipsaci and their hybrids
Authors: WEBSTER J. M.
Published: February 2008

Pure cultures of six races of Ditylenchus dipsaci derived from a single female, namely, lucerne race (LR), red clover race (RCR), white clover race (WCR), narcissus race (NR), tulip race (TR) and oat race (OR) were inoculated into eight plant species growing in pots. Onion was host to all six races, and tulip to all except RCR, whereas lucerne was susceptible only to LR and slightly to WCR. Hyacinth was not very susceptible to any race. The TR and OR were the most polyphagous. Severe symptoms were not necessarily associated with large nematode populations. Parthenogenesis did not occur. Ten fertile hybrids between races were produced and the host range of five of these was tested. On average the hybrids multiplied less than their parent races and their host ranges showed no relationship to those of their parent races. RCR and TR inoculated together into tulip produced significantly fewer nematodes than did TR alone and more than RCR alone. Mixed populations of races occur in nature which are probably a mixture of parental races, their hybrids and back‐crosses. Repeated back‐crossing of the hybrids with parental types and the slower multiplication of the hybrids is an explanation for the variation in host range of known races and the failure to record new races.
The uptake and adsorption of diquat and paraquat by tomato, sugar beet and cocksfoot
Authors: BRIAN R. C.
Published: February 2008

Experiments on leaves of tomato, sugar beet and cocksfoot show that uptake of diquat and paraquat, although rapid in the light, is increased by darkness and therefore takes place through the cuticle and not through stomata. Darkness for as little as 4 hr. increased uptake almost twofold.

Diquat and paraquat are rapidly and strongly adsorbed both to leaf tissue and to extraneous matter on the leaf surface.

Uptake in the field is so rapid that rain immediately after treatment has little adverse effect.
Bacterial canker of poplars in Britain: The cause of the disease and the role of leaf‐scars in infection
Authors: WHITBREAD R.
Published: February 2008

Bacterial canker and die‐back of poplars in Britain is caused by Aplano‐bacterium populi Ridé. Pseudomonas syringae (van Hall), which has been suggested as the causal agent, plays at most only a minor role in canker lesions. It may cause a shoot blight in spring, a distinct pathological condition frequently associated with bacterial canker.

Marked variation in infectivity of bacterial slime between seasons and at different dates of collection within one year appears to be the main cause for situations in which varieties, resistant in trials to inoculation with slime, have proved susceptible in the field.

Leaf scars afford the main avenues for infection but their infectibility declines rapidly during October. The implications of the temporal separation of availability of natural inoculum and available infection sites are discussed.
Dothistroma needle blight of pines: Effect and etiology
Authors: HOCKING D. , ETHERIDGE D. E.
Published: February 2008

The defoliating needle blight of pines caused by Dothistroma pini Hulbary (perfect state Scirrhia pini Funk & Parker) is severely damaging to plantations of Pinus radiata D. Don., P. ponderosa Laws, and P. nigra Am. Symptoms and studies on P. radiata are reported.

Disease severity has a linear relationship to stunting in very young trees, and a sigmoidal relationship to losses of height and diameter increments in 3‐year‐old trees, the most rapid losses occurring at disease severities between 25 and 75% blighted foliage. Height, independently of age, reduces disease severity. Maximum infection occurs at 0–5 ft. above ground level, while above 18 ft. there is significantly less attack.

Rainfall of less than 1/2 in. weekly has little effect on disease increase and a mean weekly temperature of 65° F. or greater seems to be necessary for large disease increases; but the general environmental relations are too complex to be explained entirely quantitatively from the present data.
Susceptibility of potato tubers to infection by Phytophthora infestans
Authors: LACEY J.
Published: February 2008

Phytophthora infestans infects King Edward potato tubers more readily through inoculated eyes than through lenticels, but more lenticels than eyes became infected when whole tubers were sprayed with inoculum. The resistance of lenticels but not of eyes increased as tubers aged. The spores did not infect through intact periderm. The likelihood of tubers on plants grown in pots becoming infected by sporangial suspension poured on to the soil increased the nearer the tubers were to the soil surface, the stem, or the side of the pot. Naturally infected tubers, and those sprayed with sporangial suspension, had most eyes infected at the rose end, and most lenticels infected on the middle region of the tuber. Of naturally infected tubers, on which the site of infection could be identified, most were infected through eyes at the rose end.
The multiplication of Longidorus elongatus (de Man) on different host plants with reference to virus transmission
Authors: TAYLOR C. E.
Published: February 2008

In pot tests, Longidorus elongatus (de Man) populations increased rapidly on Fragaria vesca, Stellaria media, Mentha sativa and Lolium perenne and slightly on Brassica rapa (turnip var. White globe) and on Ribes nigrum; but on Rubus idaeus populations declined at the same rate as in fallow soil. Raspberry ringspot (RRV) and tomato black ring (TBRV) viruses were readily transmitted by L. elongatus to S. media, TBRV only was transmitted to L. perenne, and M. sativa became infected with neither virus. RRV was transmitted to R. idaeus var. Mailing Jewel, on which the nematode fed but evidently did not reproduce.

In a field experiment L. perenne and Fragaria ananassa (strawberry) vars. Huxley and Redgauntlet were shown to be good hosts for L. elongatus and R. idaeus (raspberry) vars. Lloyd George and Mailing Jewel were confirmed as non‐hosts, together with Rheum rhaponticum (rhubarb). Two periods of egg laying were detected each year in the Redgauntlet strawberry plots and these coincided with the growth of young roots during the late spring and autumn.

The wide host range of L. elongatus among cultivated plants and weeds, together with its ability to survive long periods without food, precludes the use of crop rotation as a means of control. Chemical soil sterilization is considered the most effective means of control because it can greatly decrease L. elongatus populations and as the nematode multiplies slowly, even on favourable host plants, several years are likely to elapse before populations become large enough to spread viruses effectively from infector plants to susceptible crops.
Soil teachings and the hatching of larvae of the potato‐root eelworm, Heterodera rostochiensis Wollenweber
Authors: ELLENBY C. , SMITH L.
Published: February 2008

Leachings were taken from fallow soil brought in from an outside plot at monthly intervals throughout a year, and tested for their ability to stimulate hatching of the potato‐root eelworm. Some of the leachings showed stimulatory action, the results indicating a seasonal pattern of activity with a peak in August. As noted previously, this suggests that soil organisms produce substances able to stimulate hatching and that these are probably responsible for the so‐called ‘spontaneous’ hatching.
Selection of aphid prey by Adalia bipunctata L. and Coccinella 7‐punctata L
Authors: BLACKMAN R. L.
Published: February 2008

Larvae and adults of Adalia bipunctata L. and Coccinella 7‐punctata L. seemed unable to detect and avoid feeding on unsuitable or toxic aphids, e.g. larvae of A. bipunctata fed on the highly toxic Megoura viciae, even when given the choice of a suitable aphid. Apparent preferences were not always for the most suitable food.

Field cage experiments demonstrated the preference of adult A. bipunctata and C. 7‐punctata for different habitats, the former ovipositing at the shrub level (4 ft.) and the latter feeding and ovipositing on plants near ground level.
Dothistroma needle blight of pines
Authors: HOCKING D.
Published: February 2008

In laboratory and field tests against Dothistroma pini of thirty‐eight commercially available or experimental fungicides several showed high contact activity (notably Blasticidin M), indicating potential eradicant properties. Only triphenyl tin or copper‐based compounds gave good field protection.

For protection, two widely spaced annual applications are recommended for an area with two heavy rainfall periods.
Biochemical changes in infection droplets containing spores of Botrytis spp. Incubated in the seed cavities of pods of bean (Vicia faba L.)
Authors: DEVERALL B. J.
Published: February 2008

Infection droplets containing spores of Botrytis cinerea become inhibitory to the growth of germ tubes of the fungus within 18 hr. of their incubation in bean pods. The inhibition is caused by an ether‐soluble substance, which has been partially purified, and which counteracts the stimulatory effect of sucrose, glucose, fructose, galacturonic acid and several amino acids, which are also present in the infection droplets.

Changes in concentration of these substances have been described in the first 24 hr. after placing infection droplets in pods. The only major difference between droplets containing B. fabae and B. cinerea concerns the nature of the ether‐soluble substances produced. Following B. fabae infection a biologically inactive u.v. absorbing substance appears in high yield in place of the antifungal substance formed following B. cinerea infections.
The use of heat to control the rotting of Cox's Orange Pippin apples by Gloeosporium spp
Authors: EDNEY K. L. , BURCHILL R. T.
Published: February 2008

Dipping in warm water successfully reduced the incidence of infection of Cox's Orange Pippin apples by Gloeosporium spp. Treatment of fruit loaded after harvest with spores of G. perennans was most successful if carried out 3–9 days after inoculation; later treatment was less effective. Infection taking place late in the growing season was relatively more susceptible to treatment than infections established on less mature fruit. Steam/air mixtures provided a successful, alternative source of heat; accelerated cooling after treatment with such mixtures did not reduce their effect. Browning of the skin and increased incidence of rotting by Penicillium spp. may follow heat treatment. With liquid cultures heat has a greater effect on germinated than on ungerminated spores and over the range of temperatures used for treating apples results in delayed fungal development rather than eradication.
Inheritance of resistance in maize to the virus of streak disease in East Africa
Authors: STOREY H. H. , HOWLAND AUDRIE K.
Published: February 2008

Maize plants selected from lines raised in South Africa, and resistant to an East African isolate of streak virus, gave rise on selfing to lines that bred true for resistance through four generations.

Heterozygotes from crossing resistant by susceptible lines reacted to infection by inoculation with the vector in a manner intermediate between the parents; neither allelomorph was fully dominant. The F2 generation from the cross segregated in the expected 1:2:1 ratio. Backcrosses segregated 1:1.

The evidence is interpreted as showing control of resistance by a major gene, but with modification in details of the reaction attributed to minor genes.
Some effects of cultural treatments on virus diseases of cultivated mushroom, Agaricus bisporus
Authors: LAST F. T. , HOLLINGS M. , STONE OLWEN M.
Published: February 2008

Inoculating crops of a white strain of mushroom with virus‐infected cultures delayed cropping and decreased yields; the effects were progressively less the later that infection occurred, and/or the larger the amount of healthy spawn used.

Crops in trays inoculated at a single site usually developed three zones: (1) a barren zone about the site of inoculation, progressively enlarging as the crops aged; and surrounded by (2) a band of stunted mushrooms bordering an outer area (3) of apparently healthy crop, in which a few sporophores might show hard‐gill or watery‐stipe abnormalities. Mycelial isolates taken at different distances from the sites of inoculation grew at different rates, growth being inversely proportional to the virus content of the fruit‐bodies as estimated by electron microscopy and serology. Isolates from virus‐free mushrooms grew rapidly on agar media, producing white fluffy colonies with many coarse strands, whereas those obtained from the few fruit‐bodies near sites of inoculation were brown, adpressed to the medium, and grew very slowly. Between these extremes a continuous range of intermediates occurred, most of which remained constant when subcultured. Isolates taken at successive intervals from the same site in a tray had progressively smaller growth rates.

Unsterilized mushroom‐growing equipment (e.g. trays) is thought to carry viruses in infected spores and mycelial fragments which infect later crops without inducing characteristic zones. Instead, cropping of the whole tray declines with each successive flush. Such infection was prevented by heat‐sterilizing the trays between crops.
Persistence and distribution of insecticidal seed‐dressings for control of the wheat bulb fly, Leptohylemyia coarctata
Authors: LORD K. A. , SCOTT G. C. , JEFFS K. A. , GRIFFITHS D. C. , MASKELL F. E.
Published: February 2008

Samples of plants and soil from two experimental sites, one clay loam and one peaty loam, were analysed chemically to try to explain differing results with γ‐BHC and dieldrin seed‐dressings applied to control wheat bulb fly on different soil types, and to suggest reasons for patchy plant stands and occasional failure to control the pest. Seed dressed with dieldrin yielded more than untreated seed on both sites, whereas seed treated with γ‐BHC yielded as much as seed treated with dieldrin on the clay site, but it yielded less than untreated seed on peat. The chemical analyses showed that the poor performance of γ‐BHC on the peat site could not be explained by its failure to persist, because the soil still contained considerable quantities of γ‐BHC at the time of insect attack. Possible reasons may be sorption of the poison by organic matter making it less available, and deeper sowing, permitting larvae to reach the plants without prolonged contact with the insecticide.

Bayer 38156 (O‐ethyl S‐p‐tolyl ethyl phosphonodithioate) and trichloro‐nate (O‐ethyl O‐2,4,5‐trichlorophenyl ethyl phosphonothionate) persisted in soil long enough and were sufficiently toxic to wheat bulb fly to suggest that organophosphorus compounds might provide alternatives to chlorinated hydrocarbon insecticides for control of the fly.

Analyses made on seeds dressed at the laboratory for the experiment showed that the amounts of insecticide on seeds were smaller than expected and that the amounts on individual seeds differed greatly. Of ten samples of seeds dressed commercially with y‐BHC, three carried very little insecticide, and the variations in the other seven samples were greater than with experimentally applied dressings.
The toxicity of tributyltin oxide to the wood‐boring beetles Lyctus brunneus Steph. and Anobium punctatum (Deg.)
Authors: BAKER J. M. , TAYLOR JEAN M.
Published: February 2008

When tributyltin oxide (TBTO) was tested by British Standard 3653 against Lyctus brunneus, 0·5 % solution, equivalent to 0·72 g/m2 surface application, gave almost complete protection. Tests to BS 3651, using larvae of Anobium punctatum transferred into fully impregnated wood gave toxic limits of 1·39–2·93 kg/m3 TBTO when benzene was used as diluent. The use of white spirit as diluent gave lower toxic limits, probably due to combined toxic action of TBTO and white spirit residues. TBTO appears to have no contact action against the insects tested.

Probit analysis of the test with A. punctatum gave an LD 50 of 0·254 kg/m3 and an LD99 of 3 kg/m3. The advantage of treating results by probit analysis rather than by deriving ‘toxic limits’ is discussed.
Effect of wax and lanolin emulsions on the efficiency of potato‐blight fungicides in laboratory tests
Authors: MCINTOSH A. H. , EVELING D. W.
Published: February 2008

Four potato‐blight fungicides (copper oxychloride, tetrachloroisophthalo‐nitrile, zineb and fentin acetate) were formulated either by adding emulsions of paraffin wax or lanolin to solid fungicide dispersed in water, or by dissolving the fungicide in wax or lanolin and then emulsifying the solution; all emulsions were non‐creaming and extremely stable. These formulations were compared in the laboratory with commercial wettable powders of the same fungicides for their ability to protect detached potato leaflets against infection by Phytophthora infestans (Mont.) de Bary; in these and in other laboratory tests, the quality of rain‐fastness, or tenacity, was involved directly or indirectly.

Most of the wax or lanolin formulations gave better protection than the wettable powders. It is suggested that the wax and lanolin acted as viscous stickers, suitably increasing the rain‐fastness of deposits on leaflets; and that when the fungicide was dissolved in the wax or lanolin before emulsification, the particle size of the dispersed fungicide was extremely small, a quality that increases biological action.
Screening trials of materials for suppressing spore production by Gloeosporium perennans on apple trees
Authors: CORKE A. T. K.
Published: February 2008

In a screening trial of thirteen potential spore suppressants carried out in 1965, sporing cankers on Cox's Orange Pippin shoots, induced by inoculation with Gloeosporium perennans in November 1964, were treated at bud‐burst with the test materials. The most effective spore suppressant was dichlo‐fluanid; this, with the next five most effective materials and six additional materials, was used in a second trial in 1966, when the greatest reduction in spore production was obtained with tetrachloro‐o‐cresol.

A general trend towards correspondence between spore output from cankers and infection on neighbouring fruits was shown, but this could be modified by a number of factors, including changes in spore viability caused by fungicide treatment.