bluuebunny/crossref_metadata_2025 huggingface dataset:
APHID BEHAVIOUR ON HEALTHY AND ON YELLOWS‐VIRUS‐INFECTED SUGAR BEET
Authors: BAKER PETER F.
Published: February 2008

Myzus persicae Sulz., M. ascalonicus Doncaster, Aphis fabae Scop, and Aulacorthum solani Kalt., when caged on sugar‐beet leaves in the glasshouse preferred yellows‐virus‐infected leaves to healthy ones; they chose those with the most severe symptoms on which they bred more rapidly and lived longer than on green leaves. M. persicae behaved similarly on whole plants in the glasshouse. The previous host influenced the aphid's preference. Differences between the multiplication rates of aphids on healthy plants of inbred sugar‐beet varieties were eliminated or reversed by infection with yellows virus.

Spraying healthy plants with either sugar solutions or hydrolysate of casein increased the multiplication rate of M. persicae, but much less than did virus infection.
STUDIES ONGLOEOSPORIUM MUSARUMCKE. AND MASSEE CAUSING STORAGE ROTS OF JAMAICAN BANANAS
Authors: MEREDITH D. S.
Published: February 2008

Experimental inoculations indicate that several factors may influence the extent to which anthracnose, caused byGloeosporium musarum, develops on bananas following wound‐infection. Severity of disease increases with increasing ‘grade’ of maturity, ‘full’ fruit being more seriously affected than ‘thin’ fruit. The evidence suggests that Gros Michel fruit is less susceptible to this form of rot than fruit of the Lacatan or Robusta varieties. The amount ofGloeosporium‐rot on fruit imported into the United Kingdom undergoes marked seasonal variation, being greatest during autumn and winter.

The presence of perforated ‘Polythene’ bags during cold storage (55° F.) appears to favour slightly the development of disease. Bagging had no significant effect on rotting during the subsequent ripening period. After wound‐inoculation, disease incidence and severity decreased appreciably with increasing periods of storage at tropical temperatures (76–87° F.). Such a decrease was evident even when the humidity at the surface of the fruit was maintained at a high level (92–100%).

In several shipping trials, a post‐harvest fruit‐dip treatment with nystatin (200–400 p.p.m.) effected 40–70% control of anthracnose.
INVESTIGATION OF FIRE‐BLIGHT OF PEAR IN ENGLAND
Authors: CROSSE J. E. , BENNETT MARGERY , GARRETT CONSTANCE M. E.
Published: February 2008

Outbreaks of fire‐blight, caused by Erwinia amylovora, in Kentish orchards during 1957 constitute the first authenticated record of the disease in Europe. The origin of the disease is unknown, but evidence suggests that it was not present in the orchards prior to 1957.

The seasonal development and symptoms of the disease are described in detail. Fire‐blight attacked trees only during the growing season; infection began in the blossoms, particularly summer blossoms, and spread into the branches forming cankers, in many of which the pathogen remained viable during the winter 1957–8. In the orchards examined there was a higher incidence of new infections by July 1958 on trees attacked the previous year than on those which were then healthy, and this is discussed in relation to overwintering sources of inoculum. The distribution of the disease in orchards during 1957 and 1958 was consistent with spread by pollinating insects rather than rain.

The outstanding susceptibility of the variety Laxton's Superb in all localities was attributed partly to its tendency to produce abundant secondary blossom. Inoculations of blossoms, fruits, shoots and branches showed it also to have less inherent resistance than the varieties Williams's Bon Chrétien and Conference, neither of which has been seriously affected in the field. The progress of symptoms following inoculation of pear and infection experiments with apple, Cotoneaster sp., Pyracantha sp., and other hosts, are described.

A comparison of climatic conditions favouring the disease in the U.S.A., i.e. high temperatures and high humidity, with meteorological records at East Malling, suggests that epidemic infection of spring blossom would be exceptional in this country.
COMPARISON OF TWO BARLEY YELLOW‐DWARF VIRUSES IN GLASSHOUSE AND FIELD EXPERIMENTS
Authors: WATSON MARION A. , MULLIGAN T. E.
Published: February 2008

Comparisons were made of the host ranges, interactions in infected plants, and effects on yields of cereals of two isolates of barley yellow‐dwarf virus, one avirulent, RV, obtained from Rothamsted farm (Watson & Mulligan, 1956) and the other virulent, KV, obtained from Kent. They resembled each other and the American yellow‐dwarf viruses in their ability to infect wild grasses but differences were found when the infection tests were made using inbred lines of the same grass species. KV infected one variety each of rice, rye and maize, and caused symptoms in each.

When plants were first infected with RV and later, when symptoms had fully developed, with KV, they suffered the same loss of yield from KV as did plants infected for the same length of time with KV alone. Therefore plants infected with RV were not protected against infection with KV. Similarly, aphids (Rhopalosiphum padi L.), fed first on sources of RV and then on KV, transmitted mainly KV so there was no evidence of protection in the insect vectors.

Effects on yield of cereals were related to the time of appearance and intensity of symptoms. The effect of RV was not only less than that of KV but was also more variable.
THE USE OF SOIL INSECTICIDES TO CONTROL POTATO APHIDS AND VIRUS DISEASES
Authors: BURT P. E. , BROADBENT L. , HEATHCOTE G. D.
Published: February 2008

A replicated trial was done to find whether the insecticides Thimet and Rogor applied in the soil affected the spread of aphid‐transmitted viruses from infected to healthy plants with potato crops. The insecticides were applied at planting as activated carbon formulations at rates equal in cost to three sprays with DDT emulsion at 2 lb. DDT per acre. The infected plants were removed (rogued) in late June.

Thimet applied along the furrows with the fertilizer, and Rogor applied in individual doses beneath each tuber, kept the plants free from aphids from a week after the plants emerged until early August. Thimet in individual doses was less effective but greatly decreased the aphid infestation. All treatments prevented or greatly decreased the spread of leaf‐roll virus, but they only slightly decreased the spread of virus Y. No treatment damaged the plants or depressed yields significantly.

Tubers harvested from the plots treated with insecticides contained only very small quantities of the insecticides, but shoots from them, when infested with adult Myzus persicae (Sulz.), carried fewer aphids a week after infestation than did shoots from control tubers. Shoots of tubers from treated plots also grew more slowly than those from the controls.

The aphicidal efficiency of Thimet applied as individual doses separated from the tubers by distances of up to 6 in., decreased as the distance increased, but the effect of distance became less as time passed.

Reasons for the differences in the behaviour of the insecticides are discussed, and the possibilities that the method offers to control virus diseases. The application of insecticides to soil promises to be a useful way of controlling the spread of viruses, provided the harvested crop is free from toxic residues.
THE EFFECTS OF FUNGICIDE‐INSECTICIDE SEED TREATMENTS ON EMERGENCE, GROWTH AND YIELD OF IRRIGATED COTTON IN THE SUDAN GEZIRA
Authors: TARR S. A. J.
Published: February 2008

Fungicide‐insecticide seed treatment, particularly with methoxyethylmercuriacetate (MEMA) and dieldrin, often improved emergence, growth and yield of irrigated Egyptian‐type cotton (Gossypium barbadense) in the Gezira area of the Sudan. Such treatment reduced post‐emergence wilting and death of seedlings resulting from termite attack, and also reduced pre‐emergence mortality probably caused primarily by soil insects, but appeared to have little effect on the incidence of termite damage to tap‐roots of mature plants at the end of the season. Termite attack tended to be worse in close rotations, and the beneficial effects of fungicide‐insecticide seed treatment were greater in three‐course than in four‐course rotation plots. In one experiment treatment improved growth and yield of cotton plants in the apparent near‐absence of insect pests and diseases, this effect perhaps deriving from control of minor root damage caused by soil insects and/or fungi.

Certain seed treatments, notably those containing MEMA and γ‐BHC, were slightly phytotoxic, but at the levels applied—0.043% mercury/seed and 0.12—0.24% insecticide/seed—this aspect, although needing further investigation, seems unlikely to be of serious practical significance in the Sudan Gezira where high sowing rates are the rule; any slight phytotoxicity would probably be outweighed by the protective effects of the treatment. Phytotoxicity tended to become more pronounced with increasing number of seeds per sowing hole.
EXPERIMENTS ON THE HERBICIDAL ACTION OF 1,1‘‐ETHYLENE‐2,2’‐DIPYRIDYLIUM DIBROMIDE
Authors: MEES G. C.
Published: February 2008

Light was shown to increase the rate of kill obtained with 1,1′‐ethylene‐2,2′‐dipyridylium dibromide, without being essential for herbicidal action. The light effect, which was observed only in green tissues, increased with intensity up to about 10 k‐lux, and was inhibited by N‐(4‐chlorophenyl)‐N,N'‐dimethyl urea or the absence of oxygen, but not by potassium cyanide or in a carbon‐dioxide‐free atmosphere. The herbicide was also shown to stimulate and inhibit respiration. The stimulation was transitory, and appeared to depend on a continuous supply to the tissues, while the inhibition did not.

These observations are interpreted, consistently with chemical evidence, to show that the reduction of the herbicide to its free radical form is an essential step in the sequence of toxic reactions. It is supposed that energy for reduction comes from the photolysis of water in the light, and from respiration in the dark. Once formed, the radical may initiate chain reactions in the presence of oxygen which end in the degradation of essential cytoplasmic components.
METABOLISM OF PLANT GROWTH REGULATORS
Authors: LUCKWILL L. C. , LLOYD‐JONES C. P.
Published: February 2008

2,4‐Dichlorophenoxyacetic acid (2,4‐D) labelled with 14C in either the carboxyl or methylene group was fed through the transpiration stream into detached leaves of black currant, which is sensitive to this herbicide, and of red currant which is highly resistant. The leaves were then kept in darkness and the evolution of 14CO2 was followed; subsequently the leaves were extracted and the metabolic products examined by chromatography and radioassay.

The chief difference between the species is the ability of the red‐currant leaf to oxidize approximately 50% of the carboxyl and 20% of the methylene carbon from the side chain of the 2,4‐D over a period of 1 week: in the black‐currant leaf only about 2% of the 2,4‐D is broken down in this way in the same period. The red‐currant leaf can metabolize in a similar manner the side chains of 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T), 4‐chlorophenoxyacetic acid (4‐CPA) and 2‐methyl‐4‐chlorophenoxyacetic acid (MCPA), but not of 2‐chlorophenoxyacetic acid (2‐CPA).

In both species 5–10% of the 2,4‐D taken up by the leaves is converted to water‐soluble compounds which are biologically inactive in the oat mesocotyl and Coleus abscission tests and which yield 2,4‐D on hydrolysis with 2N sulphuric acid. The failure of 2‐CPA to produce growth responses in currants, and probably in other plants, is attributable to the conversion of 70–80% of the applied chemical to water‐soluble inactive compounds. A further 5–10% of the 2,4‐D entering the leaf is metabolized to a biologically active, non‐acidic neutral compound. Analogous compounds were formed in leaves treated with 2,4,5‐T or 2‐CPA.

In both species a variable proportion (10–30%) of 2,4‐D, 2,4,5‐T and 2‐CPA are bound in the leaf tissue and cannot be removed by aqueous or organic solvents or by mild hydrolysis.

The red currant is killed by low concentrations of 2,4,5‐T even though this compound is broken down in the leaf as rapidly as 2,4‐D. It is noteworthy that death is delayed and there is an absence of the epinastic reactions normally associated with damage by phenoxy‐acid herbicides.
OBSERVATIONS ON THE EFFECTS OF THE PARASITIC NEMATODES DITYLENCHUS MYCELIOPHAGUS, APHELENCHOIDES COMPOSTICOLA AND PARAPHELENCHUS MYCELIOPHTHORUS ON THE GROWTH AND CROPPING OF MUSHROOMS
Authors: GOODEY J. B.
Published: February 2008

The parasitic nematodes Ditylenchus myceliophagus, Aphelenchoides composticola and Paraphelenchus myceliophthorus severely damage mushroom mycelium and, in great numbers, reduce or even prevent cropping. The relationships between fluctuation of nematode population, state of the mycelium, duration of cropping and the yield of mushrooms are illustrated in a series of figures.
THE MANNER OF TRANSMISSION OF SOME BARLEY YELLOW‐DWARF VIRUSES BY DIFFERENT APHID SPECIES
Authors: WATSON MARION A. , MULLIGAN T.
Published: February 2008

Some barley yellow‐dwarf (BYD) viruses isolated from cereal crops in Great Britain were transmitted by Rhopalosiphum padi, L. and others were not. Sitobion fragariae (Walker), S. avenae (Fabricius), and Metopolophium dirhodum (Walker) all transmitted viruses of both types, but they usually transmitted those of which Rhopalosiphum was a vector less readily than did R. padi. The transmissibility of a virus by a given aphid species was not affected by transmission with another, less efficient, vector species. Neomyzus circumflexus (Buckt.) and Rhopalosiphum maidis (Fitch) transmitted the few viruses with which they were tested.

A few R. padi acquired virus from infected leaves during 30 min. feeding and inoculated healthy seedlings during 15 min. feeding, but the minimum total time taken to acquire and transmit was 10 hr. and 32 hr. were needed for about half the aphids that were able to acquire and transmit virus to do so. This may indicate the existence of a short latent period of the virus in the vector, although the evidence is not conclusive. The times spent on infected plants influenced the results more than those spent on healthy ones; many transmissions occurred with short feeding times on healthy plants so long as the time spent on infected leaves was long, but the reverse was not true. Nymphs of R. padi that moulted after they left infected plants on which they fed long enough to become infective, infected slightly fewer plants than adults fed for the same times.
SUGAR‐BEET YELLOWS: FURTHER STUDIES ON VIRUSES AND VIRUS STRAINS AND THEIR DISTRIBUTION IN EAST ANGLIA, 1958‐59
Authors: RUSSELL G. E.
Published: February 2008

Experiments have shown that, as in the years 1955‐57, two yellowing viruses, beet yellows virus (SBYV) and sugar‐beet mild yellowing virus (SBMYV), were present in commercial sugar‐beet crops in East Anglia in 1958 and 1959. The evidence that they are not closely related viruses has been confirmed. In both years the prevalence of the two viruses was estimated by aphid transmissions from yellowed sugar‐beet leaves to healthy sugar beet and Chenopodium capitatum seedlings in the glasshouse, and in 1959 additionally by examination of symptoms on field plants. SBMYV was more common than SBYV over the whole region in 1958, but in 1959 SBYV was slightly more prevalent than SBMYV. In both years SBYV was found more often in the southern than in the northern parts of the region. The results described in this paper suggest that breeding for tolerance to SBMYV may be at least as important economically in East Anglia as breeding for tolerance to SBYV. A wide range of SBYV strains was present in East Anglia in 1959, most of the strains being those which caused severe symptoms in sugar beet and C. capitatum.
FACTORS AFFECTING THE SPREAD OF APHID‐BORNE VIRUSES IN POTATO IN EASTERN SCOTLAND
Authors: CADMAN C. H. , CHAMBERS J.
Published: February 2008

Experiments at Invergowrie, south‐east Perthshire, showed that the extent of spread of potato leaf‐roll and Y viruses varied from year to year and that virus Y consistently spread more than leaf roll. Most spread of Virus Y occurred before the end of June and of leaf‐roll virus before the end of July. Both viruses spread slightly more in late‐ than in early‐planted crops. When plants with leaf roll and already colonized by Myzus persicae were placed in a healthy crop of Majestic potatoes at intervals during the season, the amount of virus spread decreased rapidly with increasing age of the crop. Spread of leaf roll occurred in all of twenty‐five ‘seed’ crops in different districts of eastern Scotland in 1955 but in only twenty out of thirty‐six similar crops in 1956. Annual and regional differences in virus spread appear to reflect differences in the time at which migrant aphids reach potato crops in early summer and the rate at which infestation builds up in the crops.
RED CLOVER MOTTLE VIRUS
Authors: SINHA R. C.
Published: February 2008

A virus, provisionally named red clover mottle virus (RCMV), isolated from red clover plants in England, seems distinct from any previously described. It was transmitted by mechanical inoculation of sap to many legumes and to Gomphrena globosa L., but it was not transmitted by six aphid species, or through soil or through seeds.

RCMV is inactivated in 10 min. between 60 and 63°C., and in 8 days at 18°C., but survives for long periods at ‐20; sap was not infective when diluted more than 1/1000. The virus is soluble in the pH range (4–7) in which it is stable. It was precipitated without inactivation by 50% saturated ammonium sulphate solution, but it was inactivated by ethanol or acetone. Partially purified preparations contained polygonal particles about 28 mμ in diameter. Serological tests showed no antigens in common with broad bean mottle, true broad bean mosaic or lucerne mosaic viruses.
THE ACTION OF COPPER IN ANTIFOULING PAINTS
Authors: CRISP D. J. , AUSTIN A. P.
Published: February 2008

Experiments on the number of barnacle cyprids found on plane surfaces and on the surface of small pits coated with compositions containing different amounts of cuprous oxide show that the presence of copper does not deter the cyprids from attempting to settle. Copper‐oxide paints do not inhibit settlement appreciably; their efficiency as antifouling agents is caused by the toxic action of copper on cyprids and young spat after initial attachment.

The cementing of the shell to the substratum in young barnacles which have survived metamorphosis appears to be hindered by the presence of copper paints so that they are easily dislodged.
THE INFLUENCE OF GROWTH STAGE ON THE RESPONSE OF RED CLOVER (TRIFOLIUM PRATENSE L.) TO GIBBERELLIC ACID
Authors: STODDART J. L.
Published: February 2008

The response of seedling and first harvest year plants of red clover (Trifolium pratense L.) to treatment with gibberellic acid (GA) at various growth stages is described.

Seedlings sprayed before the seventh leaf stage developed into single‐stemmed plants; treatment with GA at the third‐ or fourth‐tiller stage resulted in final stem numbers similar to those of controls. Emergence was earliest, and the number of heads per plant greatest where sprayings were delayed until the third‐ or fourth‐tiller stage.

In first harvest year plants significant increases in the number of heads per stem were obtained with certain treatments, especially those which had two applications of 0.5 mg. GA per plant during the elongation of the first four internodes. This was related in all treatment groups to modifications of the branching pattern, and also to the increased incidence of multiple heading. Earlier emergence resulted from treatment at all growth stages, the effect being maximal where three well‐spaced sprayings were applied during active stem extension.
STUDIES ON GLOEOSPORIUM MUSARUM CKE. & MASSEE CAUSING STORAGE ROTS OF JAMAICAN BANANAS
Authors: MEREDITH D. S.
Published: February 2008

Gloeosporium musarum Cke. & Massee is the most important fungus associated with finger‐stalk rot of Jamaican Lacatan bananas, Fusarium spp. being of minor importance. Sodium salicylanilide (Shirlan WS), at concentrations of 0.5, 1.0 and 1.5%, provided approximately 30, 50 and 65% control, respectively, when inoculated fruit was dipped for 1 min. in the compound: severe phytotoxic effects were caused by all concentrations. When Shirlan WS treatment was followed by rinsing in water, there were no phytotoxic effects and approximately 15, 35 and 40% control of finger‐stalk rot, respectively, was obtained. 1.0 and 1.5% Shirlan WS also effected good control of anthracnose (G. musarum), both with and without post‐treatment washing.

Moderate to poor control of Gloeosporium rot was obtained when Shirlan WS/washing treatment was delayed for more than 24 hr. after inoculation. A 2 min. immersion period in Shirlan WS was more effective than shorter periods: a momentary dip was ineffective.

The antibiotic nystatin (200 and 400 p.p.m.) had no significant effect on the incidence of finger‐stalk rot: also, the severity of main‐stalk rot was not reduced appreciably.

Practical considerations arising from the possibility of commercial‐scale treatment with Shirlan WS are discussed.
Field trials on the control of club root in Brassicae
Authors: WIGGELL P. , HAWKEN R. H. , WIGGELL D. , COCK L. J. , BANT J. H.
Published: February 2008

Experiments were made in 1957‐59 on the fungicidal control of club root in cauliflowers (summer and winter), brussels sprouts, summer cabbages and savoys. Plants were treated immediately before setting out or in their final position.

Pure (100%) calomel used in suspension at 1 and 2 oz. per pint gave best control of the disease: the 4% calomel paste method was effective but treated plants suffered an initial check from which they only slowly recovered. Formulations of pentachloro‐nitrobenzene and of aldrin did not give satisfactory control.

Several methods of applying metham‐sodium were tried but gave poor control of the disease.
Saprophytic colonization of wheat straw by Cercosporella herpotrichoides Fron and other fungi
Authors: MACER R. C. F.
Published: February 2008

In liquid cultures Cercosporella herpotrichoides utilized both organic and inorganic sources of nitrogen and showed an absolute requirement for thiamin. On nutrient agar and through sterilized straw, C. herpotrichoides grew more slowly than other facultative fungal parasites of cereal roots and stem‐bases.

The competitive saprophytic ability of C. herpotrichoides was found to be very limited. The observation that saprophytic colonization of straw tissue by Ophiobolus graminis declined as invasion progressed inwards was confirmed and found to occur also with C. herpotrichoides and Helminthosporium sativum but not with Fusarium culmorum.

It is concluded that C. herpotrichoides exhibits a low competitive saprophytic ability and is therefore unlikely to colonize straw in the soil.
The survival of Cercosporella herpotrichoides Fron in wheat straw
Authors: MACER R. C. F.
Published: February 2008

The saprophytic survival of Cercosporella herpotrichoides in naturally infected and artificially infested wheat straw has been investigated. Test pieces of straw containing the fungus were buried both in unsterilized soil in laboratory containers and in the field. Survival of the fungus was assessed by its ability to produce viable and infective spores on the surface of the recovered pieces of straw when incubated in a moist chamber. It was found that C. herpotrichoides survived, virtually undiminished in vitality, in straw buried for 3 years, the maximum period tested. Straw colonized by C. herpotrichoides was observed to decompose more slowly in the soil than did uninoculated straw; this suggests a mechanism whereby C. herpotrichoides may be enabled to survive for such long periods in the presence of competitors.
Observations on the biology of chrysanthemum eelworm Aphelenchoides ritzema‐bosi (Schwartz) Steiner in florists' chrysanthemum
Authors: HESLING J. J. , WALLACE H. R.
Published: February 2008

The chrysanthemum eelworm moved in sand and in a clay soil at much the same rate as other eelworm species so far studied. Leaf washing and soil examination in infested chrysanthemum plots showed that the eelworm never spread laterally through the soil or from leaf to leaf more than to the second row of plants from the source of infestation, a maximum distance of about 30 in. At Rothamsted and in the National Chrysanthemum Society's variety trial the number of infested varieties increased greatly in September, during periods of heavy mists. Experiments with isolated leaves, artificially infested and kept under either dry or humid conditions suggested that eelworms were more active in humid conditions. They invaded isolated leaves within 15–30 min. In pot experiments, eelworms added to soil invaded chrysanthemum plants inducing symptoms in 18 days: 26 days after such inoculations no eelworms could be detected in the soil. Few eelworms persisted in fallow soil in pots after 32 days. No eelworms were found after the end of November in soil taken from an infested field plot at intervals between August 1959 to January 1960. Attempts to infest plants with eelworms from stored soil taken from highly infested plots failed. Examination of stools during the winter showed that many eelworms were present in the green tissues. It is concluded that infestation from eelworms which persist over the winter in soil is slight and that the main source of the pest is the chrysanthemum stool.
Observations on the biology of chrysanthemum eelworm Aphelenchoides ritzema‐bosi (Schwartz) Steiner in florists' chrysanthemum
Authors: HESLING J. J. , WALLACE H. R.
Published: February 2008

In stained sections of eelworm‐infested chrysanthemum leaves the earliest effect of the attack is the appearance of a brown substance inside the leaf cells; this browning extends and ultimately reaches the leaf epidermis. The number of chloroplasts dwindles, the cell walls break down and large spaces appear in the leaf. Finally the leaf shrinks, the epidermis disintegrates and the brown substance is found on all the cell walls. The collenchyma around the main veins, where it reaches the upper and lower epidermis, does not break down until the final stage of attack.

Cuttings of thirteen chrysanthemum varieties, each artificially infested with about 110 eelworms, showed leaf blotches, stunting, blindness, browning of the stem and leaf petiole, leaf distortion, leaf scars or feeding areas and puffy, blistered and puckered leaves. Infested cuttings with severe symptoms may produce side‐shoots or breaks which seem healthy but become badly infested later in the season when the plants are wetted by rain or prolonged mists. The eelworms often failed to penetrate further than the substomatal space in the youngest leaves. All the symptoms listed above, except leaf blotches, probably result from ectoparasitic feeding by the eelworm.
The epidemiology of apple scab (Venturia inaequalis (Cke.) Wint.)
Authors: HIRST J. M. , STEDMAN O. J.
Published: February 2008

The number of ascospores caught by automatic volumetric spore traps differed widely in six orchards where the air was sampled in some or all of the years 1955 to 1959. To compare amounts of inoculum in different orchards the total catch in each was expressed as the ‘relative ascospore dose’. The reason for the much smaller doses in the later years is uncertain. The results confirmed earlier work on the phenology of ascospore liberation and stressed the practical need to decrease their number as much as possible.

Because conidia have previously been trapped almost only on wet and windy days, they have been considered to be rarely air‐dispersed. Our apparatus, which efficiently traps dry conidia but catches water‐borne ones only when in very small droplets, caught airborne conidia in all orchards when they operated during summer. Traps among heavily infected, unsprayed trees caught most conidia around noon on warm dry days and the highest concentration measured exceeded 1300 per m.3of air.
The influence of sunshine and rain on tea blister blight, Exobasidium vexans Massee, in Ceylon
Authors: VISSER T. , SHANMUGANATHAN N. , SABANAYAGAM J. V.
Published: February 2008

The germination of spores of blister blight of tea (Exobasidium vexans Massee) requires moisture, but 0.1 in. of rain in a day provides sufficient for a high percentage of germination to occur; more rain does not materially increase germination. Spores are killed by sunshine of a few hours' duration, even if there is adequate rain on the same day. An average of about 3 3/4 hr. of sunshine per day over 5 days is enough to reduce the blister‐blight disease to subeconomic levels. Ten‐day spraying rounds with copper fungicide usually give adequate control of the disease but add to the cost of production. A method is put forward of using recorded sunshine hours as the criterion in deciding on the frequency of spraying; spraying is postponed, by successive 5‐day periods, until the average sunshine for the previous 5 days has dropped below 3 3/4 hr. A reduction approaching one‐half of the number of spray applications can be made in this way.
Infection of bean plants (Vicia faba L.) with Botrytis cinerea and B. fabae
Authors: DEVERALL B. J. , WOOD R. K. S.
Published: February 2008

The infection of bean plants (Vicia faba L.) by Botrytis fabae has been studied by inoculating detached leaves with standard volumes of spore suspensions of known concentrations, or with single spores.

Increasing the number of spores in the inoculation drops increased the number of lesions, and lesions were more readily produced on older than on younger leaves.

The addition of glucose, a number of other carbohydrates, and also sodium polypectate and pectin, increased the number and rate of the spread of lesions. Xylose caused a decrease, and a number of nitrogen compounds had little effect.

The number and rate of spread of lesions was increased if the surface of leaves were gently rubbed with a mild abrasive before inoculation. Calcium‐deficient plants were more susceptible than plants which had received normal nutrition. Deficiencies of other major elements had much less effect.

A larger proportion of the spores in inoculation drops germinated when these drops were on older leaves, when the drops contained glucose, and on leaf surfaces that had been gently abraded. Addition of xylose reduced the amount of germination and the fungus grew very poorly in liquid culture when this was the only carbon source. The addition of small quantities of glucose allowed the fungus to use xylose as efficiently as glucose.

When single spores were used to inoculate leaves, very different results were obtained with leaves taken from different plants, but under some conditions single spores often induced lesion formation.

B. fabae caused lesions more readily than did B. cinerea, in spite of the fact that a greater proportion of B. cinerea spores in inoculation drops germinated.
Further observations on the reaction of wheat varieties to physiologic races of loose smut
Authors: MANTLE P. G.
Published: February 2008

The reaction of forty‐one wheat varieties to the three Cambridge physiologic races of Ustilago tritici has been determined by a combination of the embryo test and growth in the field. Wide variations in susceptibility were observed and there was no consistent relationship between the extent of mycelial distribution in the scutellum and subsequent field reaction to infection. Immunity is rare. The best differential varieties for identifying the three races are suggested.
Observations on the use of predacious fungi for the control of Heterodera spp
Authors: HAMS A. F. , WILKIN G. D.
Published: February 2008

Laboratory and pot experiments by various workers up to 1956 suggested that the effects of eelworm attack on certain crops could be partly overcome by inoculating eelworm‐infested soil with the mycelium of predacious fungi.

The present paper demonstrates some of the factors operative in soil which affect the ‘predacity’ of some of these fungi.

The results obtained strongly suggest that under laboratory conditions and in pot cultures congenial conditions for growth in soil of the predacious fungi can be produced but that, in the field, only sparse growth of these fungi can be obtained, insufficient to affect eelworm attacks.

The use of farmyard or green manure has consistently given better crops in eelworm‐infested soils irrespective of whether predacious fungi were naturally present 01 added.
Cherry leaf‐roll virus
Authors: CROPLEY R.
Published: February 2008

A virus was transmitted consistently by sap inoculation from cherry trees with leaf‐roll disease to herbaceous indicator plants, from tobacco to Prunus avium and from P. avium to P. pennsylvanica.

Herbaceous host reactions, physical properties and particle size and shape of the virus were similar to those of arabis mosaic, raspberry ringspot and tomato black‐ring viruses. Plant protection and gel‐diffusion serological tests indicated that cherry leaf‐roll virus is distinct from arabis mosaic, raspberry ringspot, tomato black‐ring, tobacco ringspot and tomato ringspot viruses.
Viruses causing rasp‐leaf and similar diseases of sweet cherry
Authors: CROPLEY R.
Published: February 2008

Trees with rasp‐leaf symptoms have been found in seventeen orchards in England. In some orchards only a few trees are infected, while in others the disease is prevalent.

Transmission tests from diseased trees indicate that raspberry ringspot virus is the cause of cherry rasp‐leaf disease in most English orchards, but arabis mosaic virus can cause similar symptoms.
The toxicity of mixtures of zinc and copper sulphates to rainbow trout (Salmo gairdnerii Richardson)
Authors: LLOYD R.
Published: February 2008

The toxicity to rainbow trout of a mixture of zinc and copper sulphates in relatively low concentrations can be calculated from the toxicities of the individual metals by assuming that they exert a similar joint action. Higher concentrations of the mixture in soft water exhibit a synergistic action.
Changes in the free amino acids and amides in tomato plants inoculated with tomato spotted wilt virus
Authors: SELMAN I. W. , BRIERLEY M. R. , PEGG G. F. , HILL T. A.
Published: February 2008

Leaves of tomato plants grown in water culture in growth rooms were inoculated with sap from healthy tomato leaves or with sap containing tomato spotted wilt virus (t.s.w.v.). Changes in the free amino acids and amides of stems and of inoculated leaves, stem growth and infectivity were determined. Samples were analysed 5, 9, 13 and 17 days after inoculation using two‐dimensional paper chromatography.

Inoculation with sap from healthy leaves, mixed with celite and sodium sulphite, caused small increases in glutamic acid, asparagine, glycine and serine in the inoculated leaves, and in glutamic and aspartic acids in the stems.

In leaves inoculated with t.s.w.v., glutamine and asparagine increased greatly, reaching maxima at day 13. Both infectivity and amide levels were greater with more concentrated inoculum. The total free amino acids increased in leaves inoculated with t.s.w.v. by 150–180%. Increases were found in α‐alanine (day 9, 13 and 17) and in aspartic acid, valine, glycine and the leucines (day 13).

Systemic infection of stems increased total free amino acids by 200–300% and amides by more than 400%. Serine, threonine, phenyl‐alanine, proline and the leucines increased at day 9 and reached maxima at day 13. Glutamine, asparagine, glutamic acid, aspartic acid, valine, tyrosine, α‐alanine, glycine and γ‐amino‐butyric acid increased at days 13 and 17.

Changes in total free amino acids in stems and leaves were closely correlated with changes in infectivity.

Five days after inoculation and 3 days before symptoms appeared, the levels of serine and threonine in the stems of plants receiving a dilute inoculum were less than those in controls.

It is suggested that accumulation of NH2 compounds in an infected plant may interfere with virus synthesis; this may explain the observed cyclical changes in infectivity.

Free tyrosine and hydroxylysine were recorded for the first time in leaves and stems of healthy tomato plants and tyrosine and methionine in healthy roots.
Laboratory and field studies on the relation of arabis mosaic virus to its nematode vector Xiphinema diversicaudatum (Micoletzky)
Authors: HARRISON B. D. , WINSLOW R. D.
Published: February 2008

Xiphinema diversicaudatum is widely distributed in southern Britain, mainly in heavy soils, but also in the peat soil of the Fens and in medium textured soils in the south‐west. Patches of plants infected with arabis mosaic virus (AMV) in a range of crops including some, like celery and marrow, not before known to be hosts, coincide with patches of soil infested with X. diversicaudatum. Roots of some plants infested with the nematode carried small galls; not all such plants were infected with, or even susceptible to, AMV. Adult X. diversicaudatum transmitted AMV more readily than larvae, but none of 103 nematodes, transferred when moulting, infected healthy plants. X. diversicaudatum were still infective after 24 days in moist peat, free from plants.

X. diversicaudatum is common in several districts in soil from old hedgerows but not in the adjacent fields. Hedgerow trees seem to be hosts of the nematode and at least one, elder, is also a host of AMV. In other districts, plants with AMV occur in crops near to infested hedges or isolated trees, and on land taken into cultivation after being derelict. In the Tamar Valley, Devon, X. diversicaudatum is common in pastures; white clover in these often contains AMV. Planting such fields with strawberry leads to disease outbreaks.

A few X. diversicaudatum occur down to 3 ft. in soil, but most are at 3–9 in. At a site where arable land has reverted to woodland, the nematodes apparently have spread from a hedge into the woodland at an average rate of 1 ft. per year over a period of 75 years. It is suggested that both X. diversicaudatum and AMV are common constituents of natural woodland in Britain and that their incidence has decreased since the advent of agriculture.
The development of filter‐passing organisms in Corynebacterium fascians cultures
Authors: LACEY MARGARET S.
Published: February 2008

Viable filter‐passing particles have been obtained from gall‐tissue cultures of Corynebacterium fascians. On gelatine media filtrates of the cultures first produced a faint clouding of the liquefied gelatine; this was due to masses of granules of very variable size. In some cultures further development took place, the next phase being the appearance of diplococci. Sometimes the coccal stage persisted but occasionally complete regeneration of the normal C. fascians type rod finally ensued. This sequence of growth follows the pattern designated as the ‘L phase’, occurring in the life‐history of certain bacteria. Growth of L forms probably occurs in Agrobacterium tumefaciens also.
Dispersion and deposition of airborne Lycopodium and Ganoderma spores
Authors: GREGORY P. H. , LONGHURST T. J. , SREERAMULU T.
Published: February 2008

Spores were liberated at 0.25 and 1.0m. above grass. Airborne concentrations at twenty or more points in the spore cloud were measured with specially designed and calibrated miniature suction traps, operated off a portable vacuum system. Deposition in the downwind direction was measured on artificial surfaces on the ground. Measurements were made up to 10 m. from the source.

The observed increase in horizontal cross‐wind standard deviation of the Lycopodium cloud agreed well with O. G. Sutton's theory, but was incompatible with that of W. Schmidt.

The coefficient of deposition, p, calculated from mean cloud concentration per c.c. and deposition to ground per cm.2, as well as the velocity of deposition, vg, varied with distance from source. Both p and vg were larger for Lycopodium than for Ganoderma, and at the greater distances tested, vg approximated to the expected terminal velocities of the particles in still air.

The total number (Q0) of Lycopodium spores liberated in each experiment was known, and tentative estimates of the proportion deposited within the sampling area indicated that, under day‐time winter conditions in England, the cloud lost not less than 13 to 24% of its load within 10 m. of the source.
Black‐pod disease of cocoa
Authors: SPENCE J. A.
Published: February 2008

Isolates of Phytophthora palmivora from various countries were compared for compatibility in oospore production with standard isolates of the ‘rubber’ and ‘cocoa’ groups. It was found that most of the isolates belonged to the ‘cocoa’ group, one to the ‘rubber’ group, and three did not form oospores under any circumstances.

The isolates showed different growth rates in wound‐inoculated pod tissue. Individual isolates showed different growth rates on pods of two varieties of cocoa.
Black‐pod disease of cocoa
Authors: SPENCE J. A.
Published: February 2008

Active pectolytic enzyme could not be recovered from cocoa‐pod shell tissue parasitized by Phytophthora palmivora, but was recovered from autoclaved potato blocks invaded by this parasite. Browned extracts of cocoa bean and pod tissue inactivated pectolytic enzymes of P. palmivora obtained from invaded potato blocks. When allowed to brown before exposure to enzyme, discs of cocoa‐pod tissue showed increased resistance to maceration by pectolytic enzymes of P. palmivora.

Attack of cocoa pods by a weakly virulent isolate was promoted by low oxygen tension and low temperature. Attack by a virulent strain was accelerated at low oxygen tension and retarded at high oxygen tension.

The results suggest that a balance exists during parasitism of cocoa pods by P. palmivora between the pectolytic enzyme system of the fungus and the polyphenol oxidase system of the host and that the activity of the polyphenol oxidase system acts as a host resistance mechanism.
Studies on the chemical control of Phytophthora palmivora (Butl.) Butl. on Theobroma cacao L. in Nigeria
Authors: Hislop E.C. , Park P.O.
Published: February 2008

The tenacity of a number of fungicide formulations when sprayed on to cocoa pods has been tested by applying artificial rain produced in an experimental rain tower. A general relationship between leaching of deposits and rainfall has been obtained. The effect of incomplete drying on the tenacity has been correlated with observations in the field. The effect of pod growth on the attenuation of fungicide deposits was demonstrated and possible improvements to formulations and spraying techniques are discussed.
A study of the heating of stored grain caused by insects
Authors: HOWE R.W.
Published: February 2008

The rates of increase of temperature and of population density are calculated for an insulated culture of granary weevils, assuming a Malthusian rate of increase, and basing heat production on respiration rates. This is done first by a step method, but it is shown that the increase in population density can be related to rise in temperature, irrespective of the original density, which makes a short‐cut method possible.

The calculations are then modified for the situation in which the culture is embedded in and loses heat by conduction to a bulk of uninfested grain. The spread of heat by conduction is slow; spread by convection is not considered. At I m. from a hot pocket with a steady heat output, the rise of temperature at equilibrium will be less than half the rise at the margin of the hot pocket and only 15% of this rise will be achieved in 4 weeks. The numbers of insects needed to raise the temperature of an infested pocket in a grain bulk are much larger than those required for an insulated culture. The extra time required to reach a temperature is that needed to build up a sufficient population in the original environmental conditions.

It is argued that hot pockets increase in size because of the movement of insects induced by high temperatures and by overcrowding, rather than because of spread of heat by conduction. Convection currents cause upward, but not lateral, extension of hot pockets. If sufficient insects are to develop to produce enough heat to cause high temperatures the expansion of a hot spot is necessary, so that small cages of insects cannot be used to induce heating experimentally.

Warehouse observations are described to support these predictions. Heating of home‐produced grain in Britain is caused chiefly through storing either grain which is damp and therefore heats, or dried grain which has been insufficiently cooled. Either produces an ideal environment for any stored‐grain insect species.

Stored grain should be inspected both to find insects and to measure its temperature and moisture content. Any warehouse containing grain at temperatures above 22° C. and insects should be examined monthly.
A virus causing axillary bud sprouting of tobacco in Rhodesia and Nyasaland*
Authors: GATES L.F.
Published: February 2008

A virus first found in tobacco in Rhodesia in 1958 was widespread in 1959, usually together with other viruses. It is readily transmitted by mechanical inoculation. Myzus persicae transmitted it from plants that were also infected with another virus, probably tobacco vein‐distorting virus, but not from plants infected with it alone. The aphids became increasingly likely to transmit as their feeding time on infected plants increased up to 24 hr.; after virus‐acquisition feeding times of 24–48 hr. they remained infectious for several days. The virus, named tobacco bushy‐top because of the characteristic way it stimulates the growth of axillary shoots, resembles tobacco mottle virus in many respects, and as tobacco mottle virus partially protects plants against bushy‐top virus they may be related strains.
Studies on strawberry mildew, caused by Sphaerotheca macularis (Wallr. ex Fries) Jaczewski*
Authors: PERIES O. S.
Published: February 2008

Cross‐inoculation trials have shown that Sphaerotheca macularis on strawberries is a specialized form of this fungus.

Conidia germinated consistently well on dry healthy leaf surfaces. Cardinal temperatures for germination of conidia were 2°, 20° and 35° C., while infection and sporulation were not recorded below 5° and 13° C, respectively. Conidia retained their viability for periods up to 5 weeks at 0° C. in a saturated atmosphere, and for short periods under more exacting environmental conditions. Low humidities, although injurious to conidia, especially at high temperatures, had no effect on growth and sporulation of the fungus. Light too had no effect on conidial germination and development of the fungus. Free water had a lethal effect on conidia and no germination was recorded on wet leaf surfaces.

A diurnal periodicity of spore liberation, with a maximum in the afternoon, has been observed. Rain has a drastic effect on spore dispersal, reducing the numbers trapped to very low levels. There was a steep falling gradient in the number of spores trapped both with increasing distance and height from the source.

Heavy shade, high humidities and temperatures between 60 and 80° F. were conducive to the production of perithecia. There was no evidence to show that strawberry mildew is heterothallic. Inoculation experiments have shown that the perithecia do not play any essential part in the life history of the fungus.