bluuebunny/crossref_metadata_2025 huggingface dataset:
WIREWORM POPULATIONS IN RELATION TO CROP PRODUCTION: II. POPULATION CHANGES IN GRASSLAND
Authors: ROSS D. M. , STAPLEY J. H. , COCKBILL G. F.
Published: February 2008

Six grass fields were sampled once a fortnight from July 1943 to September 1944, and the wireworms in the samples counted by the washing and flotation method.

The counts from twenty standard samples showed huge fluctuations which rendered them practically valueless as estimates of wireworm populations when treated singly. When treated as running means of four consecutive samplings, the counts showed certain seasonal trends, with minimum populations in July and August, rising populations throughout the autumn, maximum populations in the months from January to April and a sharp decline to the minimum populations again from April to July. On the average, the counts taken in winter were twice as high as those taken in the summer months.

The fluctuation was evident in all size groups based on larval length but was most marked in the wireworms ‘under 4 mm.’, ‘4 mm.’ and ‘5 mm.’

Samples taken to depths of 12 and 24 in. showed that on the average about 75 % of the wireworms were found in the 0–6 in. layer and about 90% in the 0–12 in. layer. These proportions varied considerably with the seasons.

The seasonal changes in wireworm populations observed do not correspond with those expected from the life history of Agriotes spp. Possible explanations for this anomaly are discussed, but it cannot be attributed to any known technical or biological factor. Several possibilities remain to be explored.
THE EFFECT OF PLANT EXTRACTS ON THE GERMINATION OF THE CONIDIA OF VENTURIA INAEQUALIS
Authors: GILLIVER K.
Published: February 2008

Of 1915 flowering plants 23 % gave extracts which completely inhibited the germination of the conidia of Venturia inaequalis under the experimental conditions used. The plants which gave active extracts are distributed throughout the Angiosperms, and there is no correlation with systematic position. The inhibitors were distributed generally in some plants and were localized in others, e.g. to the leaves.

Some extracts appeared merely to inhibit the germination of the conidia while others killed them.

Some inhibitors disappeared when the plants were dried, other dry material was still active when retested several months later.

Hedera Helix contains an inhibitor which is active when the extract is diluted 128 times.
THE FORMATION OF INSECTICIDAL FILMS ON BUILDING MATERIALS: II. TESTS OF THE EFFICIENCY OF VARIOUS TYPES OF PRETREATMENT
Authors: HEWLETT P. S. , PARKIN E. A.
Published: February 2008

Thirty different pretreatments have been tested, in addition to those mentioned in a previous contribution, for their efficiency in prolonging the effective toxic life of a film of pyrethrins in Shell Oil P 31 deposited on brick. Reasons for the success or failure of the various types of pretreatment are considered. Seven substances selected for further trial were tested on four more building materials—limewashed brick, wood, cement, and cement‐sand mixture. The five pretreatments which gave good results on all or most of these substrates were then tested to determine how long they would continue to support a toxic film on cement. Solutions of size and gelatin caused the greatest persistence of toxicity of the pyrethrum films. The flour beetle, Tribolium castaneum Herbst, was used throughout as the test insect.
THE INFLUENCE OF LIGHT INTENSITY ON THE SUSCEPTIBILITY OF PLANTS TO CERTAIN VIRUSES
Authors: BAWDEN F. C. , ROBERTS F. M.
Published: February 2008

Reducing the light intensity under which plants were grown in summer to one‐third increased their susceptibility to infection with tobacco necrosis, tomato bushy stunt, tobacco mosaic and tomato aucuba mosaic viruses. With the first two viruses shading increased the average number of local lesions per leaf by more than ten times and by more than five times with the second two.

Reducing the light intensity increased the virus content of sap from leaves inoculated with Rothamsted tobacco necrosis virus by as much as twenty times. As it also reduced the total solid content of sap by about one‐half, purification was greatly facilitated; crystalline preparations of the virus were readily made from shaded plants but not from unshaded controls.

Reducing the light intensity also increased the virus content of systemically infected leaves; the greatest effect was with tomato bushy stunt virus with which increases of up to ten times were obtained, but with tobacco mosaic and aucuba mosaic viruses there were also significant increases.

The importance of controlled illumination in raising plants for virus work and the possible mechanisms responsible for the variations in susceptibility are discussed.
STUDIES ON THE RELATIONSHIPS BETWEEN EARTHWORMS AND SOIL FERTILITY: I. BIOLOGICAL STUDIES IN THE FIELD
Authors: EVANS A. C. , GUILD W. J. McL.
Published: February 2008

Changes in the seasonal activity of several species of earthworms have been followed in a permanent pasture field for 18 months, 1945–6. The two soil conditions which chiefly determine activity are temperature and moisture. Other factors are the occurrence of an obligatory diapause in the two species Allolobophora nocturna and A. longa, and changes in population in A. chlorotica and Lumbricus terrestris.

Soil temperature and soil moisture also determined the weight of soil thrown up in the form of wormcasts during autumn, winter and spring. It is suggested that only two species, A. nocturna and A. longa, are responsible for wormcasts and that the other four common species present play little or no part in this activity.

At Rothamsted it was found that the previous agricultural history of the field is an important factor in determining the fauna. Old permanent pasture is characterized by a high percentage of A. nocturna and a rather lower percentage of A. caliginosa. Ploughing old permanent pasture and reseeding to grass after 1 or 2 years arable reduces the proportions of A. nocturna and A. caliginosa and increases that of Eisenia rosea. Arable fields have A. chlorotica as the dominant species and pasture fields 2–7 years grass after many years of arable fanning still show a high percentage of A. chlorotica and a low proportion of A. nocturna.

A survey of the Carse of Stirling, Scotland, showed that soil type is also an important factor in determining the earthworm fauna. A. caliginosa was the dominant species on the three soil types studied, but the subdominant species varied. On clay soil, A. longa was subdominant; on loam, A. longa and L. rubellus; on sandy soil, A. longa, L. rubellus and A. chlorotica. The dominant species of pasture land at Rothamsted, A. nocturna, was not found at Stirling.
THE PRACTICAL CONTROL OF WIREWORM BY γ‐BENZENE HEXACHLORIDE (‘GAMMEXANE’): COMPARISONS WITH DICHLORODIPHENYLTRICHLORETHANE (D.D.T.)
Authors: JAMESON H. R. , THOMAS F. J. D. , WOODWARD R. C.
Published: February 2008

Benzene hexachloride containing 13% of the insecticidally active gamma isomer known as ‘Gammexane’ has been used successfully in a considerable number of field trials in the control of wireworm. On heavily infested land the effective dosage rates associated with an appreciable reduction in wireworm population, and giving a marked improvement in plant establishment and substantial increases in yield, range between 1 and 6 lb./acre (2–12 oz./acre of Gammexane), on oats and wheat. The effective dosage rates vary and depend upon whether the insecticide is combine‐drilled, broadcast, or applied as a seed dressing.

Although D.D.T. applied by similar methods was associated with similar reductions in wireworm population, the use of this insecticide resulted in smaller yield increases.
A DIRECT‐SPRAY TECHNIQUE FOR THE BIOLOGICAL EVALUATION OF PYRETHRUM‐IN‐OIL INSECTICIDES FOR USE AGAINST STORED PRODUCT INSECTS IN WAREHOUSES
Authors: HEWLETT P. S.
Published: February 2008

A direct‐spray technique for the biological assay of pyrethrins in Shell oil P31 is described, together with the experiments leading to its adoption. The technique is such that film effects are reduced to the minimum practicable, but it is otherwise as similar as possible to the film technique described by Parkin & Green (1943). Methods for statistical analysis of the results are discussed. For the biological assay of pyrethrins in Shell oil P31, the direct‐spray method is slightly superior to Parkin & Green's film method, but both techniques should have their uses in general experimental work.
VIRUS DISEASES OF CACAO IN WEST AFRICA: I. CACAO VIRUSES 1A, 1B, 1C AND 1D
Authors: POSNETTE A. F.
Published: February 2008

As an introduction to this series of papers, a brief history is given of swollen‐shoot disease of cacao in the Gold Coast, and the nomenclature for cacao viruses is discussed.

The symptoms of four virus diseases of cacao are described in detail, together with experimental data under the headings: cross‐immunity reactions, latent period, seed transmission, staining reaction, heat inactivation and rate of spread.
VIRUS DISEASES OF CACAO IN WEST AFRICAL: II. CROSS‐IMMUNITY EXPERIMENTS WITH VIRUSES 1A, 1B AND 1C
Authors: CROWDY S. H. , POSNETTE A. F.
Published: February 2008

Experiments on cross‐immunity reactions between three viruses attacking Theobroma cacao L. on the Gold Coast are described. A field trial involving 3 acres of graft‐inoculated trees revealed some degree of protection afforded by Theobroma virus 1B against infection with virus 1A. The protection appeared to be more effective against insect inoculation than against graft transmission, being only temporary in the latter. Virus 1C (probably unrelated but not to be called Theobroma virus 2 until more evidence is available) conferred no protection against virus 1A.

The latent periods for these viruses were calculated from this experiment, which also provided data on their effects on yield. Virus 1A reduced yield by 50% in the first year after inoculation and killed the trees in the second. Virus 1B had no appreciable effect on yield; virus 1C reduced yield by 50 % in the third year after inoculation but there was no further decline in the fourth.

The rates of spread of these viruses were compared and significant differences demonstrated.
STUDIES IN THE PHYSIOLOGY OF THE ONION PLANT
Authors: HEATH O. V. S. , HOLDSWORTH M. , TINCKER M. A. H. , BROWN F. C.
Published: February 2008

A wide range of factorial experiments at Wisley on onions grown from sets included combinations of the factors: storage of sets at high and low temperatures during the winter, variety, set size, set planting date and nitrogen manuring. Bolting, yield and ripening data are recorded. One experiment was repeated in Scotland and Northumberland where early ripening was expected to be more important than at Wisley. In general, all the factors enumerated except nitrogen manuring had large effects on bolting and yield, and storage temperature had a large effect on the time of ripening. Varieties can be selected such that large sets may be used without appreciable loss by bolting and maximum yield thus secured. Storage temperatures of from 20 to 24° C., applied for about 14 weeks from October onwards, can be used to control bolting and to increase the yield even of non‐bolting strains by delaying ripening and so extending the growth period. Storage at 24° C. is more effective in preventing bolting than the lower temperatures, but 20° C. is probably more effective in delaying ripening. High‐temperature storage is probably unsuitable for sets to be planted in the north and west of Great Britain because of the difficulty of ripening the bulbs. For these districts low‐bolting strains are therefore essential. Storage at o° C. gives only a partial control of bolting and has no effect on ripening. Late planting of sets, although very effective in controlling bolting, results in a substantial loss of yield and, therefore, is not a practical measure. Nitrogen manuring had practically no effect on yield and could not be used to prevent the loss of yield caused by late planting.
THE DEVELOPMENT OF INTERNAL BOLL DISEASE OF COTTON IN RELATION TO TIME OF INFECTION
Authors: PEARSON E. O.
Published: February 2008

Inoculations of Nematospora spp. into cotton bolls at successive weekly intervals from flowering to maturity show that the symptoms produced are closely dependent upon the stage of development reached by the boll when infected. Details are given of the nature and degree of the staining and of the effects upon weights of seed and lint finally produced. During the first 4 weeks of life bolls are in the stage of rapid growth and differentiation, and infection is followed by severe disorganization of all boll structures and complete commercial loss. Bolls infected later in life develop typical stained lint, but without general breakdown of other tissues, and the degree of staining diminishes steadily with the age when infected, until, towards maturity, little or no effect is produced.

Subsidiary experiments show that inoculations of sterile water can cause death of the seed embryos, presumably by plasmolysis, in bolls up to 3 weeks of age. The effects upon the seed and consequently upon the lint following death of the embryo caused by such treatment are shown to be similar to those following feeding by uninfected insects of the genus Dysdercus, which are the normal vectors of internal boll disease.

Staining of the lint by Nematospora is due to the post‐mortem discoloration of the protoplasm of the lint hair, and its extent consequently varies inversely with the degree of vacuolation, which increases with maturity. The mode of action of the fungus and the evidence suggesting that a toxin is involved are discussed.

The bearing of the age‐damage relationship on the losses due to internal boll disease in African cotton‐growing countries is considered, and the advantages of promoting a steep flowering curve are emphasized.
THE ECOLOGY OF THE BRITISH SPECIES OF PSYCHODA (DIPTERA: PSYCHODIDAE)
Authors: SATCHELL G. H.
Published: February 2008

A study of the dispersal of the sewage‐filter Psychodids requires a knowledge of the breeding haunts and seasonal incidences of the local species of the genus. Field dung, decaying vegetable matter and organic mud form the breeding places to one of which some species confine themselves, whilst others, e.g. Psychoda seuerini Tonn., breed in a variety of materials. P. alternata Say is more restricted in its choice of breeding grounds and proved the best indicator of dispersal from sewage filters. With this fly, invasion of farms and woodland was apparent at a distance of 1/4 and 1 mile respectively from the filters, but not at a distance of 1 1/2 miles in the direction of the prevailing wind.
The Fungistatic Activity of Ethylenic and Acetylenic Compounds
Authors: McGowan J. C. , Brian P. W. , Hemming H. G.
Published: February 2008

Over eighty compounds have been assayed for fungistatic activity. Fusarium graminearum, Penicillium digitatum and Botrytis allii were used as test organisms. The preliminary results suggest that fungistatic activity is associated with the tendency of the substituents to withdraw electrons from the double bond. Nitroethylenes and fumarates are, for example, fungistatic. Tetraiodoethylene has high activity but this can hardly be attributed solely to the withdrawal of electrons from the double bond by the iodine atoms.
The Relation Between the Size of Plant and the Spread of Systemic Diseases
Authors: van der Plank J. E.
Published: February 2008

It is an implication of systemic infection by the aphis‐borne viruses that potato plants with large haulms should be specially vulnerable to infection, and this implication is supported by evidence in the field.

Haulms are reduced in size by short days, low temperatures, under‐nutrition and varietal differences. Certain observations are adduced to show that these factors reduce vulnerability. It is suggested that the transference of the potato from the short days, infertile soils and primitive cultivation on the Andes to the long summer days and productive farming of Europe and North America enhanced its vulnerability to aphis‐borne virus diseases: the further effects of changes of temperature and manurial practices in the last century need elucidation.
Virus Diseases of Cacao in West Africa
Authors: Posnette A. F. , Strickland A. H.
Published: February 2008

Experiments on the technique of insect transmission of the cacao virus 1A (swollen‐shoot) are described. This virus is unique in being transmitted by mealybugs (Coccoidea) and the experiments show that all stages of Pseudococcus njalensis Laing and of Ferrisia virgata Ckll. are vectors. These insects become infective after feeding for less than 4 hr. on the infected plant and transmit after less than 3 hr. on the test plant. The virus is non‐persistent in the vector after 3 hr. test‐feeding. The vectors can collect virus from either leaf, green shoot, bark or pod; the young symptom‐bearing leaf is the best site for infection‐feeding and the cotyledon of the bean for test‐feeding.
The Effects of D.D.T. and of Benzene Hexachloride on Bees
Authors: Way M. J. , Synge A. D.
Published: February 2008

Laboratory and field experiments were carried out during 1946 to determine the effects of D.D.T. and of benzene hexachloride (B.H.C.)* on honey‐bees and on several wild be species.

Laboratory experiments show that B.H.C. is a powerful contact and stomach poison and results of field experiments with commercial preparations confirm its danger to the foraging bee population. A few minutes' contact with treated surfaces is sufficient to cause death and blossom may remain poisonous for at least 3 days after treatment.

In the laboratory D.D.T. has a contact action at fairly high concentrations and as a stomach poison is rather more toxic than lead arsenate. In the field, commercial preparations on open blossom are apparently harmless to foraging bees.
The Toxic Action of Molybdenum in Relation to Soils and Crops
Authors: Brenchley Winifred E.
Published: February 2008

The harmful effect of molybdenum on animals is well established, but there is comparatively little knowledge of the conditions in which molybdenum is poisonous to plants. Obvious differences in response to molybdenum poisoning in different soils have been previously noted, but no adequate explanation has been put forward.

Tomatoes grown in ordinary loam showed little outward sign of poisoning with heavy doses of sodium molybdate, but some depression of crop occasionally occurred, especially when the dose was divided into early and late treatments. The response varied with season and variety. On certain light and fen soils the plants were killed at an early stage with the heavier dressing of molybdate, and seriously injured with the lighter dose, the leaves showing the golden colour characteristic of molybdenum poisoning in various plants.

The reaction of different crops varied considerably in the same soil with similar treatments. On old cucumber soil tomatoes showed no sign of toxicity even with the heavy dressing, flax was progressively damaged with increasing doses, while Solanum nodiflorum was most seriously affected even with the lighter dressing of molybdate. It was impossible to predict the reaction between soil, poison and crop without actual experiment.

The growth of flax was greatly impeded on a manganese‐deficient fen soil, and the molybdenum toxicity was masked in consequence. When the deficiency was corrected the poisonous effect of molybdenum on this soil was very marked, even with the lower dressing.

The composting of loam with peat usually, but not invariably, resulted in a reduction of the toxicity of molybdenum. The different results obtained with several crops on a variety of soils still yield no definite clue to the factors which determine the relative toxicity of molybdenum to plant growth and such points as soil acidity, response to climatic conditions and nutritive deficiencies are among those which need further investigation.
Studies on the Relationship Between Earthworms and Soil Fertility
Authors: Guild By W. J. McL.
Published: February 2008

Observations on earthworm populations in the Carse of Stirling indicate that there are definite differences according to soil type both in total population numbers and in the relative numbers of each species present. The light and medium loams appear to carry higher total populations than the heavier clay types or the more open gravelly sand or alluvial types. Within and between the respective soil‐type populations, species numbers are variable, but the actual numbers present on a soil type do not necessarily indicate the relative importance of each species. In all cases Allolobophora caliginosa is the dominant species, being more numerous on the light loam than elsewhere. A. longa is subdominant and forms a substantial percentage on the medium loam and clay. On the light loam A. longa is high in number, but forms a smaller percentage of the total population because of the abundance of A. caliginosa. A. longa is also of reduced importance on the open soils—gravelly sand and alluvium. This species does not differ very much from Lumbricus rubellus and L. terrestris, as a percentage of the population on these two later soils and the light loam. The percentages of these two species are similar within populations, though much lower on the clay than on the other soils, and the total Lumbricus population number is highest on the light loam and lowest on the clay. There is a fair similarity between the two populations on the two open‐textured soils, in both numbers and percentages.

Areas of acid, natural pastures contain earthworm populations low in number and species variety. Some of the species typical of these areas are small active species, e.g. Dendrobaena rubida, D. octaedra and Bimastus eiseni, which are not found in well‐established field populations. When agricultural treatment improves an area the acid‐pasture species eventually decrease in relative number and importance as the species normally associated with good pasture land become established and build up their populations.
The Formation of Insecticidal Films on Building Materials
Authors: Hewlett P. S.
Published: February 2008

The success of size and gelatin as pretreatments was not confined to films of pyrethrins in oil. Pretreatment of cement with 10 % w/v size and 5 % w/v gelatin greatly prolonged the toxic life of films formed by other insecticides in oil solution.

The effects of adding different substances to size and gelatin solutions as pretreatments were investigated. 5 % w/v size or gelatin solutions containing suspended lime or distemper powder were, with the exception of gelatin containing distemper, less effective pretreatments than size or gelatin solutions alone. Magnesium silicofluoride, benzoic acid and salicylic acid, at concentrations up to 0.5 % w/v, appear suitable as preservatives for 5 % w/v gelatin. These three substances are, however, unsuitable for inclusion in size solutions, as they cause precipitates to form. Glycerin or turkey‐red oil at concentrations of 0.5 % v/v, appear suitable as plasticizers for inclusion in both 5 % w/v size and 5 % w/v gelatin solutions.
D.D.T. Impregnation of Sacks for the Protection of Stored Cereals Against Insect Infestation
Authors: Parkin E. A.
Published: February 2008

Cotton flour sacks, jute flour sacks, jute bran sacks and jute grain sacks have been impregnated with 1 and 5 % by weight of D.D.T. Treated and untreated sacks, each containing 1 cwt. of a mixture of grain (5 parts) and weatings (1 part), were exposed to severe infestation by adults of Calandra granaria, Tribolium castaneum, Ptinus tectus, Oryzaephilus surina‐mensis and Ephestia elutella. After storage for 15 weeks at a mean temperature of 21.3d̀ C. and a mean relative humidity of 65 %, the numbers of adult insects in each sack were determined by sieving the contents.

The results with Ephestia elutella were inconclusive. The results with the four species of beetles showed that the eventual degree of infestation of the contents of the sacks was dependent upon the closeness of weave and the D.D.T. content of the sacking material. Impregnation of sacking with 1 % of D.D.T. should afford adequate protection against insect infestation to clean bagged goods stored in stowages which are not heavily infested. Impregnation with 5 % of D.D.T. should offer a very high degree of protection at all times and can almost entirely prevent infestation, if the treated material is of sufficiently close weave to afford some mechanical hindrance to penetration by insects.
Varietal Resistance of Flax to Disease
Authors: Colhoun John
Published: February 2008

Field experiments, using contaminated seed, have been carried out from 1941 to 1947 to study the reaction of a wide range of both fibre and oil varieties of Linum usitatissimum to attack by Polyspora Lini Laff., Colletotrichum linicola Pethybr. & Laff., Phoma sp. and Melampsora Lini (Ehrenb.) LéV. The tests made with Colletotrichum linicola were supplemented by direct inoculation experiments with young seedlings grown under greenhouse or laboratory conditions.

None of the varieties tested proved to be immune to attack by Polyspora Lini, Colletotrichum linicola or Phoma sp. Herkules, Concurrent, Hindi, La Plata, Saginaw x Ottawa 770 B and Winona x Ottawa 770 B were resistant to the stem‐break and browning phases of attack by Polyspora Lini; Bison, Hindi and La Plata were resistant to attacks by Colletotrichum linicola, while Hindi and La Plata showed some resistance to Phoma sp. Immunity or a ‘high’ measure of resistance to attack by Melampsora Lini was exhibited by Formosa, Stakhanovets, Textilshchik, U.S.S.R. No. 2 (ex Dugejheshchya), Wada, Argentine Selection (C.I. 112), Baladi, Bolley Golden (C.I. 644), Bombay (C.I. 42), Hindi, Italia Roma (C.I. 1005–2), J.W.S. (C.I. 708–1), Koto (C.I. 872), Kenya (C.I. 709–1), La Plata, Newland (C.I. 188), Ottawa 770B (C.I. 355), Pale Blue Crimped (C.I. 647), Tammes Pale Blue (C.I. 333–1), Williston Golden (C.I. 25–1) and C.I. 836.

All varieties did not show the same reactions to stem‐break as to the browning phase of attack by Polyspora Lini and similar differences were noted in the case of the uredospore and teleutospore stages of Melampsora Lini. In certain varieties the stems showed a greater resistance to attack by Polyspora Lini or Melampsora Lini than the leaves.

Seeds of all varieties tested in the field experiments became heavily attacked with Polyspora Lini (except in La Plata), Colletotrichum linicola and Phoma sp.
Studies in the Diagnosis of Mineral Deficiency
Authors: Goodall D. W.
Published: February 2008

Material from four fertilizer trials on barley in Hampshire was analysed with the principal purpose of comparing the extent to which the potassium content of different plant organs was diagnostic of potassium deficiency. Samples of older leaf blades and sheaths, young leaves, stems and ears were gathered at the time of ear emergence from each of the 108 plots, and analysed spectrographically for calcium, iron, magnesium, manganese, potassium and sodium.

Differences in composition between plants from the different sites were proportionately greater in the older leaf blades than in the other organs for calcium, the young leaves for manganese and sodium, and the older leaf blades and sheaths for potassium. Differences in sodium and manganese content at the different sites appeared to be related to the differences in potassium status.

Applications of muriate of potash increased the potassium content of all organs except the ears, and decreased the content of magnesium, manganese and sodium, and of iron at one site. The effect of potassium supply on manganese and sodium content was most marked in the young leaves. The proportional increases observed in potassium content as a result of application of muriate of potash were similar at all four sites, in spite of the fact that responses in growth and yield differed greatly.

As between the four sites, the responses to muriate of potash observed in the yields of grain are significantly correlated with the potassium content of the older leaf blades and the stems, and the following tentative limiting values are put forward, above which no increase in grain yield as a result of potassic manuring may be expected:

(a) in the older leaf blades at the time of ear emergence 0.92% potassium in dry matter, (b) in the stems at the time of ear emergence 1–01 % potassium in dry matter.
THE GERMINATION OF MOULD SPORES AT CONTROLLED HUMIDITIES
Authors: SNOW D.
Published: February 2008

Observations have been made on the influence of humidity on spore germination, the rate of elongation of the germ tubes and the production of asexual and sexual fructifications of various mould fungi. The humidity range at which the different species developed is given. Some of the Mucorales and certain pathogenic moulds required high humidities (100‐93%) for their successful growth. Penicillium spp. had a wider humidity range (100‐80%). Aspergillus spp. were able to grow under conditions of even more restricted moisture supply. Spores of members of the A. glaucus group, particularly, germinated and developed at humidities as low as 70‐64%. The reasons for variations in the humidity range of the different species are discussed. The influence of the supply of nutrients on spore germination and subsequent mould growth is considered.
RESOLUTION OF STRAWBERRY VIRUS COMPLEXES: III. THE ISOLATION AND SOME PROPERTIES OF VIRUS 3
Authors: PRENTICE I. W.
Published: February 2008

Aphids (Capitophorus fragariae Theob.) allowed to feed for several days on a strawberry plant with severe crinkle transmitted two viruses. The isolation and properties of one (virus I) have already been described. The other (virus 3) was separated by transferring the aphids to fresh indicators after 24 hr.

Virus 3 was transmitted by aphids which had been allowed to feed on an infected plant for 6 days or more and persisted in the vector for several days. There was some evidence that the virus has a latent period in the vector. The symptoms produced by virus 3 on Fragaria vesca and Royal Sovereign strawberry are described.

On Royal Sovereign, viruses 1 and 3 together produced symptoms of severe crinkle and viruses z and 3 together produced yellow‐edge. A form of severe crinkle is thus shown to be caused by a virus complex which can be resolved by means of the vector, and severe crinkle is shown to be etiologically distinct from mild crinkle.
STUDIES IN THE DIAGNOSIS OF MINERAL DEFICIENCY: V. MANGANESE DEFICIENCY IN WHEAT
Authors: GOODALL D. W.
Published: February 2008

At fourteen sites where winter wheat was growing commercially, twelve of which were known or suspected to be deficient in manganese, a spray of manganese sulphate was applied late in the shooting stage of development, and the effect on yield of grain estimated. Samples of certain organs of unsprayed wheat plants were gathered on three occasions between tillering and ear emergence, and samples of weed leaves on the same occasions and after harvest; these samples were analysed spectrographically for manganese.

The results indicate that analysis of the wheat plant can be used to forecast its response to a manganese sulphate spray, and the following tentative limiting values for manganese content are put forward, above which no increase in grain yield as a result of treatment may be expected: (a) during tillering, 34 p.p.m. manganese in dry matter of lower leaf blades; (b) just prior to ear emergence, 36 p.p.m. manganese in dry matter of stems. The highest correlation obtained between response and manganese content was that with the values for stem samples gathered just prior to ear emergence.

Analysis of weed samples can only be expected to indicate gross differences in the manganese status of different sites.
A THREE YEARS‘ SURVEY OF POTATO APHIDS IN NORTH‐EAST YORKSHIRE
Authors: FIDLER J. H.
Published: February 2008

This paper considers the suitability of north‐east Yorkshire as a centre for the production of high‐grade seed potatoes, taking the number of aphid vectors of virus diseases as the criterion. Counts of aphids were made during three consecutive seasons on selected fields on the higher land in this area. These counts are related to the various geographical, climatic and biological factors found in each field and conclusions are drawn as to the most suitable districts within the area and the type of field which is likely to prove most satisfactory for this crop.
EXPERIMENTS WITH INSECTICIDAL SMOKES FOR INDOOR USE
Authors: BUSVINE J. R. , KENNEDY J. S.
Published: February 2008

Insecticidal smoke generators were tested in the laboratory and in practice. Each generator contained 110–120 g. of crude insecticide, either D.D.T. or benzene hexachloride. Over half the insecticide was evolved unchanged as a smoke of particles less than 1 μ in diameter, by a slow combustion mixture. In the laboratory tests, the generators were used at the rate of one to 1800–2500 cu.ft. (50–70 cu.m.). Benzene hexachloride had a greater initial insecticidal effect and a better residual action up to a week after treatment; thereafter (1 and 6 months) the D.D.T. was more effective. The residual effects of horizontal surfaces were good against bedbugs, but the deposits on vertical surfaces were not highly efficient. Residual action against mosquitoes of vertical surfaces a week after treatment was fair, but effects of inverted surfaces were poor.

The deposits of active insecticide on horizontal surfaces were about 15–30 mg./sq.ft.; on vertical surfaces, 3–10 mg./sq.ft.; and on inverted surfaces, 2–6 mg./sq.ft.

A field trial was conducted between August and November in kitchens infested by flies and cockroaches. The generators were used at the rate of one per 64 cu.ft. (18 cu.m.). A substantial reduction of flies for 11 weeks was obtained by D.D.T., but for only 2 weeks with benzene hexachloride. Both treatments reduced heavy cockroach infestations to negligible proportions for 2–3 months. There was evidence of some repellent effect.

Thermal generators require careful precautions to prevent indirect tainting of food or beverages. They are very wasteful of insecticide especially since two or perhaps three treatments per season might be necessary. This would use twenty times as much insecticide as a spray treatment. On the other hand, labour and equipment costs are somewhat lower, and ease of operation very much greater, with smoke generators.
DOSAGE‐MORTALITY CORRELATION WITH NUMBER TREATED ESTIMATED FROM A PARALLEL SAMPLE*
Authors: WADLEY F. M.
Published: February 2008

When the number of organisms treated in a dosage‐mortality study is not known exactly, but is estimated from a sample, weighting must be modified. Weights based on Poisson expectation are worked out and tabled. Maximum likelihood equations, designed to improve the estimate of number treated, are presented. Two numerical examples are worked out to illustrate the use of the weights and equations.
THE TRANSMISSION OF SUGAR‐BEET YELLOWS VIRUS BY MECHANICAL INOCULATION
Authors: KASSANIS B.
Published: February 2008

Sugar‐beet yellows virus, hitherto transmitted only by aphides, can be transmitted mechanically to sugar‐beet if a suitable abrasive is used. Most inoculated leaves develop local lesions, but systemic infection usually occurs in only 10% of the inoculated plants. Systemic symptoms develop more slowly than in plants infected with aphides.
OBSERVATIONS ON A VIRUS DISEASE OF COWPEA IN TRINIDAD
Authors: Dale W. T.
Published: February 2008

A mosaic of cowpea and asparagus‐bean (Vigna unguiculata) is common in Trinidad. The same virus sometimes attacks Cajanus indicus, Crotalaria juncea, Glycine max, Phaseolus mungo and P. aureus, usually when growing near to infected cowpeas. Desmodium frutescens, Psophocarpus tetragonolobus, Sesbania speciosa, Vigna vexillata, Phaseolus trinervius and varieties of P. Iunatus are also susceptible to systemic infection. Most of the above give local lesions, which are the only symptoms produced on Canavalia ensiformis and Dolichos lablab. No infections were obtained on Phaseolus vulgaris, or on any plant outside the Leguminoseae.

The virus is seed‐borne in asparagus‐bean, but apparently not in tested cowpea varieties. The leaf beetle Ceratoma ruficornis is a vector, and is probably largely responsible for spread in the field; Aphis medicaginis seems unable to transmit the disease. The thermal inactivation‐point of the virus is 66°C., its dilution end‐point 1: 100,000, and longevity in vitro over 20 days.
THE GROUPING AND OVERWINTERING OF MYZUS PERSICAE SULZ. ON Prunus Species
Authors: Broadbent L.
Published: February 2008

The aphid Myzus persicae Sulz. overwintered successfully on an almond‐peach hybrid for three consecutive years. Experiments provided no evidence in favour of the theory that the olfactory sense is used by aphids to find their host, nor were flying aphids attracted to other M. persicae or to honeydew on the host. Having found their host, presumably by chance, alate gynoparae tended to associate in groups.
EFFECT OF PREVIOUS CROPS ON THE INCIDENCE OF EYESPOT ON WINTER WHEAT
Authors: Glynne Mary D. , Moore F. Joan
Published: February 2008

Surveys of winter wheat from 1939 to 1946 show that eyespot (Cercosporella herpotrichoides Fron.) occurs throughout Britain and that its incidence depends largely on previous cropping and on weather. Examination of 551 crops on land whose cropping for the previous 4 years was known showed that the incidence rose steadily with increasing numbers of preceding wheat and barley crops: where neither crop had been taken for 4 years the proportion of crops with more than 70% infected straws was 2%, rising to 45% where three or four such crops had been taken and the average straws infected rose from 6 to 55%.

The percentage infection to be expected in various groups of crops was calculated from previous cropping; it was compared with the actual infection and so used to assess the importance of other factors in determining the incidence of eyespot. High spring rainfall, early sowing and a dense plant increased incidence and low spring rainfall, late sowing and a thin plant reduced it.

Eyespot was not usually severe on newly ploughed grassland until the third or fourth crop of wheat, but under very wet conditions it was sometimes severe in the second crop.

Oats is much less susceptible than wheat or barley, but some crops were found with a third of their straws infected.

A brief survey of winter wheat in Holland suggested possible causes for the rise and fall of eyespot in recent years and for its present lower incidence there as compared with East Anglia.
STUDIES OF THE CLOVE TREE I. SUDDEN‐DEATH DISEASE AND ITS EPIDEMIOLOGY
Authors: NUTMAN F. J. , SHEFFIELD F. M. L.
Published: February 2008

Sudden‐death disease of cloves has been present and steadily increasing in both Zanzibar and Pemba for many years. The only premonitory symptom is a slight chlorosis followed by thinning of the foliage and reduction of the absorbing system. Death follows after a period, which may vary from only a few days to many months. Death occurs from lack of water caused by the disorganization of the absorbing roots.

The outbreaks fall into three classes: (1) the sporadic, which ceases to spread after killing a few trees; (2) the ‘Pemba’ type showing clear peripheral spread; (3) the diffuse epidemic type.

In Pemba some 500 small outbreaks are scattered through the clove areas and some seem to be passing from type (2) to type (3). The total number of trees affected there is less than in Zanzibar, where the situation approximates to a single outbreak involving half of the clove‐growing area of the island. The rate of spread of the disease varies, but it is accelerating.

Various causes, physical, physiological, and pathological, have been suggested to account for the condition. The epidemiology suggests that all but a pathogenic hypothesis can be discarded. Of the possible pathogens, a virus carried by a lethargic vector is the most probable. Suspicion is attached to a scale insect which is tended and transported by the red tree‐ant, Oecophylla longinoda.
STUDIES ON POTATO VIRUS X I. TYPES OF CHANGE IN POTATO VIRUS X INFECTIONS
Authors: Matthews R. E. F.
Published: February 2008

In tobacco plants infected with mild strains of virus X, severe strains may arise as mutations which multiply locally.

Several strains of virus X gradually lost infectivity for potato on continued culture in other hosts such as tobacco.

Strains that are poorly infective or invasive for potato may take considerable time to move into the growing shoot from the tuber in detectable amounts.

Pronounced and apparently spontaneous increases in the severity of the strain that dominates in potatoes may occur in field crops.
STUDIES ON POTATO VIRUS X II. CRITERIA OF RELATIONSHIPS BETWEEN STRAINS
Authors: Matthews R. E. F.
Published: February 2008

The range and type of symptoms produced by strains of virus X are briefly described.

Of ten strains examined, six were identical in serological cross‐absorption tests, and two (T.B.R. X and B) differed considerably from the others. The possibility of preparing strain‐specific antisera is indicated.

The protection afforded by mild strains against severe strains in tobacco and Datura tatula was complete for all strains tested except T.B.R. X and B, which gave only partial protection. Thus there is a correlation between wide serological differences and a breakdown in the protection afforded in the plant.

There was no correlation between type of symptoms caused and serological relationships.

There was some evidence to show that strains from the same source were more closely related than strains from different sources.
COLORADO BEETLE IN THE CHANNEL ISLANDS, 1947 AND 1948
Authors: DUNN E.
Published: February 2008

Colorado beetles can survive up to 10 days in sea water and still be capable of flying when the temperature reaches 80° F. (26·67° C.). The beetles that reached the Channel Islands in May 1947 and in May 1948 prove that they can travel across about 30 miles of sea, the approximate distance of Guernsey from the Cherbourg peninsula. The invasions occurred as a result of migrant beetles from the Cherbourg peninsula which dropped on the sea between the Channel Islands and the French coast and drifted ashore.
TWO SPECIES OF APHELENCHOIDES ASSOCIATED WITH STRAWBERRY BUD DISEASE IN BRITAIN
Authors: FRANKLIN MARY T.
Published: February 2008

Two species of Aphelenchoides have been found in nematode‐diseased strawberries from several places in Britain. They are identified as Aphelenchoides fragariae (Rit‐zema‐Bos, 1891) and A. ritzema‐bosi (Schwartz, 1911) and the differences between them are fully discussed. A. olesistus (Ritzema‐Bos, 1893) is considered a synonym of A. fragariae (Ritzema‐Bos, i89x).
THE INSECTICIDAL ACTIVITY OF SOME SYNTHETIC ORGANO‐PHOSPHORUS COMPOUNDS
Authors: EATON J. K. , DAVIES R. G.
Published: February 2008

The toxicity of a series of organo‐phosphorus compounds to the overwintering eggs of Aphis pomi Deg., Operophtera brumata (L.) and Metatetranychus ulmi (Koch) was examined by a laboratory technique. The eggs of M. ulmi were highly resistant to all the compounds tested, those of Operophtera brumata were most susceptible to P‐nitrophenyl diethyl thionphosphate (E 605) and those of Aphis pomi to p‐nitro‐phenyl diethyl phosphate (E 600). With analogues of the last‐mentioned compound there is evidence that their toxicity to A. pomi eggs is associated with the presence of electron‐attracting substituents in the benzene nucleus. A number of organo‐phosphorus compounds, including hexaethyl tetraphosphate and p‐nitrophenyl diethyl thionphosphate, were highly toxic under laboratory conditions to the active summer stages of Metatetranychus ulmi, but the summer eggs of this mite were rather more resistant. Field trials of hexaethyl tetraphosphate and p‐nitrophenyl diethyl thionphosphate for the control of the aphids Brachycaudus helichrysi (Kalt.), Phorodon hutnuli (Schr.) and Aphis pomi Deg. showed these substances to be effective substitutes for nicotine.
THE SPREAD OF VIRUS DISEASES TO SINGLE POTATO PLANTS BY WINGED APHIDS
Authors: BROADBENT L. , CHAUDHURI R. P. , KAPICA L.
Published: February 2008

Young potato plants in pots exposed in the open near plots of potatoes for limited periods at intervals during the summer, became infested with large numbers of winged aphids only during warm, calm and dry weather. Although visited by aphids during May and June, when much of the spread of viruses occurred in nearby potato crops, few of the potted plants became infected. Most potted plants became infected in July when alate aphids were leaving neighbouring potato crops. Widely different proportions of the exposed plants became infected in different years; in two of the three years, many more plants were infected with virus Y than with leaf roll virus.
THE INFECTION OF PLANTS BY VIRUSES THROUGH ROOTS
Authors: ROBERTS F. M.
Published: February 2008

Roots of young tomato plants became infected when inoculated with tomato bushy stunt, tobacco mosaic, and potato X viruses. Root infections also occurred when these viruses were added to soil or culture solutions in which plants were growing.

The viruses were sometimes localized around their initial entry points in roots; sometimes they invaded the root system but not the shoots, and sometimes they produced full systemic infection of roots and shoots. In some experiments, but not all, systemic infections were more frequent when the upper tap root or superficial roots were inoculated than when fibrous roots were inoculated.

In both tomato and potato, virus X spread from diseased to healthy plants sharing the same culture solution, if their roots were in contact, but not otherwise. Infection of the roots of potato plants by inoculation, produced only one plant with virus‐infected haulms, although several had infected tubers.
OBSERVATIONS ON BLINDNESS IN OATS
Authors: SHEALS J. G.
Published: February 2008

The relative importance in North Wales of various factors said to cause blindness in oats was investigated. It is concluded that a direct attack on the developing panicles by frit fly larvae and by adults and larvae of thrips was of little importance in causing the blindness encountered. Most of the blindness appeared to result from adverse physiological conditions probably operative during early growth. Varying varietal susceptibility to blindness was noted, and the effect on the subsequent panicles of an early insect attack on the vegetative parts of the plant is discussed.