bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct microscopical observations upon the rumen population of the ox
Authors: Baker Frank
Published: February 2008

The rumen population of the ox comprises three major groups of micro‐organisms:(a) Protozoa, (b) iodophile micro‐organisms, (c) aniodophile micro‐organisms. The iodophile species comprise macro and micro forms. The forms include several new species and genera which are described in the paper. A fixed and a free iodophile population are discriminated, the former constantly attached to starch grains and vegetable fragments, the latter in suspension in the rumen liquid. The rumen population was qualitatively independent of the range of diet and of the breed of animal examined. Protozoa play no part in the decomposition of cellulose but digest starch. Decomposition of both starch and cellulose is accomplished by the fixed iodophile microflora which, in the process, synthesize iodophile polysaccharide. During passage through the alimentary canal the rumen population is eliminated, the Protozoa by peptic and tryptic digestion and the iodophile microflora by (a) digestion by Protozoa, (b) autolysis, (c) action of digestive enzymes. The products of microbial synthesis are held to be assimilated by the host animal.
A film technique for the biological evaluation of pyrethrum‐in‐oil insecticides for use against stored product insects in warehouses
Authors: Parkin E. A. , Green A. A.
Published: February 2008

There is need for a technique whereby a given insecticidal preparation can be compared with a standard containing 0.8% (w/v) pyrethrin 1 in a heavy white oil and pronounced biologically equal or inferior to the standard within known and reasonable limits. A film method was investigated, Tribolium castaneum beetles being used as the test insects.

Numerous factors which may influence the kill achieved are discussed. The results of preliminary work, planned to help in the standardization of some of these factors, are summarized.

Several materials were tested to ascertain their suitability for reception of the insecticidal film and, as thin greaseproof paper showed promise, its possibilities were explored. Although 0.3 % pyrethrin I could be distinguished from 0.4%, 0.5% could not be distinguished from 0.8%, and the results throughout were very heterogeneous.

Woven Nylon proved more satisfactory, since the test just failed to establish a significant difference between 0.6 and 0.8% pyrethrin 1. The origin of a pink coloration of the substrate, when T. castaneum beetles were confined on Nylon sprayed with pyrethrum in oil, was investigated.

Whatman filter paper no. 544 proved the best substrate, and a comparative test on it will distinguish 0.65% pyrethrin 1 from the standard 0.8%; the limit could probably be raised to 0.7%.

The influence of several factors on the homogeneity of the results was investigated, and the importance was shown of allowing beetles time to recover from the mechanical shock inherent in the method of counting into batches.

Directions are given for carrying out the film technique for comparing preparations of relatively high pyrethrin content. The method does not measure the direct spray or fumigant action of the insecticide.

The technique described is compared with the Peet‐Grady method for evaluating liquid household insecticides of low pyrethrin content. A simplified, but less accurate, design for the test is indicated.
Studies in the physiology of the onion plant
Authors: Heath O. V. S.
Published: February 2008

This paper completes the survey of the effects of five factors on flowering behaviour, bulbing, and ripening of onions grown from sets (Heath, 1943) and deals with the factors day length and temperature in the second season. The results from both papers are discussed and the main conclusions are as follows: Flowering is greatly reduced or completely inhibited by submitting the plants to high temperature whether (1) during the whole period of growth from seed to set, (2) during the first part or whole of the storage period (Oct.‐Mar.), or (3) throughout the second season of growth from set to mature onion bulb. Unless very high temperature (35d̀; C.) is reached, heat storage restricted to the last part of the dormant period may only delay but not reduce flowering. Cold storage (od̀; C.) throughout or for the first part of the storage period reduces flowering; when restricted to the last part it tends to increase bolting, but at any other period in the life history of the onion plant bolting is apparently favoured by medium temperature (10–15d̀ C). Long days (16 hr.) throughout the second season inhibit inflorescence emergence irrespective of temperature within the range investigated. Conditions of day length and temperature in the second season favourable to bulbing are inimical to flowering: thus both long days and high temperature tend to encourage bulbing and prevent bolting, while short days inhibit bulbing but allow of bolting if the temperature is not too high. Late planting of sets in the field therefore reduces bolting. Leaf emergence ceases abruptly when bulbing begins at high temperature, and even at low temperature few if any more leaves expand. The relation of this fact to optimal time of planting and the use of American varieties capable of bulbing in short photoperiods is discussed. Seedlings apparently need a longer photoperiod for bulbing than plants grown from sets. A day length just adequate for bulbing at high temperature will not allow of bulbing at low temperature, with the result that seedlings sown very late produce good bulbs at high temperature but may fail to bulb at low temperatures. High‐temperature storage, especially during the last part of dormancy, tends to the production of distorted leaves, especially when followed by growth of the sets at high temperature. Such plants show a high mortality. Heat storage also delays and restricts bulbing, which is reflected in the increased number of expanded leaves. Ripening is similarly delayed; this effect is not directly due to water loss during storage.
Notes on basal rot of narcissus
Authors: Hawker Lilian E.
Published: February 2008

Inoculations in situ of roots of narcissus plants with cultures of Fusarium bulbigenum in early summer gave positive results, as shown by the presence of rotted bulbs at the time of lifting or by subsequent rotting of bulbs in storage. These results were obtained only if the soil was wet at and after the date of inoculation. Cool weather delayed infection. Bulbs planted in the autumn in soil artificially or naturally contaminated with F. bulbigenum gave a complete stand in spring but later showed considerable losses from basal rot.
The reactions of potato varieties to viruses X, A, B and C
Authors: Cockerham George
Published: February 2008

The reactions of 146 potato varieties to graft infection with viruses X, A, B and C are recorded, on the basis of their top‐necrotic or non‐necrotic symptoms. Evidence is given that the viruses B and C used in this work were uncontaminated with other viruses. Reference is made to the effects of varietal reaction on virus distribution.
The stem and bulb eelworm, Anguillulina dipsaci (Kühn, 1858): the importance of collating evidence on the behaviour of biologic strains
Authors: Wilson G. Fox
Published: February 2008

The results of experiments on the infection of many different plants with seven biologic strains of known history of the nematode, Anguillulina dipsaci (Kühn), are given, together with the results obtained by other investigators. The technique by which the nematode was induced to infect other host plants is described in detail. The biologic strain theory in relation to A. dipsaci is discussed, together with the merits of the trinomial system of nomenclature in connexion with unspecialized races. The factors concerned with nematode outbreaks receive consideration. The relationship that exists between flower colour in herbaceous phloxes and the degree of infection by A. dipsaci is presented.
Notes on basal rot of narcissus: III. Eradication of the disease from narcissus stocks by repeated use of formalin in the hot‐water bath
Authors: Hawker Lilian E.
Published: February 2008

Stocks of narcissi infected with Fusarium bulbigenum were divided into two parts, of which one was given the standard hot‐water treatment and the other was hot‐water treated with the addition of 0.5% formalin to the water. Some stocks were lifted the following season and the treatment was repeated. With most stocks a single application of formalin was sufficient to reduce the amount of disease to negligible proportions, but with one heavily infected stock a second treatment was necessary.
The relationships of some viruses causing necrotic diseases of the potato
Authors: Bawden F. C. , Sheffield F. M. L.
Published: February 2008

Potato virus B, and some other viruses with reactions in potato varieties different from any previously described, are strains of virus X. All produce intracellular inclusions which vary with different hosts and virus strains. Except with virus B, the inclusions are larger and more frequent in potato than in tobacco or tomato. All give systemic infection when inoculated to tobacco, tomato and potato varieties in which they are carried or cause mosaic symptoms; some give systemic infection when inoculated to varieties in which they cause top‐necrosis, whereas others give only local lesions.

Potato virus C is a strain of virus Y: in tobacco and a few potato varieties both produce similar symptoms, but in those varieties in which Y causes leaf‐drop streak, C causes top‐necrosis. C causes systemic infection when inoculated to tobacco and to potato varieties in which it causes mosaic symptoms, but not when inoculated to potato varieties in which it causes top‐necrosis. Virus C was not transmitted by M. persicae. Viruses C and Y produce a few small intracellular inclusions in potato and tobacco.

Virus A is not related to Y or X: no inclusions were found in plants infected with A alone.
The use of toxic polynitro derivatives in pest control
Authors: Batt R. F. , Martin H. , Wain R. L.
Published: February 2008

The estimation of dinitro‐o‐cresol in winter washes consisting of petroleum oil, the cresol and emulsifier, must first involve the separation of the cresol from the other constituents present. A method applicable to the cases of emulsions compounded with various types of emulsiner failed when sulphite lye was present, and this was shown to be due to the action on the cresol of reducing sugars in alkaline solution. Avoiding an alkaline extraction until these interfering substances had been effectively removed led to an alternative method by which it was possible to separate D.N.C. in this type of emulsion.

The results obtained demonstrate that the methods described are satisfactory for the routine estimation of D.N.C. in petroleum oil/D.N.C. emulsions.
Occurrence of Ophiobolus graminis var. Avenae on wheat crops in the field
Authors: Dennis R. W. G.
Published: February 2008

Ophiobolus graminis var. Avenae has been found on oat crops in ten counties in Scotland. It has also been shown to attack wheat crops in the same districts.
Inert dust insecticides: Part II. The nature of effective dusts
Authors: Alexander P. , Kitchener J. A. , Briscoe H. V. A.
Published: February 2008

The conditions required in an inert dust for it to become an effective insecticide against grain weevils have been investigated. Particle size and intrinsic hardness are important, but not the only, factors. In the case of carborundum, particles larger than 15μ are without action, probably because they do not adhere to insects, and effectiveness increases as the size is reduced from 10μ to about 2μ where a maximum effectiveness is reached.

The effectiveness of a large number of different substances has been tested by a simple method which eliminates complications arising from particle size differences, and the results show a rough correlation of effectiveness with hardness. In general, materials softer than calcite are ineffective, and effectiveness increases with hardness, but the method of preparation of dusts is also important. Some dry‐ground powders are inferior to those wet‐ground, a phenomenon which appears to be due to some kind of surface change—possibly the formation of a Beilby polish layer. The effectiveness of some dusts can also be considerably altered by superficial chemical treatment.

A theory is proposed, based on an experiment with an artificial membrane system, to explain the mechanism by which dusts promote evaporation of water from insects. It is suggested that clean crystalline surfaces of effective dusts can absorb, or in some way penetrate, the water‐resistant epicuticle.
Inert dust insecticides: Part III. The effect of dusts on stored products pests other than Calandra granaria
Authors: Alexander P. , Kitchener J. A. , Briscoe H. V. A.
Published: February 2008

The inert dusts used in Parts I and II against the grain weevil have been found effective in vitro against a variety of other insects infesting stored products, both larvae and adults. The order, as well as the magnitude, of effectiveness of a series of dusts differs for different species, but the mechanism of action appears to be the same, viz. promotion of evaporation of moisture, leading to death by desiccation. In contrast to the results with Calandra, highly adsorbent dusts like charcoal are much more effective on larvae than are mineral powders.

Dusts have a particularly striking action on the mealworm, and this case has therefore been investigated more fully. Dead mealworms when dusted do not lose water nearly as rapidly as live dusted ones.
Diseases of the gladiolus: II. Experiments on dry rot disease caused by Sclerotinia gladioli Drayt
Authors: Hawker L. E. , Bray R. J. , Burrows T. W.
Published: February 2008

Inoculation experiments show that (1) young corms are more susceptible than old and become less susceptible as they develop, (2) infection of unwounded corms readily takes place, (3) inoculation of the top of an old corm is more effective than that of the side or base.

The percentage diseased new corms produced from infected parent corms varies from o to 100 according to soil conditions. Disease is favoured by wet soil.

Removal of ‘husks’ (leaf bases) increases the susceptibility of corms planted in contaminated soil, but the presence of husks is not an effective control. Dehusking did not increase the number of diseased young corms in an infected stock planted in new soil.

No variety was strikingly more resistant than the rest.

Good control was obtained when, corms of a diseased stock were treated with mercuric chloride, mercurous chloride (calomel) or the proprietary mercury fungicide Aretan. Calomel gave the most consistent results. Various other treatments were tested in small‐scale trials with some success. Red copper oxide, formalin and the proprietary mercury compound, Ceresan, were harmful.

Sterilization of contaminated soil with formalin, mercuric chloride, Aretan or Uspulun gave good but not complete control. Formalin was the least effective.
A comparison of the toxicity of certain dyestuffs to the conidia of Fusarium culmorum
Authors: Dion W. M. , Lord K. A.
Published: February 2008

The toxicity of a number of dyestuffs to the spores of Fusarium culmorum and Cercosporella herpotrichoides was determined by the slide‐germination technique. No attempt was made to distinguish between fungistatic and fungicidal activity.

The toxicity of basic dyestuffs was unaffected by the acid radicle associated with the dye base.

The high toxicity to Fusarium culmorum of malachite green dye base was reduced weight for weight and mole for mole by substitution of ethyl, propyl or butyl groups for methyl groups.

The reduction of malachite green to malachite green leuco base removed toxicity.

The substitution of amino groups and alkylated amino groups in benzene nuclei of triphenyl methane increased toxicity, whereas acid groups reduced toxicity. Sulphonation and carboxylation reduced toxicity to vanishing point.

Alkylation of amino groups increased, but alkylation of benzene nuclei did not affect toxicity appreciably.

When the central carbon atom of the triphenyl methane dyestuffs was replaced by nitrogen (e.g. Bindschedler's green) the diphenyl ammonium compounds were less toxic than the corresponding triphenyl‐methane compounds.

The prevention of rotation of the aminated benzene rings by bridging, in the o‐position to central atom, with O or N, and so obtaining a planar molecule only slightly affected toxicity.

Certain acid dyes stimulated fungal growth.

The toxicity of the basic dyestuffs seems to depend not on one specific part but on the molecule as a whole, and within certain limits the structure may be varied without pronounced changes in toxicity.
Trichloracetonitrile as a fumigant
Authors: Bovingdon H. H. S. , Coyne F. P.
Published: February 2008

The comparative toxicities of trichloracetonitrile to various insects infesting stored products and houses have been determined. The toxicity is increased by the addition of 10% or more of carbon dioxide. In the fumigation of bulk wheat trichloracetonitrile compares favourably with ethylene oxide. Its phytocidal action on seed wheat at doses which might be used in practice is not serious and the vitamin B, and riboflavin contents of wheat are not affected. The possibility of fumigating dried fruit with trichloracetonitrile has been demonstrated. Trichloracetonitrile is highly phytocidal to growing plants.
Observations on the method of transmission of internal boll disease of cotton by the cotton stainer‐bug
Authors: Frazer Helen L.
Published: February 2008

Results are presented to show that all the rules of proof for insect transmission of Nematospora by Dysdercus spp. have now been satisfied: viz. a close association of the insect with diseased plants in nature; visitation of healthy plants by the insect under conditions suitable for transmission of the disease; the presence of the pathogen in or on the insect in nature or following visitation to a diseased plant; and experimental production of the disease by insect visitation under controlled conditions. Hence it is claimed that Dysdercus spp. are proved vectors of internal boll disease of cotton.

Fungal material as spores or mycelium is carried as an external contaminant on the mouth‐parts, although it is located in the deep stylet pouches, where protection is afforded and spore germination is possible.

The fungus is cast off with the exuviae during moulting, but recontamination from exuviae or other sources in the environment occurs.

The transmission is hence purely mechanical with the insect obligatory only in its function as a syringe to inject the fungus which is otherwise unable to reach its substrate. Insect and fungus can develop independently and the insect is apparently unharmed by the presence of the fungus.

Nematospora spores also reach the intestine but do not appear to remain viable there and do not germinate.

The fungus is believed to enter and leave the insect by the same route. The spores are well adapted in shape to reach the stylet pouches of the insect.

No alternative morphological form of Nematospora gossypii within the insect has been found.

The results do not lead to methods of control of the disease beyond those in practice‐trapping of insects, destruction of alternative host plants, and the alteration of time of planting to avoid insect attack.
Changes in wireworm population associated with cropping
Authors: Miles H. W. , Miles M.
Published: February 2008

Data are given to show that the rate of decline of the wireworm population associated with a root crop is not significantly greater than that associated with a cereal crop. Data are given on the wireworm populations of adjoining ley plots over 3‐5 successive years, and indicate a slow rate of increase during the early years.
Field trials of copper fungicides for the control of potato blight I. Foliage protection and yield
Authors: Large E. C.
Published: February 2008

Results are given of eight replicated‐plot trials of a number of copper fungicides in comparison with standard Bordeaux mixture under relatively severe conditions of potato blight incidence, in Devon and Cornwall during the years 1941‐4.

Recent methods of disease measurement on foliage were applied and developed; characteristic curves were obtained defining the conditions of trial and the relations between spray timing and progress of blight attack. The time interval between half‐decay dates for sprayed and unsprayed foliage was taken as a numerical criterion of the direct protective effect of spraying.

A linear relationship was found to hold between probit foliage decay and time, and this was accounted for by the close correspondence of the probit curve to that derived from a growth law, da = Ca(A ‐ a)dt, where a denotes the percentage foliage area affected by blight at time t after the beginning of the attack.

Methods were found for preparing dispersible mixtures of bentonite with active copper compounds for use in spraying. With such admixture, to improve adhesion, both cuprous oxide and copper oxychloride preparations nearly equalled Bordeaux mixture at the same copper dosage. Without sticker, and compounded with water‐soluble dispersing agents, these materials were equalled by Bordeaux mixture at half their copper dosage.

Suspensions of metallic copper were found to have pronounced fungicidal effect against Phytophthora infestans. A bearing of this result on the fungicidal mechanism of cuprous oxide is discussed.

Results from 103 pairs of twice‐sprayed and unsprayed plots of main‐crop potatoes in Devon and Cornwall in 1941‐4 showed a mean prolongation of growth due to spraying of 16 1/2 days, and a mean gain in total yield of 2 3/4 tons/acre; but the gain in yield resulting from a given prolongation of growth varied greatly, according to the stage of crop development at which the prolongation of growth began.

Spray retention data, for correlation with foliage protection and yields, were obtained in all four years.
The competition between barley and certain weeds under controlled conditions
Authors: Mann Harold H. , Barnes T. W.
Published: February 2008

The nature of the competition between barley and certain annual weeds which are dominant at Woburn, under conditions where the available root space as well as the water, light, and nitrogen required by the plants are limited, has been studied. The weeds involved are Spergula arvensis Linn. (spurrey) and Matricaria inodora Linn, (scentless mayweed).

Where there is a limited and fixed root space, and where the amount of available nitrogen is also limited, and where barley or each of the two weeds are grown by themselves, there is a tendency for the yield of the crop or of the weeds to reach a maximum with a definite density of plants per volume of soil. When an excess of nitrogenous fertilizer is added, a limit is reached with each of the weeds where extra nitrogen, added as manure, does not increase the growth but only raises the percentage of nitrogen in the plants as grown.

Where there is a constant amount of weediness, with either of the two weeds studied, an increase in the density of barley plants diminishes the injurious effect of the weeds. The combined weight of barley and weeds is hardly ever as great as that of the barley grown in weed‐free soil. In a mixed crop, the weight of both weeds steadily decreases as the number of barley plants increases.

Where there is a constant number of barley plants per unit area, the increase of either of the weeds does not much effect the yield of barley till the number of weed plants exceeds the number of barley plants. The presence of a strong, well‐grown crop of barley largely reduces the production of spurrey and, to a less extent, that of mayweed. With a constant density of barley and a variable density of weeds, the total weight of barley and weeds, taking the above‐ground portion only, is almost constant whatever be the number of weed plants. Where the mixed plants are grown under slight nitrogen stress, the barley secures the greater part of the nitrogen absorbed, obtaining over 75 % of the nitrogen in the combined crop, even when the number of weed plants is greater than the number of barley plants. This applies to both weeds.

If excess of nitrogenous fertilizer (ammonium sulphate) is added to the mixed crop of barley and weeds, above that which will increase the crop, any reduction in the yield of barley must be due to competition for root space. At the highest level of nitrogen used (which, however, did not apparently reach the maximum that the barley could utilize for increased growth), the reduction in the yield of barley with excess of spurrey present was only 12%: with mayweed, a much stronger competitor, it amounted to 45%.

There is no evidence that with either of the weeds there is any special relationship between barley and the weeds. The effect seems to be only one of competition for root space or for nitrogen when there is not an excess of the latter.
Mould deterioration of feeding stuffs in relation to humidity of storage Part III. The isolation of mould species from feeding stuffs stored at different humidities
Authors: Snow Douglas
Published: February 2008

Isolations were made of mould species actively growing on a variety of feeding stuffs stored at fixed humidities between too and 65% for periods of up to 4 years. The factors influencing the species of moulds isolated were: (1) die relative humidity of the atmosphere; (2) the length of the storage period before the isolations were made; (3) the type and origin of die feeding stuffs from which the isolates were obtained.

A critical humidify existed for each species below which the development of mould spores could not take place. At relative humidities (R.H.) between 100 and 90% a large variety of moulds were able to develop. Members of die Mucorales and the Fungi Imperfecti were not isolated below 90% R.H. and, although ***Pemicillium app. flourished between 100 and 85% R.H., they were not isolated below 75% R.H. ***Aspergilhes app., on the other hand, were able to develop under conditions of very restricted moisture supply. Some members of the A. ***glaucus group were able to grow at humidities as low as 65‐70%.

In general, the moat commonly occurring moulds on the feeding stuffs used in these trials were small ***ascospored species of the A. ***glaucus group, particularly A. ***repens and A. ruber. It is considered that it is these species that will most frequently cause mould damage to feeding stuffs in commercial stores.
Certain aspects of resistance of plum trees to bacterial canker Part I. Some biochemical characteristics of Pseudomonas morsprunorum (Wormald) and related phytopathogenic bacteria
Authors: Erikson Dagny
Published: February 2008

Several strains of Pseudomonas mors‐prunorum (Wormald) and Ps. prunicola (Wormald) isolated from pathological lesions of plum and cherry were studied together with the causal organism of bacterial canker of stone‐fruits in California (Ps. syringae from apricot) and other phytopathogenic bacteria obtained from pear and syringa. Comparison was also made with pseudomonas forms pathogenic to pea, bean, lettuce, and tobacco, and with the common saprophytes Ps. fluorescens and Ps. pyocyaneus. With the exception of two yellow organisms (B. pruni and the Pear 8 strain—the latter, however, very occasionally showing fluorescence), all belong to the green‐fluorescent group of Pseudomonas (Dowson's Group II). On the basis of their dissimilation of C and N compounds a very close relationship has been established between these fruit‐tree and syringa pathogens of the green‐fluorescent group. Ps. mors‐prunorum is not highly specialized in its nutrient requirements but can satisfy its fundamental C and N requirements from a very large variety of simple substances. The only consistent biochemical differentiation shown by Ps. mors‐prunorum (including some of the syringa strains) in comparison with Ps. prunicola (including Ps. syringae from apricot and most of the pear strains) is its more rapid production of add from sucrose. Both the mors‐prunorum and prunicola varieties produce a levan from sucrose, which causes a raised gummy growth on solid sucrose‐containing media. This applies also to Ps. pisi, Ps. tabaci, and Ps. phaseolicola, but is not the case with the weakly pathogenic forms—Ps. marginalis, cerasi (= trifoliorum, from bean), and the saprophytes—Ps. fluorescens and Ps. pyocyaneus.

On the basis of biochemical characteristics, considered apart from host pathogenicity, there is no justification for erecting to specific rank these various levan‐forming. green‐fluorescent, phytopathogenic pseudomonads.
Tyroglyphid mites in stored products Methods for the study of population density
Authors: Solomon M. E.
Published: February 2008

The known methods for detecting the presence of tyroglyphids are described. For coarse materials, such as seeds, sieving is recommended. For flour, it is better to examine exposed surfaces, or to keep samples in glass vessels and examine for the runnels made by mites against the glass. Methods of sampling to provide information about the density and extent of infestations are described. Samples must usually be treated in the laboratory. While methods which do not involve the separation of the mites from the material are referred to, such separation is usually necessary. Mites may be separated from most materials by the modified Berlese funnel method of Chernuishev and Petrova; means of overcoming certain disadvantages are suggested. However, vigorous sieving is recommended for coarse materials, and a flotation method, using dichlorethylene, for fine materials such as flour. It is usually more satisfactory to examine and count the mites than to estimate the numbers volumetrically or gravimetrically. They are counted in a dish containing oil, placed on squared paper under a low‐power microscope. A modification of this method, for dealing with large numbers, is described. Methods of expressing population density are briefly discussed.
Wireworm populations in relation to crop production: I. A large‐scale flotation method for extracting wireworms from soil samples and results from a survey of 600 fields
Authors: Cockbill G.F. , . Henderson V. E. , Ross D.M. , Stapley J H.
Published: February 2008

The wireworm survey in the Eastern Counties revealed many cases where the observed wireworm damage failed to correspond with the estimated field population. A possible explanation for this was the inaccuracy of counts made by picking wireworms out of the soil samples by hand. Tests showed that such methods recovered an extremely variable proportion of the wireworms in the‐ samples and, on the average, only two‐fifths of the larvae were obtained. A modified form of the washing and flotation technique used by Salt & Hollick (1944) was introduced for large‐scale work and is described. By this method, ten samples of soil (4 in. diam. and 6 in. deep) bulked together are examined at a time and can be dealt with at the rate of 13 samples per man per hour with an efficiency of 95‐100% in the extraction of wireworms. The populations estimated on 600 fields sampled between December 1942 and May 1943 have thrown more light on the size and composition of the wireworm population in grass and arable fields. Inspection of the crop results on fields tested by the washing process showed a much closer relationship between wireworm population and wireworm damage than had been obtained by the hand‐sorting method in the previous year.
Verticillium wilt of sainfoin
Authors: Isaac Ivor
Published: February 2008

A wilt disease of sainfoin caused byVerticillium DahliaeKleb. is described, and it is shown that the fungus can penetrate sainfoin seedlings through unwounded roots as well as through ruptures caused by the emergence of lateral rootlets.V. Dahliaewas isolated from naturally infected soil only in June, July and August, although another species,V. nigrescens, was obtained throughout the year.

Comparative studies of the longevity of cultures ofV. Dahliae, V: albo‐atrumandV. nigrescensproved that all are viable for at least 3 years on agar media. On sterilized wheat grainsV. Dahliaedies within 8 weeks after inoculation,V. albo‐atrumandV. nigrescenswithin 12 weeks, while the hyaline variants of the first two remain viable for 6 months.

Evidence was obtained that in artificially inoculated soilV. Dahliaepersists mainly as microsclerotia. The fungus may also exist in the soil as hyaline mycelium or conidia, but only for a relatively short time.

The incidence of this disease in sainfoin is reduced by an increase in soil‐water content, but is unaffected by the application of lime to the soil.
The control of narcissus leaf diseases III. Sclerotinia polyblastis Greg, on Narcissus tazetta var. Soleil d'Or
Authors: Gregory P. H. , Gibson Gordon W.
Published: February 2008

In the extreme south‐west of England Narcissus tazetta grown for the outdoor flower crop is regularly attacked by narcissus fire (Sclerotinia polyblastis). A randomized strip experiment on the variety Soleil d'Or laid down in 1937, in which half the plots were sprayed each season, gave data on the effect of controlling this disease on the number and quality of flowers produced in 1939, 1940 and 1941, and on the weight and grade of bulbs lifted in 1941.

There was an average increase of 26 % in the number of flowers produced on sprayed plots, and a 35% increase in weight of bulbs. There was no evidence of a cumulative improvement because most of the gain in one year appears to have been immediately expended in increased flowers in the following season, but the sprayed plots maintained a higher general level throughout. The quality was improved by spraying, mainly by the addition to the inflorescence of an average of one extra ‘bell’. Although not cumulative, there was a residual effect shown by the increased yield of bulbs in 1041 after a season in which only one post‐flowering spray had been applied.

The effect of treatment on the date of flowering (anthesis) was negligible and its direction depended on the season. In this respect Soleil d'Or differs from Golden Spur, in which spraying induced the marked retardation of flowering noted in 1938 and 1939.
The cereals root eelworm, Heterodera major (O. Schmidt) Franklin, in North Wales
Authors: Thomas I. , Brown E. B. , Willis R. J.
Published: February 2008

The cereals root eelworm Heterodera major (O. Schmidt) is shown to be locally distributed in North Wales, the most heavily infested centres being in the arable districts of the eastern counties of the province. The most severe attacks occurred on oats where the crop had been grown too frequently; wheat and barley were apparently unaffected at the cyst populations encountered.
The shallot aphis, Myzus ascalonicus Doncaster, and its behaviour as a vector of plant viruses
Authors: Doncaster J. P. , Kassanis B.
Published: February 2008

A new species of aphis, Myzus ascalonicus Doncaster, is briefly described, and compared with Myzus persicae Sulz., which it resembles superficially. It has been found on shallots in storage and on onions and other species of plants both in glasshouses and in the open between October and June. Its summer habits and hosts are unknown. In comparative virus transmission tests with M. persicae it was found that Myzus ascalonicus transmits dandelion yellow mosaic virus, which is not transmitted by Myzus persicae; and also cucumber virus I, Hyoscyamus virus III and sugar‐beet yellows virus, all of which are transmitted by M. persicae. Myzus ascalonicus does not transmit the viruses of potato Ysevere etch, lettuce mosaic and sugar‐beet mosaic which are transmitted by Myzus persicae.
Bionomics of the carrot fly (Psila rosae F.) I. The infestation and sampling of carrot crops
Authors: Wright D. W. , Ashby D. G.
Published: February 2008

The headlands of a carrot field are generally more heavily attacked by carrot fly larvae than the remainder of the field.

The methods of sampling a carrot crop are outlined: it has been found that, for fields up to 10 acres, samples of carrots taken in alternate twos and threes in the midfield, and in twos on the headlands, give a reliable measure of the infestation. For larger fields the number of carrots is doubled. Transects of headlands and whole fields have been made, and are useful in showing the actual amount of damage in a crop. Thus it is possible to represent each field as a three‐dimensional body showing the amount and distribution of the attack.

The deterioration of attacked carrot crops during autumn and winter has been followed. Deterioration is measured by (1) percentage carrots attacked, (2) number of mines per 100 carrots and (3) the percentage of carrots unsaleable or unfit for market. The relations between (1) mines per 100 carrots and time, (2) percentage attack and time, (3) mines per 100 carrots and percentage attack, and (4) mines per 100′carrots and percentage unsaleability are stated. Based on the above relationships, methods of prediction of deterioration have been worked out.

The importance of shelter in determining the degree and position of attack is discussed and the relative effects of different types of shelter on infestation are compared.
A study of the distribution of the swede midge (Contarinia nasturtii Kieffer) in Devon and symptoms of its attack on various host plants
Authors: Thomas D. C.
Published: February 2008

A survey of swede midge damage in Devon is described, showing that the attack on cow cabbage is most severe in the north and west of the county, while attack on swedes is heaviest in the south and east of the county; the causes of this phenomenon are considered. The life history of the insect is discussed in relation to farming procedure with various crops. Short descriptions and photographs are given of the general symptoms of damage by the midge on the more important cruciferous crops.
The toxicity of certain aliphatic chlorinated hydrocarbons to Calandra granaria L. and other insects infesting grain
Authors: Parkin E. A.
Published: February 2008

An account is given of the biological data obtained during an investigation into the possibility of using certain aliphatic chlorinated hydrocarbons for fumigation of empty grain sacks infested by insects.

The relative toxicity of three mixtures of chlorinated hydrocarbons to adult Calandra granaria, was ascertained: the best contained 3 parts ethylene dichloride and 1 part tetrachlorethylene by volume. Among seven species of insects likely to occur in empty sacks, the resistance of C. granaria adults to the 3: 1 mixture was exceeded only by that of Trogoderma granarium larvae. The toxicity of the mixture to C. granaria was determined over a range of concentrations and periods of exposure: at 20d̀ C and 70% R.H. a concentration × time product of about 1500 mg.‐hr./l. was required for 100% kill. These results were confirmed by inserting tubes containing weevils into bundles of sacks, which were then exposed to fumigant in a steel bin.

The toxicity to adult C. granaria of mixtures containing different proportions of ethylene dichloride and tetrachlorethylene increased as the proportion of ethylene dichloride increased. The toxicity of tetrachlorethylene to the weevils was very low in relation to that of ethylene dichloride.

The concentration × time product for 100 % kill of C. granaria at 20d̀ C. by ethylene dichloride alone was about 1100 mg.‐hr./1. The products for 50 % kill of C. granaria at 10, 15, 20 and 25d̀ C were in the proportion of 3.0: 2.0: 1.0: 0.7 respectively.

Weevils which recovered from severe narcosis by the 3: 1 mixture were able to lay viable eggs.
The quantity and distribution of spray collected by insects flying through insecticidal mists*
Authors: David W. A. L.
Published: February 2008

When a housefly (Musca domestica L.) or the yellow‐fever mosquito (Aëdes aegypti L.) flies through a finely dispersed insecticidal mist a large proportion of the dose accumulated is found on the wings. If Sudan III is added to the insecticide the dye either penetrates into the wings directly and later appears in the malpighian tubules or it may be removed during the cleaning processes and absorbed through the legs.

A colorimetric method of estimating the quantity of spray accumulated by flying insects is described, and it has been employed to investigate the effect which changes in the properties of the mist dispersions and the behaviour of the insects have on the quantity of spray accumulated. Briefly it may be said that within limits the dose accumulated increases with the activity of the insect and the size of the mist particle. The method has also been used to measure the surface median lethal doses of pyrethrins, 2:2‐bis (parachlorophenyl)‐1: 1:1‐trichlorethane (D.D.T.) and 1:2:3:4:5:6‐hexachlorocyclohexane (666) to Musca and Aides.
Tyroglyphid mites in stored products. Nature and amount of damage to wheat
Authors: Solomon M. E.
Published: February 2008

The paper describes experiments and observations on the damage done by mites to stored grain, and methods of assessing the damage. It is confirmed that mites cannot penetrate grains if the grain‐coat is intact; but usually less than 10% of the grains are so intact.

In laboratory experiments, mites consumed up to 3% by weight of the grain before dying out; they were able to destroy the germ completely, but consumed very little of the remainder; the maximum rate of consumption observed over a 5‐week period was 0‐29% of grain weight per week; when added to grain at 75% relative humidity in the proportion of 1% by weight, mites consumed 1% of the grain in 27 days at 21d̀ C, or in 37 days at 10‐15d̀ C. Although mites consumed the grain more rapidly at higher temperatures or humidities, they survived longer at lower temperatures or humidities, and finally did more damage. Mites consumed wheat germ flakes more rapidly than grain, and finally reduced its weight by 74‐85%.

A system of symbols to represent degrees of damage to grain by mites, assessed visually, is presented, and approximate values for the equivalent weight losses are given. The relationship between the product, no. of mites per 100 ex. grain × time in weeks, and the degree of damage to grain, was calculated from experimental data; the damage done per unit of this density × time product was 2‐2‐5 times higher at 25 than at 5‐9d̀ C, and about 1‐4 times higher at 70 than at 90% relative humidity. The mean density × time value corresponding to 1% loss of grain weight was 526,000 at 250 C, and 1,765,000 at 5‐9d̀ C.

Data from granary investigations show the degree of damage associated with various levels of population density and grain moisture. In infested storages, the amount of embryo material destroyed ranged from less than 1% of the total (bulk grain) to about 15% (grain in bags).

Mites may cause a rise in the temperature or moisture‐content of grain, or an increase in the growth of microorganisms; but there is no evidence to suggest that serious damage from these causes is likely except that dense infestations can cause heating.
The design and performance of an atomizing nozzle for use with a spraying tower for testing liquid insecticides
Authors: Hewlett P. S.
Published: February 2008

A nozzle, P.I.L. No. AN2, has been designed for, and used successfully in, the biological assay of insecticides in a heavy oil solution. This new nozzle is easier to adjust and gave a standard deviation of deposit one‐seventh of that given by the nozzle described by Potter (1941).
A survey of potato aphides in north‐west Derbyshire, 1945
Authors: Broadbent L.
Published: February 2008

Counts of aphides infesting potato crops in north‐west Derbyshire at altitudes between 340 and 1360 ft. were made during the summer of 1945. Mysus persicae was abundant on almost all crops, and peak figures on some reached over 1500 per 100 lower leaves. In many fields two peaks were noted, one towards the end of July and the second in mid‐September, and in some fields there were still heavy infestations when the haulms died. The number of aphides varied considerably from field to field; sheltered fields were the least infested. In this area in 1945 there was no evidence to support the contention that the altitude and aspect of the field have any influence on the intensity of infestation. Tuber samples from six fields showed that there was a considerable spread of leaf roll.
The formation of insecticidal films on building materials: I. Preliminary experiments with films of pyrethrum and D.D.T. in a heavy oil
Authors: Parkin E. A. , Hewlett P.S.
Published: February 2008

The relative toxicity to the flour beetle, Tribolium castaneum Herbst, of films of 1‐6% w/v total pyrethrins or 0.8% w/v technical D.D.T. in Shell Oil P31 sprayed on to some common building materials has been investigated. Beetles were exposed on films for 6 days, starting 24 hr. after application of the insecticide, and relatively low kills were recorded even with deposits two to three times as heavy as those normally used in practice. The materials could be placed in order, according to the toxicities of the films formed on them, as follows:

1.6 % pyrethrins 0.8 % D.D.T.

Rough deal, sacking Rough deal, limewashed brick Films more toxic

Fletton brick Fletton brick

Wallboard

Cement, cement‐sand, limewashed brick ceiling board, Cement, cement‐sand Films less toxic

An experiment carried out under practical conditions confirmed the low toxicities of films formed on limewash and wood.

The effect has also been investigated of pretreating bricks with six substances, which might influence the rate of sorption of the oily insecticide into the substrate. Pretreatment with polyvinyl alcohol, starch paste, size, and waterglass greatly increased the toxicity of pyrethrum films on brick, but water and calcium chloride failed to do so. The toxicity of a pyrethrum film on cement‐sand blocks was also very greatly increased by a pretreatment with starch paste.
A mosaic disease of cowpea (Vigna sinensis Endl.)
Authors: Yu T. F.
Published: February 2008

A mosaic disease of cowpea (Vigna sinensis Endl.), prevalent in the bean‐growing regions of China, is described.

The characteristic symptoms of the disease are conspicuous mosaic patterns, deformation and distortion of leaves and stunting of the plant.

The cowpea mosaic virus is transmitted by Aphis rumicis L., Macrosiphum pisi Kalt. and Aphis gossypii Glov. It is also transmitted by artificial juice inoculation. The virus is seed‐bome. It withstands ageing m vitro for 3 days at 220 C. Its inactivation temperature is approximately 62° C. its tolerance to dilution is about 1: 3000.

Cowpea mosaic virus infects lima bean and Adzuki bean in addition to cowpea.

The relation of this virus to cowpea mosaic virus described by McLean and asparagus‐bean mosaic virus described by Snyder is discussed.
EXPERIMENTS WITH SOILS USED FOR CASING BEDS OF THE CULTIVATED MUSHROOM, PSALLIOTA CAMPESTRIS
Authors: PIZER N. H. , LEAVER W. E.
Published: February 2008

In the present paper an account is given of observations and experiments on the influence of the casing soil on the cropping of beds of the cultivated mushroom, Psalliota campestris. It is shown from the results of a survey of cropping at thirty‐nine mushroom farms that when the compost and cultural conditions are suitable for cropping, the production of mushrooms may be largely determined by the soil used for casing. Casing soils are classified into four grades depending on the numbers of sporophores formed, their rate of growth and the type of mushroom produced. A laboratory method of assessing the cropping potentialities of soils is described, and examples are given of its use for investigating field factors affecting the selection of soils for casing and the nature of the soil factors affecting cropping. It is suggested that chemical substances or specific surfaces in soils may promote cropping, but that close contact with air is necessary for them to be effective. It is concluded that direct trial is the only reliable method of assessing the value of a material for casing and that considerable fundamental research is needed on casing soils.