bluuebunny/crossref_metadata_2025_split huggingface dataset:
AN EXPERIMENT IN RABBIT CONTROL
Authors: PHILLIPS WINIFRED M. 
Published: February 2008

A successful experiment in rabbit control was carried out over one year on a 300‐acre farm in Pembrokeshire. The control measures adopted were trapping, gassing and ferreting, in that order. Information on rabbit density was based primarily on counts of rabbit holes and on the number of animals caught. Observations were made on the breeding state and sex ratio of the population. Successful control was attributed to the persistent application of a variety of methods, and not to any one method in particular. Gassing was equally efficient on high and low rabbit populations; the three methods of application, namely pumping, spooning and a combination of both, were found to be equally effective. Re‐infestation occurred, but was checked to some extent by trapping around the boundary.The breeding season appeared to extend from January to June, inclusive. The sex ratio was biased in favour of females throughout the experiment. An almost even sex ratio was observed in embryos.
THE EPIDEMIOLOGY AND CONTROL OF NOSEMA DISEASE OF THE HONEY‐BEE
Authors: BAILEY L. 
Published: February 2008

The proportion of honey‐bees infected with Nosema apis (Zander) declines in summer as the old infected bees die, for they cease to transmit their infection to the newly emerged individuals during the flying season. N. apis spores survive the summer on combs contaminated with infected faeces during the preceding winter. Although bees clean the combs during the summer, all infected material is not removed, and even well‐used brood comb, which has been repeatedly cleaned by bees, can carry infection. Only a few bees may contract infection in the autumn from these faeces, but they join the winter cluster and initiate the next outbreak of the disease. Transferring a colony on to clean comb early in the spring or summer removes the source of the disease, and it then disappears when all the old infected bees die.Old broodless comb can be sterilized quite simply by fumigation for a few days with the vapours of formalin or glacial acetic acid. Acetic acid is preferable, because it does not poison any honey or pollen in the combs. Formaldehyde can safely be used only with empty combs.The autumn is the best time for treating colonies chemotherapeutically, because the combs are then cleanest and the few bees which are infected can be cured during the winter. The drug can be incorporated in the syrup normally fed to colonies in autumn, and there is no risk of seriously contaminating subsequent honey crops. However, such treatment cannot eliminate the disease because sufficient spores remain on the combs for the disease to start again when the drug supplied in the winter stores is exhausted.
THE STANDARDIZATION OF AIR‐FLOW IN INSECT SUCTION TRAPS
Authors: TAYLOR L. R. , COLEMAN W. S. 
Published: February 2008

The air‐flow and its variations in sixteen insect suction traps of five different types have been measured, using regularity of air sample size as the criterion of efficiency. Traps with the air‐filtering cone enclosed in a cylinder and using axial flow fans with single‐phase capacitor‐start‐and‐run or three‐phase motors are most efficient and can have normal working limits of + 4 % of the mean air delivery.However, for smaller traps which are to be used only close to the ground or in cover, the original type with exposed cone and shaded‐pole motor is quite satisfactory provided certain precautions are taken. Normal working limits of 5 8 % are then obtained.These errors are derived in detail and the expected errors in more extreme conditions and with other traps are indicated.
THE APHICIDAL ACTION OF SOME SYSTEMIC INSECTICIDES APPLIED TO SEEDS
Authors: DAVID W. A. L. , GARDINER B. O. C. 
Published: February 2008

When large seeds such as broad bean are soaked in certain systemic insecticides, notably demeton, the plants which they produce are toxic to aphids. With small seeds the effect is difficult to detect.Experiments with demeton solutions and broad beans show that equal quantities of water and demeton are absorbed. Beans vary greatly in the rate at which they absorb solution, so, to reduce variations, about 24 hr. soaking is necessary. The insecticidal activity of the plant is directly related to the quantity of solution absorbed by the seed. Larger bean seeds absorb more solution than small beans and the plants are more toxic. After short periods of soaking (4 hr.) there is more insecticide in the seed coat than in the cotyledons, after 24 hr. there is more in the cotyledons. Some of the toxic material in the seed reaches the growing plant via the soil and roots. The material in the cotyledons can pass directly to the growing plant. As some of the material absorbed by the seed passes into the soil, any factors such as an increase in soil volume or heavy watering which tend to dilute the insecticides reduce the quantity of toxic material reaching the plant. The same quantity of demeton is more effective when absorbed by a seed than when watered on to the soil around it. Seeds soaked in insecticide, dried, and stored for one month produced plants toxic to aphids.
RELATIONSHIPS BETWEEN THE CHEMICAL CONSTITUTION AND FUMIGANT TOXICITY OF THE ALKYL IODIDES
Authors: HASSALL KENNETH A. 
Published: February 2008

Nineteen alkyl iodides have been tested as fumigants against the grain weevil, Calandragranaria, using the technique previously described. Relative toxicities, and also the toxicities of mixtures of selected pairs of iodides, were determined.Secondary and tertiary isomers were in general less toxic than the primary, irrespective of whether the toxicity was measured by molar LD 50' or the corresponding relative saturation (Pt/pB) values. Despite differences in LD 50', isomeric primary iodides often acted at about the samep,/p, value. It is suggested that these observations provide evidence that, although chemical reactivity appears to be the principal factor determining the values of LD so's in the iodide series, such physical factors as phase distribution also play their part, and their effect becomes noticeable for the primary isomers, for which the chemical reactivities may be nearly the same.The deaths of individual grain weevils which had been exposed to iodides were more or less delayed. The change of the kill with time was, under standard conditions, the same when all except methyl and the tertiary iodides were used, which suggests that with these possible exceptions, all the iodides have the same type of chemical action on the organisms. The toxicities of mixtures of selected iodides tended to confirm this, for they varied from about 1.0 to 1.25 times the value predicted from the toxicities of the single iodides using the similar action equation. Despite the apparent similarity in mode of action the LD 50's and pt / p8 values varied widely, as did the ratios of the LD 50's of successive homologues in different isomeric series. This suggests that neither the magnitude of the pt / p8 value, nor the way in which it changes from member to member in a series, gives always a useful indication of the type of action shown by a compound or group of compounds.
THE EFFECT OF REPEATED SPRAYING OF INSECTS ON THEIR RESISTANCE TO INSECTICIDES
Authors: TATTERSFIELD F. , KERRIDGE J. R. 
Published: February 2008

The administration of carbon dioxide in sublethal concentrations or for sublethal periods of time gave rise to an increased resistance to its effect in a strain of Drosophila melanogaster susceptible to the toxic effects of this gas. The effect did not appear to be permanent.The successive administration by spraying of sublethal concentrations of DDT and BHC did not increase the resistance of a strain of D. melunoguster to their effects, either in the insects sprayed or their progeny. Only when the dosages were such as to give a high death‐rate did a significant increase of resistance of the progeny of the treated insects take place; the tendency was if anything to increase susceptibility, although the indications were not in favour of DDT acting as acumulative poison.In a preliminan series of tests the topical application of D D T in sublethal doses to the adult insects resulted in a reduction in the amount or in the rate of egg laying.
A STUDY OF A FIELD POPULATION OF THE BLOWFLIES LU CILIA CAESAR (L.) AND L. SERICATA (MG.)
Authors: CRAGG J. B. , HOBART J. 
Published: February 2008

Attempts to measure the dispersion, population density and longevity of blowflies are described. The experiments were made at Aber, Caernarvonshire, in 1943 on a narrow strip of coastal farm land (if x f ml.). Two liberations of laboratory‐bred Lucilia sericata (Mg.) were made. On the second occasion 286 flies of each sex were marked, and nine males and nineteen females were captured, the last capture occurring 15 days after liberation. The population density of this species was estimated to be approximately seven males and sixteen females per acre for the 840‐acre strip on the day of the second liberation.On 24 days during the period 20 August–20 September 1943, field‐caught L. caesar (L.) females were marked, and trapping both by meat and chemical baits was continued for a further 3 weeks. 3600 females were marked, 847 being recaptured at least once, and sixteen on at least four occasions. In the later part of the blowfly season, a life of 5–6 weeks is apparently not unusual for L. caesar females. The population drawn upon by the traps at the liberation centre fluctuated between 700 and 30,000 during the 4‐week period. This may have represented a very localized concentration equivalent to 6–238 females per acre. Dispersion of marked L. caesar was low. On the assumption of a maximum spread of 5 miles, some 63 % of the marked flies remained within 4 mile of the liberation centre.
THE INFLUENCE OF HIGH CONCENTRATIONS OF AMMONIUM AND SODIUM MOLYBDATES ON FLAX, SOYBEAN AND PEAS GROWN IN NUTRIENT SOLUTIONS CONTAINING DEFICIENT OR EXCESS IRON
Authors: WARINGTON KATHERINE 
Published: February 2008

Ammonium molybdate supplying 20 or 40 p.p.m. Mo prevented chlorosis caused by low iron supply in young flax plants, but sodium molybdate was effective only at the higher concentration. Temporary darkening of the green colour of the shoots was also produced by 40 p.p.m. Mo in iron‐deficient soybean and pea plants, but was soon followed by more severe chlorosis. Symptoms of molybdenum toxicity always developed when 40 p.p.m. Mo were given, whether or not the intensity of chlorosis was reduced. With an increase in iron supply, a reduction in molybdenum toxicity symptoms was confirmed in soybean and peas. In flax the higher level of iron eventually proved excessive unless it was combined with 40 p.p.m. Mo. High molybdenum thus seemed able to counteract both iron deficiency and toxicity in this plant.High iron reduced the molybdenum content (p.p.m./d.m.) of both shoot and root in soybean, peas and also in flax provided the iron was not excessive. High molybdenum usually reduced the iron content of the shoot, but markedly increased it in the root. Molybdenum‐induced chlorosis could thus be partly attributed to inhibition in iron translocation, but the beneficial effect of high molybdenum or high iron on colour was not obviously correlated with the analytical data.
STUDIES ON THE EFFECT OF TEMPERATURE ON VIRUS MULTIPLICATION IN INOCULATED LEAVES
Authors: HARRISON B. D. 
Published: February 2008

The rate at which the Rothamsted tobacco necrosis virus (RTNV) accumulates in inoculated French bean leaves increases with rising temperature to 22°C. and then decreases. Three days after inoculation, leaves at 22°C. contain 4000 times as much virus as at 10°C. and 1000 times as much as at 30°C. At all temperatures the rate of accumulation may depend on the balance between synthesis and inactivation of RTNV, but inactivation becomes increasingly important with rise of temperature above 22° C. and as the virus content of the leaves increases. Above 22°C. the rate of multiplication may increase but less rapidly than the rate of inactivation, and exposing inoculated leaves to ultra‐violet radiation at various intervals after inoculation suggests that at 30°C. RTNV multiplies in and moves from the initially infected epidermal cells in slightly less than the 6 hr. needed at 22°C. Thirty hr. are needed at 10°C. Newly formed virus is rapidly inactivated at 30°C. Raising the ambient temperature also decreases the numbers of local lesions produced by RTNV, possibly by increasing the chances that the introduced virus particles will become inactivated. Increasing the virus content of the inoculum above the level giving one lesion per sq.cm. does not increase the subsequent virus content of inoculated leaves.At temperatures of 30°C. and below, tomato aucuba mosaic virus produces necrotic lesions in leaves of tobacco and Nicotiana glutinosa whereas above 30°C. the lesions are chlorotic. In both hosts this virus multiplies more rapidly when the infected cells are killed.
SOME OBSERVATIONS ON THE HATCHING RESPONSES OF THE CABBAGE‐ROOT EELWORM, HETERODERA CRUCIFERAE FRANKLIN
Authors: DONCASTER C. C. 
Published: February 2008

Samples of root diffusate from sprouts (Brassica oleracea var. gemmifera), swedes (B. napus var. napobrassica), rape kale (B. napus var. arvmsis), and white mustard (Sinupis alba), all stimulated larval emergence from cysts of Heterodera cruciferae. When mustard‐root diffusate was added to leachings from the other species tested there was no apparent effect on larval emergence. In half dilution with tap water, mustard leachings were comparable in activity with similar dilutions of leachings from the other species under observation. Leachings from soil were less active than those from the four species of plants tested, but showed significant activity in comparison with tap water.The form of the hatching curve was studied using diffusates from both sprouts and mustard roots, and in each case when cumulative hatch was plotted against time on a logarithmic scale, the sigmoid curve obtained closely fitted the theoretical sigmoid calculated from a probit analysis of the data.Estimates were obtained of the log activity values of leachings from the four species of plants tested and from soil, following an examination of the dilution curves for mustard and sprouts root diffusates. These curves were closely parallel with one another, and it was therefore considered justifiable to derive log activity values for these root diffusates, although the cysts used in the hatching tests and the root‐diffusate samples were each obtained from a single source. For this reason some caution is perhaps called for in the interpretation of the results presented in this paper.
PECTIC ENZYMES SECRETED BY VERTICILLIUM DAHLIAE AND THEIR ROLE IN THE DEVELOPMENT OF THE WILT DISEASE OF COTTON
Authors: KAMAL M. , WOOD R. K. S. 
Published: February 2008

An isolate of Verticillium dahliae obtained from Uganda was highly virulent to young cotton plants under greenhouse conditions. A hyaline variant which often appeared in culture was as virulent as the parent isolate, but preliminary experiments indicated that it did not survive as long in unsterile soil. The parent isolate grew rapidly in cotton plants after root inoculation and was isolated from stems and leaves well before the appearance of disease symptoms visible to the naked eye.Protopectinase was produced in the absence of pectic materials, but more active preparations were obtained when media contained pectic substances. In general, there was a close correspondence between the protopectinase activity of culture filtrates and the toxicity of these filtrates to parenchymatous cells. Some separation of the two activities was obtained by heating enzyme solutions or by plasmolysing the test tissue.Protopectinase solutions had little pectinesterase activity but rapidly reduced the viscosity of solutions of pectic substances. In general, the properties of protopectinase and the viscosity‐reducing enzyme were similar.Young cotton shoots wilted rapidly when placed in cell‐free filtrates from cultures of the pathogen. Wilting was delayed under conditions unfavourable for transpiration. Evidence was obtained which showed that wilting was caused by the uptake of thermostable compounds of high molecular weight which impeded the upward flow of the vascular sap. Pronounced vascular browning was obtained only when solutions containing protopectinase were used. Wilting and vascular browning were obtained with solutions having little pectinesterase activity; in contrast, a solution having high pectinesterase activity produced relatively little vascular browning.
AN ANALYSIS OF THE EFFECTS OF INFECTION WITH LEAF‐ROLL VIRUS ON THE GROWTH AND YIELD OF POTATO PLANTS, AND OF ITS INTERACTIONS WITH NUTRIENT SUPPLY AND SHADING
Authors: WATSON D. J. , WILSON J. H. 
Published: February 2008

The decrease in total dry weight of potato plants (var. Craig's Defiance) caused by infection with leaf‐roll virus was almost entirely at the expense of the tubers; the dry weight of the leaves and stems was increased, and that of roots and stolons only slightly decreased. The percentage loss of dry weight of the tubers was decreased by nitrogenous fertilizer, but was unaffected by phosphorus or potassium.Infection greatly decreased net assimilation rate (NAR) between May and early July, but subsequently infected plants had a higher NAR than healthy plants. Infection also decreased leaf area per plant until early July, but it delayed senescence of the leaves, so that in late July and August infected plants had more leaf area than healthy plants. The more rapid senescence of healthy plants probably accounts for their lower NAR at this time. The mean decrease in NAR by infection was about 20%, and this was the chief cause of the loss of yield, for the mean decrease in leaf area was only 4%.Comparisons of intact plants with plants from which either the rolled or the unrolled leaves were removed indicated that the lower NAR of infected plants was mainly due to diminished photosynthetic efficiency of the older, rolled leaves. The effects of nitrogen, phosphorus and potassium on NAR, and their interactions with infection, were small and rarely significant.Nitrogenous fertilizer increased leaf area throughout the growth period; phosphorous increased it in the early stages but hastened senescence of the leaves, so that in August it decreased leaf area; potassium increased leaf area particularly in the later stages of growth. At the times when nitrogen, phosphorus or potassium increased leaf area they usually also increased the effect of infection as this tended to reflect plant size. Except in the early stages of growth infected plants had more leaves than healthy plants, because leaf production continued longer and more lateral branches developed.Shading decreased NAR but increased leaf area; consequently it had no effect on yield. There were no interactions between shading and infection.The loss of yield caused by infection of Up‐to‐Date plants was smaller than with Craig's Defiance because the leaf area of Up‐to‐Date was not decreased by infection, and the depression of NAR started later than with Craig's Defiance.
A LOCAL‐LESION TECHNIQUE FOR MEASURING THE INFECTIVITY OF CONIDIA OF BOTRYTIS FABAE SARDIÑA
Authors: LAST F. T. , HAMLEY ROSEMARY E. 
Published: February 2008

Discrete lesions developed when conidial suspensions of Botrytis fabae Sardiña were rubbed with the forefinger on leaves of broad bean plants (Vicia faba L.) subsequently kept in a water‐saturated atmosphere. The numbers of lesions which developed were directly proportional to the concentration of inoculum. At equal concentrations, conidia from young cultures produced more lesions than conidia from old cultures.Variation in lesion numbers between plants within a pot always considerably exceeded the variation between opposite half‐leaflets of a leaf, as did variation between pots and between leaves of old, but not of young plants.As the standard error of the number of lesions developing per half‐leaflet (x) increases as the mean increases, the values of x need to be transformed before being statistically analysed. A suitable transformation isz = log10 1/2{x + c +√(x2+ 2cx)}, where c = 20.
BROWN ROOT ROT OF TOMATOES
Authors: EBBEN M. H. , WILLIAMS P. H. 
Published: February 2008

Tomato roots with brown root rot showed three types of lesion: cortical rot of fine roots, ‘corky root’, and basal stem rot. The fungi most commonly isocated from diseased roots were: Colletotrichum atramentarium, Chaetomium spp., Cephalosporium spp., Volutella ciliata, and a grey mycelial fungus sometimes producing pycnidia (Pyrenochaeta sp.). Other fungi isocated less frequently were: Myrothecium roridum, Petriella asymmetrica, Trichoderma airide, Phytophthora spp., Alternaria sp. and Fusarium spp. There were differences between the numbers of each species isocated from the three types of lesion in steamed and in unsteamed soils, and some seasonal variation.Inoculation experiments with seedlings in vitro showed that Ckaetomium cochliodes and Petriella asymmetrica could infect radicles. On older plants growing in soil Colletotrichum atramentarium was the only effective pathogen. Culture filtrates from C. atramentarium, Chaetomium cochliodes, and P. asymmetrica decreased root growth when tested in vitro. Leachates from loam and a loam‐manure mixture decreased the growth of tomato root‐tip cultures; the effect of these leachates was altered by autoclaving.
THE PRODUCTION OF ANTIBIOTICS IN SOIL
Authors: WRIGHT JOYCE M. 
Published: February 2008

Antibiotic production in and around particles of plant debris in soil was studied. High yields of an antibiotic, shown by bioassay methods to be similar to gliotoxin, were obtained from wheat straws buried in a normal, unautoclaved; acid podsoc from Wareham Heath which had been inoculated with a strain of Trichoderma viride known to produce gliotoxin in culture media. Only a little of the antibiotic was produced in the soil immediately surrounding the straws. Much less was produced in straws buried in John Innes potting compost and none at all in straws buried in a Kettering loam. In no case was an antibiotic detected in straws from un‐inoculated soils.If, however, the Kettering loam was acidified or, alternatively, the straws themselves were acidified and then buried in untreated Kettering loam, good yields of the antibiotic were obtained from straw extracts. Conversely, when the pH of Wareham Heath soil was raised by addition of calcium hydroxide to the soil no antibiotic activity could be detected in the straws. This suggests that the pH of the soil and of the food substrate has a profound effect on production of an antibiotic, assumed to be gliotoxin, by T. viride. The results obtained suggested that increased production of gliotoxin after autoclaving the straws was due to a decrease in the pH of the straws rather than to a release of nutrients.