bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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 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.
ANNONA SPECIES AS INSECTICIDES
Authors: HARPER S. H. , POTTER C. , GILLHAM (Mrs) E. M. 
Published: February 2008

By extraction and precipitation from several solvents the toxic principle present in Annona reticulata and A. squamosa seeds and roots has been concentrated up to one hundred‐fold. A preliminary chemical examination of this concentrate is described, leading to the conclusion that the toxicity is due to a glyceride or glycerides of a hydroxylated unsaturated acid or acids of high molecular weight.These extracts have been examined for contact and stomach poison and ovicidal properties in a variety of media. When used as a contact insecticide against Aphis fabae, Macrosiphoniella sanborni and Macronphum solanifolii, the concentrate exhibited a toxicity of the same order as that of rotenone, but against Oryzaephilus surinamensis the toxicity was considerably less. As a stomach poison the ether extract was both toxic and repellent to Plutella maculipennis larvae, but was neither toxic nor repellent to Diataraxia oleracea larvae. Ovicidal tests against the eggs of Plutella maculipennis and of Ephestia kühniella were inconclusive. The potency of this concentrate is therefore of a limited nature and although of roughly the same order as that of rotenone to certain aphides, it has neither the intensity of effect nor the range of insecticidal action of that compound.
THE COMPETITION BETWEEN BARLEY AND CERTAIN WEEDS UNDER CONTROLLED CONDITIONS: II. COMPETITION WITH HOLCUS MOLLIS
Authors: MANN HAROLD H. , BARNES T. W. 
Published: February 2008

The nature of the competition between barley and the twitch grass, Holcus mollis, has been studied. H. mollis has overrun much of the light, semi‐acid arable land near Woburn on Lower Greensand soils; about 2 1/2 tons of dry rhizomes and roots per acre were dug up on land where it had grown for 10 months. All this rhizome growth occurred within the top 8 in. of the soil. H. mollis commonly increases until the roots occupy from 0.11 to 0.141. root space per 1 g. dried roots and rhizomes. It is slightly superior to barley in ability to utilize available nitrogen.When barley and this Holcus are grown together with abundance of food and water for both plants, the effect of the weed on the yield of barley depends on whether the barley or the weed first becomes established and on the rate of sowing of the barley. If barley growth begins before that of Holcus, it may smother the weed completely and sustain no loss of yield provided the barley is planted thickly enough. If the two competing plants start at the same time, thickness of planting is still able to limit the extent to which the weed can reduce the yield of barley, though even with the thickest planting the Holcus can reduce barley yield by one‐third. Where Holcus is already established in the ground from the previous year and the crop is thinly planted, the weed is able to eliminate the barley completely, but where barley is sown thickly it is still able to give a 50% yield.With a sparse crop of barley, an increase in the number of weed units makes no difference to the growth of the barley provided the crop becomes well established. Where the crop and the weed start together and so compete on equal terms, any increase of Holcus growth is obtained at the cost of an almost equal falling off in the yield of barley, showing that the respective plant growths are almost complementary. Once the weed has fully occupied the soil, it is able to suppress the growth of the barley almost entirely. The barley and the Holcus reduce the growth of each other even when the root space and supply of plant food are ample for both.
EXPERIMENTS ON THE EFFECT OF CHLORINATED NITROBENZENES ON THE SPROUTING OF POTATO TUBERS
Authors: BROWN W. 
Published: February 2008

The addition of a small quantity of a dust containing pentachloronitrobenzene to clamps of certain early and second‐early potato varieties has a marked effect in reducing the amount of sprouting which takes place over winter and in protecting the sprouts from damage by the fungus Rhizoctonia Solani.A series of yield trials carried out over six seasons has shown that tubers which have been stored in clamps in presence of the dust give yields equal to those of chitted tubers.A dust containing a tetrachloronitrobenzene applied to potatoes kept in a closed space represses sprouting to a very pronounced degree. The possible use of this dust for conserving ware potatoes is suggested.