bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE SPREAD OF DISEASES CAUSED BY SPECIES OF VERTICILLIUM
Authors: ISAAC IVOR 
Published: February 2008

An investigation has been made of the spread of Verticillium disease of tomato and antirrhinum by root contact between diseased and healthy plants, and by the growth of the fungi through the soil. V. alboatrum and V. Dahliae spread rapidly by root contact, while V. tricorpus, V. nigrescens and V. nubilum showed no appreciable spread. Where the tomato and antirrhinum hosts wilted and died the causal organism was invariably isolated from the soil near the roots of the dead plants, but where the inoculated host harboured species without showing disease symptoms, as in the case of V. tricorpus and V. nubilum in antirrhinum, the parasite was never obtained from the soil. Moreover, these species in antirrhinum, and V. nigrescens and V. nubilum in tomato would appear to be mild pathogens since when they were already well established V. alboatrum was later actually found to enter and parasitize the respective hosts and bring about its own typical disease symptoms.Spread through the soil in the absence of hosts was tested by the insertion into it of infected wheat grains followed by later attempts to isolate the fungi at varying distances from the point of infection. V. alboatrum, V. Dahliae and V. tricorpus showed little or no growth through the soil, whereas V. nigrescens and V. nubilum spread saprophytically to some extent, though never attaining sufficient concentration to cause appreciable infection of later planted tomatoes.The conclusion is reached that spread of disease caused by species of Verticillium takes place mainly by root contact, with a rapidity relatively proportional to that of the death of the host. This finding, together with the lack of spread from antirrhinum plants infected with the non‐lethal V. tricorpus and V. nubilum, suggests that the parasites remain in the vascular tracts until the death of the hosts.
FUNGICIDAL ACTIVITY AND CHEMICAL CONSTITUTION
Authors: BYRDE R. J. W. , WOODCOCK D. 
Published: February 2008

2:3–Dichloro‐1:4‐naphthahydroquinone and several derivatives were prepared and tested in aqueous acetone solution against four fungi using a spore germination technique. The hydroquinone showed the same order of fungicidal activity as 2:3‐dichloro‐1: 4‐naphthaquinone, but was no less phytotoxic. Whilst the dibenzoyl ester and the dimethyl ether proved virtually inactive, the diacetyl ester was found to be as effective as 2:3‐dichloro‐1:4‐naphthaquinone against Sclerotinia laxa, Botrytis fabae and Cladosporium fulvum, and also less phytotoxic to plum fruitlets and tomato and broad bean foliage. Reduced fungicidal activity was shown when the substance was formulated as an aqueous suspension suitable for field application.The rates of alkaline hydrolysis of these esters have been determined, and a relationship between ease of hydrolysis and fungicidal activity is apparent. It is suggested that these compounds, whilst not inherently active, are similarly hydrolysed to 2:3‐dichloro‐1:4‐naphthahydroquinone in the presence of a fungal esterase.* Byrde, R. J. W., Crowdy, S. H. & Woodcock, D., ‘Studies on Systemic Fungicides. III’, Ann. appl. Biol. 40, 152, is regarded as Part I of this series.
THE EFFECTS OF VARYING THE WATER SUPPLY OF PLANTS ON THEIR SUSCEPTIBILITY TO INFECTION WITH VIRUSES
Authors: TINSLEY T. W. 
Published: February 2008

Increasing the amount of water supplied to plants before they were inoculated with viruses greatly increased their susceptibility to infection; plants that received unlimited water produced 10 or more times as many local lesions as plants that received only enough to prevent wilting. Susceptibility was increased throughout the year, but the full response occurred in 2 weeks in winter and 4 weeks in summer. Plants that received unlimited water for the 2 weeks immediately preceding inoculation were no more susceptible than those that received it during the previous 2 weeks, although the external appearance of the plants differed at the time of inoculation. Varying water supply after inoculation did not affect the numbers of lesions.The differences in susceptibility to infection produced by differential watering were decreased, but not abolished, by growing plants under shade or by incorporating a diatomaceous earth in the inoculum.Increasing water produced plants with larger and more succulent leaves; the cuticular layer was thinner, and the palisade tissue was less regularly arranged than in the plants kept dry. The increased susceptibility caused by an abundant water supply may be at least partly due to these structural differences, which allow the leaf to be damaged more easily when rubbed with inocula and so present more entry points for virus particles.
TRACE‐ELEMENT TOXICITIES IN OAT PLANTS
Authors: HUNTER JAMES G. , VERGNANO ORNELLA 
Published: February 2008

Excessive amounts of nickel, cobalt, chromium, copper, zinc, manganese, molybdenum and aluminium in nutrient solutions supplied to oat plants in sand culture produce (a) chlorosis and (b) other symptoms specific to the element involved. The specific symptoms are distinct for each metal, although those of cobalt and nickel might be confused.The toxic effects of nickel, cobalt, copper, zinc, manganese and molybdenum are associated with high concentrations of the element in the leaf tissue, but this is not always so with chromium and aluminium.The toxic effects of nickel, chromium, copper and molybdenum are associated with a reduced nitrogen content of the plant. Nickel, cobalt, chromium, zinc and manganese increase the concentration of phosphorus in the tissue whilst aluminium decreases it, probably to a deficiency level.Aluminium reduces the intensity of toxic symptoms produced by nickel—probably by reducing the uptake of nickel and phosphorus. Copper effectively reduces the leaf necrosis produced by nickel, but not the nickel content of the leaf tissue; it is suggested that one factor in nickel toxicity may be inhibition of one or more functions of copper. The other elements slightly increase chlorosis and some increase necrosis.The order of activitjl of the elements in producing chlorosis is found to be Ni>Cu>Co>Cr>Zn>Mo>Mn. This order, which is related to that giving yield reduction and is similar to the order of stability of metal complexes, is discussed in relation to induced iron deficiency.
COMPARATIVE PHYSIOLOGICAL STUDIES ON THE GROWTH OF FIELD CROPS
Authors: WATSON D. J. , WATSON MARION A. 
Published: February 2008

Infection with beet yellows virus depressed the dry‐matter yield of sugar‐beet plants by decreasing both leaf area and net assimilation rate (N.A.R.). It did not reduce the number of leaves.The lower N.A.R. of infected plants may occur because photosynthesis is slowed by chlorosis of the leaves or by changes associated with it. Plants infected at the end of June had 30‐50% of their leaf area yellowed from mid‐August. Later infection caused less yellowing. The yellowing almost sufficed to account for the decrease in N.A.R., if yellowed parts of leaves do not photosynthesize. However, the similar diurnal fluctuations of carbohydrate in the laminae of healthy and infected leaves suggests that photosynthesis may not be much slowed by infection; if so, the decrease in N.A.R. indicates a large increase in respiration rate, especially of the root.The effects of yellows on leaf area and N.A.R. appear to be independent; late‐sown plants suffered a greater reduction of leaf area, but a smaller reduction in N.A.R., than early‐sown plants; similarly treated plants showed the same reduction of leaf area in two successive years, but the decrease in N.A.R. was much greater in the second.Most of the loss of dry matter was in the root; the dry weight of the petiole (including stem tissue) was also decreased but the dry weight of leaf lamina was little affected.Yellows greatly increased the reducing sugars in the leaf lamina, and caused smaller increases in sucrose and starch. These effects appeared when the leaves showed only etch symptoms. The increase in starch was greatest at this time, but the effect on sugar content subsequently increased with the development of yellowing.Yellows reduced the water content, nitrogen content and the arealweight ratio of the leaf lamina. The change in nitrogen content, but not the others, could be accounted for by the rise in carbohydrate.Yellows had no effect on the water content of petiole and root; it increased the nitrogen content of these parts. It reduced the sucrose content of the root, but the loss of sugar yield was mainly attributable to decreased root weight.Infection with beet mosaic virus decreased the dry weight of sugar‐beet plants only when nitrogenous fertilizer was applied. As with yellows infection, the loss of dry matter resulted from reductions in both leaf area and N.A.R. Unlike yellows, mosaic depressed the dry weight of leaf lamina, as well as of petiole and root.Mosaic had no effect on carbohydrate content, water content or arealweight ratio of the leaf lamina, or on water content of petiole and root. It increased the nitrogen content of all parts of plants that received no nitrogenous fertilizer, but not of nitrogen‐treated plants. It slightly increased the sucrose content of the root.Infection with beet mosaic virus at the end of June caused a 20 yo loss of sugar yield from plants that received nitrogenous fertilizer. Yellows infection of similar plants at the same date reduced the sugar yield by 50%.
SYSTEMIC INSECTICIDAL ACTION OF NICOTINE AND CERTAIN OTHER ORGANIC BASES
Authors: DAVID W. A. L. , GARDINER B. O. C. 
Published: February 2008

Nicotine and nicotine salts are taken up by the roots of plants from solutions, and when 0.01–0.001 % nicotine is used the plants become toxic to Aphis fabae and to Pieris brassicae larvae and can be shown to contain nicotine. The results with Phaedon cochleariae adults and larvae are less satisfactory. No systemic action is observed when the nicotine is watered on to soil in which plants are growing and no nicotine can be detected in the plants. Apparently the nicotine is decomposed in the soil.When applied several times to the upper surface of a bean leaf nicotine kills aphids on the underside. There is some evidence that nicotine can be translocated further through the plant following leaf applications, but the toxic action at any distance is very weak in the plants used in the present experiments and can only be produced by frequent applications of rather concentrated nicotine solutions. Leaf absorption and subsequent translocation has not been observed with nicotine salts.The various organic bases, including some piperidine phosphonites and allied compounds tested, are of very little interest as contact or systemic insecticides against aphids.
BIOASSAY SYSTEMS FOR THE PYRETHRINS: V. EXPERIMENTS WITH A RESISTANT STRAIN OF CALANDRA GRANARIA L.
Authors: BLACKITH R. E. 
Published: February 2008

Some principles of testing for resistance in wild and laboratory stocks of insects are discussed, and experiments with Calandra granaria L. are described in which these insects are selected for pyrethrum resistance.A new method is described of expressing relative tolerances when the relevant regression lines are not parallel, based on the ‘generalized distance’ of Mahalanobis. The method may equally be used for the comparison of two insecticides giving rise to lines of different slope. A limited increase in resistance occurred on selection. Non‐random oscillatory sequences of slopes were observed when the resistant strain was assayed, and regression parameters computed. The nature of these oscillations is considered.
STUDIES ON BEETLES OF THE FAMILY PTINIDAE: VIII. THE INTRINSIC RATE OF INCREASE OF SOME PTINID BEETLES
Authors: HOWE R. W. 
Published: February 2008

The results of laboratory studies on nine species of warehouse Ptinid beetles at 25° C. and 70%r.h. are used to calculate by Leslie's methods, the statistic r measuring the intrinsic rate of increase of each species. Ptinus tectus Boield. has the highest value of r—0–38, equivalent to a 39 % weekly increase or tenfold in under 2 months. Four species, Gibbium psylloides (Czemp.), Mezium affine Boield., Stethomezium squamosum Hinton and Trigonogenius globulus Sol., are capable of tenfold increase in 3 months and the remaining four multiply more slowly, either because of a low oviposition rate (Eurostus), high developmental mortality (Niptus), or slow development (Ptinus fur (L.), P. sexpunctatus Panz.).Generally the intrinsic rate of increase falls with temperature due to lengthening of development and reduction of oviposition, but near the maximum of development it also falls because of high developmental mortality. Niptus has a higher rate of increase at 20° C. than at 25° C. which is close to its developmental maximum. Relative humidity has little effect except at the limits of humidity tolerance, but water must be occasionally available for the adult to drink, or oviposition and thus rate of increase is markedly depressed. Food mainly affects the rate of increase through its effect on developmental speed. Other factors are briefly considered.The statistic r applies to a population which has a stable age distribution. For Ptinids the stable age population was found by calculation to contain between 5 and 11% of adults, whereas in the warehouse never less than 15% of the population found were adults. In a warehouse actual observed rates of increase reached a value equivalent to r= 0.24 per week over a period of 8 weeks. From observed temperature means and laboratory results a maximum of r= 0.31 was predicted with a mean of 0.19 per week for a year. The value of r obtained using the oviposition rate estimated in the warehouse was 0.1. Warehouse values of r may be below those predicted from laboratory results because oviposition is restricted due to lack of drinking water and often to overcrowding, mortality increased due to disease, parasites, predators, and accidental cannibalism, and developmental speed retarded due to crowding.
THE RAPID DETERMINATION OF THE INTRINSIC RATE OF INCREASE OF AN INSECT POPULATION
Authors: HOWE R. W. 
Published: February 2008

The primitive (single oviposition period) method for determining the finite rate of natural increase (Λ) of an insect species which lays all its eggs quickly is described, together with a summary of a more accurate method introduced by P. H. Leslie and L, C. Birch of calculating the infinite (infinitesimal) rate of increase (r) of any species. The parameter r is the natural logarithm of the parameter Λ. Two methods of simplifying this more accurate method are discussed and illustrated by six examples which are used to compare the results given by all four methods.The first modification of the Leslie‐Birch method provides a means of representing a long oviposition cycle by a single figure so that the final calculation resembles the primitive single period method. The oviposition period is divided into a number of convenient unit periods, and using a table of weighting factors provided, the number of eggs laid in each of these unit periods is converted into the number of eggs required to be laid in the first of these unit periods of oviposition to make an equivalent contribution to the rate of increase. The equivalent oviposition figures for all the unit periods are summed to provide one figure which represents the observed egg number and pattern.The second modification provides a means of representing the observed egg pattern by a constant rate of oviposition. This requires the same table of weighting factors but also needs a series of charts which are provided. This method usually gives a good answer at the first attempt, whereas the first modification usually requires two trial and error solutions to give an accurate estimate of r and hence of Λ. Two of the examples show how the methods may be used for species for which information is scattered in the published literature. The minimum requirements for estimation of r are information on the length of the developmental cycle, the rate of egg output of adults, mortality of all stages and the sex ratio.
STUDIES ON SYSTEMIC FUNGICIDES
Authors: BYRDE R. J. W. , CROWDY S. H. , WOODCOCK D. 
Published: February 2008

A number of mono‐, di‐and trichloro‐β‐naphthols and the corresponding naphthyloxy‐n‐carboxylic acids were prepared. They were tested as systemic fungicides against chocolate spot of broad bean (Vicia faba) caused by Botrytis fabae and as fungicides in vitro by their effect on the germination of spores of Sclerotinia laxa and the growth of the mycelium of Botrytis fabae.The systemic fungicide tests showed no difference in the activity of the compounds associated with different side chains, though there were slight but significant effects associated with different chlorine substitutions in the naphthalene nucleus. The 3:4‐dichloro‐2‐naphthol derivatives were more effective than the other compounds tested.Fungicide tests with the 1:3‐dichloro‐2‐naphthol derivatives suggested that there was some increase in toxicity to the spores of Sclerotinia laxa with increasing length of side chain. The effectiveness of the various chlorine‐substituted compounds in suppressing growth of Botrytis fabae was in the following descending order, 1:3:4‐trichloro‐, 1:3‐dichloro‐, 1:4‐dichloro‐and 3:4‐dichloro‐compounds. The concentrations required in agar culture to induce reductions of B. fabae growth comparable to those found in the leaf could reasonably be expected to occur in the bean plants treated with the 2‐naphthyloxyacetic acids at 10 p.p.m.
BREEDING PEARS FOR RESISTANCE TO THE PEAR SCAB FUNGUS VENTURIA PIRINA ADERH.
Authors: STANTON W. R. 
Published: February 2008

Three clones of Venturia pirina have been tested for their pathogenicity towards forty varieties of cultivated pear. From observations on the reactions of these forty varieties, twelve were selected for differentiating the pathogenicity of sixteen clones of the fungus.These tests differentiated four main groups of biotypes of V. pirina. Clones isolated from Conference showed wide differences in range of pathogenicity. One isolate from Conference was shown to parasitize six of the most widely grown pears in England: other Conference biotypes had a narrow range.No variety of pear was found immune to all the isolates. Beurré Giffard was lightly infected by an isolate from Durondeau, but was resistant to all the other isolates tested.
OBSERVATIONS ON THE EFFECT OF GROWTH‐STIMULATING COMPOUNDS ON THE HEALING OF WOUNDS ON APPLE TREES
Authors: CROWDY S. H. 
Published: February 2008

Wounds were made at various times of the year on the trunks and large branches of apple trees with a 1 in. bit and treated with a number of organic compounds in lanoline paste. The healing of these wounds was followed through two growing seasons by tracing and measuring the area of exposed wood at different times after wounding.Callus growth was practically confined to the summer months. Development of callus was improved by applications of lanoline, and the lanoline effect could be further enhanced in the early part of the first growing season following treatment by the addition of certain growth‐stimulating compounds including 4‐chloro‐3:5‐dimethylphenoxyacetic acid and 2:4‐dichlorophenoxyacetic acid. Indolyl‐3‐butyric acid probably also caused some stimulation. After the period of initial stimulation the rate of callusing was approximately the same on treated as on untreated wounds.
THE SIGNIFICANCE OF THE LIGHT AND DARK PHASES IN THE PHOTOPERIODIC CONTROL OF DIAPAUSE IN METATETRANYCHUS ULMI KOCH
Authors: LEES A. D. 
Published: February 2008

The daily cycle of illumination is one of several agencies which control the onset of diapause in Metatetranychus ulmi. Both light and dark phases in the cycle are concerned in the determination process.In general, a long light phase tends to suppress and a long dark phase to induce a diapause. In any combination, the path of development is decided by the balance between diapause‐preventing (light phase) and diapause‐inducing (dark phase) stimuli. However, as their effectiveness does not increase linearly with duration, the existing balance changes with the phase duration.The effectiveness of the light phase in suppressing diapause increases most rapidly between 8 and 16 hr.; that of the dark phase rises very sharply between 8 and 12 hr. Longer dark periods of up to several days duration also induce diapause but are no more effective than a 13 hr. phase. The inclusion in the cycle of very long periods of light or darkness may also influence diapause by reducing the number of complementary phases experienced by the mite during the sensitive period of development. M. ulmi is highly insensitive to the interruption of effective light and dark phases by short intervals of darkness or light—a further indication of the slow inception of the light‐and dark‐phase reactions.These findings are discussed in terms of hypothetical mechanism involving cumulative synthesis and removal of some active substance, but the experimental results cannot yet be fully reconciled with a simple hypothesis of this kind.
THE MUTUAL EFFECT OF RYEGRASS AND CLOVER WHEN GROWN TOGETHER
Authors: MANN HAROLD H. , BARNES T. W. 
Published: February 2008

Italian ryegrass and a late‐flowering red clover were grown together, with abundance of water and nutrients for both. It was found that even a small number of ryegrass plants reduced the growth of clover by 30%. This effect varied very little with increasing density of the clover crop.The presence of clover reduced the ryegrass crop by an amount diminishing as the density of the ryegrass was increased. In a sparse crop of ryegrass, clover reduced the growth of the grass considerably more than did barley under comparable conditions.There is no evidence of any specific effect of the roots of one plant on the other. When ample nitrogen is available the clover tends to take some that would otherwise be available for the grass and does not provide the grass with additional nitrogen.
HOST ALTERNATION IN APHIS FABAE SCOP.
Authors: KENNEDY J. S. , BOOTH C. O. 
Published: February 2008

Experiments on the feeding preferences and relative fecundity of Aphis fabae among leaves of different ages and kinds were extended to the comparison of different forms of the aphid: apterous and alate virginoparae and gynoparae.All three forms showed a preference for the primary host, Euonymus, over a secondary host, sugar beet, but this preference was strongest in the gynoparae, weaker in the alate virginoparae and weakest in the apterae. The relative fecundity of the aphids on the two kinds of leaf paralleled their feeding preferences most closely in the gynoparae, less so in the alate virginoparae and least in the apterae.All three forms also showed some preference for growing over mature leaves of the same kind, but this preference was strongest in the apterous virginoparae, weaker in the alate virginoparae and weakest in the gynoparae. The relative fecundity of the aphids on the two ages of leaf paralleled their feeding preferences most closely in the apterae, less so in the alate virginoparae and least in the gynoparae.The physiological, ecological and evolutionary significance of the results is discussed in the light of the dual discrimination theory of aphid host selection.