bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on the dispersion of Lycopodium and Podaxis spores in the air
Authors: SREERAMULU T. , RAMALINGAM A.
Published: February 2008

In twelve experiments known quantities of Lycopodium spores (in five with spores of Podaxis) were liberated into the open air artificially from a point source, under different meteorological conditions, and trapped on ‘Vaseline’‐coated slides, placed horizontally at: 2.5, 5.0, 10.0, 15.0, 20.0, 25.0 and 30.0 m. from the source, along from five to thirteen radii (20° apart in some experiments, and 5° or 10° apart in others).

The size of spore had little effect on the relative numbers of Lycopodium and Podaxis spores deposited at different distances (the deposition gradient), but from a cloud containing ten times as many Podaxis as Lycopodium spores over twice as many Lycopodium were deposited per unit area as were Podaxis spores. The rate of deposition is thus approximately proportional to the volume of the individual spore.

Estimated percentage recovery, within the sampling area, of Lycopodium spores liberated varied from 5.4% (afternoon in wind of 4.4 m./sec.) to 91.6% (night in wind of 0.8 m./sec). Recovery of Podaxis varied from 0.3 % by day to 1.6% by night.

The results of these experiments are examined in the light of the statistical theories of W. Schmidt and O. G. Sutton, which formulate atmospheric diffusion by eddies, and are found to be in closer agreement with the latter. The values of the parameters ‘m’ in Sutton's equation agree excellently with his theoretical values, but the values of the parameter ‘C’ are more variable.
Wilt of lucerne caused by species of Verticillium
Authors: ISAAC IVOR , HEALE J. B.
Published: February 2008

Resting mycelium of V. albo‐atrum in moribund lucerne remains viable at room temperature for 13 months but is not viable after 2 years, whereas conidia on lucerne seed kept at room temperature fail to germinate after 7 months.

The fungicide, Orthocide (captan) is toxic both to the conidia of V. albo‐atrum on seed coats of lucerne and to infected plant material carried with seed. Dressed seeds inoculated with Rhizobium mellelotus developed into healthy seedlings bearing normal root nodules, although the Orthocide is toxic to the bacterium in culture.

Dressing of seeds with Orthocide, Agrosan‐GN (containing mercury) and Fernasan (thiram) after inoculation gives slightly higher yields of lucerne than where dressing is done before inoculation, but this is not sufficient to recommend a change in the normal commercial procedure of dressing before inoculation.

Methyl bromide, used commercially as a fumigant to control Ditylenchus dipsaci, has no effect on Verticillium. However, allyl alcohol, allyl bromide, chloropicrin and formaldehyde are shown to be useful fumigants to control Verticillium carried with seed, since at exposures which kill the resting mycelium and conidia of V. albo‐atrum, they do not affect the viability of lucerne seed.
The effect of vernalization on embryos of field‐resistant wheat varieties infected by loose smut (Ustilago tritici)
Authors: MANTLE P. G.
Published: February 2008

The occurrence of an incompatible host/parasite reaction between winter wheat varieties infected with three Cambridge loose smut races was observed following vernalization of inoculated seed. This led to a re‐investigation of certain embryo‐susceptible field‐resistant combinations and the incompatibility reaction was found to be usual. Other unusual reactions were also observed. Whereas it was previously thought that loose smut mycelium failed to penetrate the plumular bud of embryo‐susceptible field‐resistant wheat varieties, it is shown that in fact the plumular bud may be infected with a subsequent serious effect on the host's development. Consequently a modified scheme for determining varietal reaction to loose smut infection is suggested.
Investigations on fungicides
Authors: BATES ANGELA N. , SPENCER D.M. , WAIN R.L.
Published: February 2008

The in vitro fungicidal activity of 2‐methyl‐4,6‐dinitrophenol (DNC) and fifteen of its esters was determined in mycelial growth tests. The aliphatic esters possessed similar activity to that of DNC and the aromatic esters were much less fungitoxic. The benzoic ester was only weakly active against mycelial growth and in preventing spore germination but as a protectant fungicide in vivo it was very effective. It was established that DNC‐benzoate is stable in light, under conditions of high humidity and in the presence of fungal spores, but it was shown that some degree of hydrolysis occurs on the leaves of broad bean to yield the parent cresol. This hydrolysis does not lead to phytotoxicity but the small quantities of DNC produced could account for the protectant fungicidal activity of this compound.
Studies of the fungitoxicity of captan
Authors: RICHMOND D.V. , SOMERS E.
Published: February 2008

A study has been made of the factors controlling the uptake of captan from aqueous solution by conidia of Neurospora crassa. The uptake process has been found to deviate from normal diffusion in the effects of captan concentration, temperature, salts, oxygen supply, and metabolic poisons. It is suggested that the captan absorbed by the spores is decomposed on or within the cell protoplast by a process requiring cell metabolic energy. Pre‐treatment of the spores with thiol reagents such as iodoacetic acid and p‐chloromercuribenzoate markedly decreased the uptake of captan without affecting spore viability or captan toxicity. This suggests that much of the high level of captan uptake required to inhibit spore germination is in fact being decomposed by cell thiols before reaching its site of toxic action.
Studies on the chemical control of Phytophthora palmivora (Butl.) Butl. on Theobroma cacao L. in Nigeria
Authors: Hislop E.C. , Park P.O.
Published: February 2008

A technique is described whereby detached cocoa pods can be inoculated with zoospores of Phytophthora palmivora to produce multiple lesions. The number of lesions developing can be correlated with the concentration and efficiency of protectant fungicides applied to the pod before inoculation. A number of fungicides have been tested by this method and the results are in general agreement with those obtained from field trials.
Studies on the chemical control of Phytophthora palmivora (Butl.) Butl. on Theobroma cacao L. in Nigeria
Authors: Hislop E.C. , Park P. O.
Published: February 2008

Two field trials of fungicides for the control of Phytophthora palmivora on cocoa in Nigeria are described. The results obtained during two harvest periods have been subjected to two methods of analysis and are compared and discussed. The field results have been correlated with the results of laboratory bio‐assays and a close agreement is demonstrated. Possible reasons for the poor control of P. palmivora in the field trials are considered in the light of results obtained from laboratory tests of fungicides (Hislop & Park, 1962a, b).
Dry‐rot disease of the potato
Authors: McKEE R.K. , BOYD A.E.W.
Published: February 2008

The effect of diphenyl on potato dry‐rot infection was investigated in laboratory tests and field trials. Diphenyl reduced infection in the laboratory but failed to give consistent control in the field, where such treatments as were effective also proved phytotoxic. Treated tubers were also tainted.
Physiologic races of Phytophthora fragariae
Authors: HICKMAN C.J.
Published: February 2008

Pathogenicity tests with forty‐nine isolates of Phytophthora fragariae, cause of red core disease of strawberry, using the strawberry varieties Huxley, Perle de Prague, Climax, Talisman, Aberdeen and Cambridge Vigour, revealed the existence of twelve physiological races of the fungus on the basis of a pathogenic or non‐pathogenic reaction. Further differentiation, on the basis of degree of pathogenicity to Perle de Prague and to Climax, allowed the recognition of nineteen races.

Varying the concentration of zoospores used as inoculum, and the length of inoculation period, which did not affect the relative pathogenicities of two isolates tested, had greater effects on the level of invasion with a highly pathogenic isolate than with a slightly pathogenic one.

Amongst the isolates differences uncorrelated with other characters such as pathogenicity were demonstrated in growth characters in agar culture and in abundance of zoospore production.
Biological activity of bulbiformin in soil
Authors: VASUDEVA R.S. , SINGH G.P. , IYENGAR M.R.S.
Published: February 2008

Bacillus subtilis is capable of producing the antibiotic bulbiformin in soil. Antibiotic production is considerably enhanced when the soil is sterile and enriched with nutrients such as aspartic acid or asparagin, and dextrose or certain root residues. In the presence of the root supplements the antibiotic persists in soil over several weeks in fairly high concentrations.

Under favourable conditions for antibiotic production such as the presence of root residues, inoculation of B. subtilis into soil results in a marked lowering of the incidence of pigeon‐pea wilt due to Fusarium udum.
The effect of growing resistant potatoes on a potato‐root eelworm population—a microplot experiment
Authors: COLE C.S. , HOWARD H.W.
Published: February 2008

The effect of growing resistant potatoes bred from Solanum tuberosum subsp. andigena and of non‐host crops on a potato‐root eelworm, Heterodera rostochiensis, population was studied for 4 years in microplots of a sandy loam. The reduction in the egg population from growing resistant potatoes was about 80% per year, a higher value than had been obtained previously for a black fen soil but agreeing with Dutch and German results. After 4 years of resistant potatoes the egg population was only about 1% of the initial value, and no increase in the frequency of ‘resistance‐breaking’ (biotype B) eelworms was detectable. Reductions in the egg populations from growing non‐host crops were about 60% in the first year but very much smaller in the second to fourth years. After 4 years of non‐host crops the egg population was still about 25% of the initial value.
Further studies on the host range and properties of Trinidad cowpea mosaic virus
Authors: CHANT S.R.
Published: February 2008

Additional to previously recorded host reactions, Trinidad cowpea mosaic caused local lesions in French bean (Phaseolus vulgaris L.), Bengal bean (Mucuna aterrima, Holland), Petunia hybrida Vilm. and Chenopodium amaranticolor Coste & Reyn; the last two are the only known non‐leguminous hosts. C. amaranticolor and French bean were used to study some properties of the virus. Infectivity was not affected by exposure to pH values between 5 and 9.1, to a 50% saturated solution of ammonium sulphate or a 50% solution of acetone or ethyl alcohol. The virus has polyhedral particles with a mean diameter of 25 mμ (approx.).
Alternate hosts of cucumber powdery mildew
Authors: STONE OLWEN M.
Published: February 2008

Cucumber powdery mildew is a common obligate parasite of glasshouse cucurbit crops in Britain. In the Cucurbitaceae only the genus Luffa was immune to infection. The fungus cannot survive the winter on cucurbits, but may persist on alternate hosts. Several common weeds were susceptible to experimental infection by the fungus and Sonchus asper is a very probable source of re‐infection for cucurbits. Chrysanthemum powdery mildew would not infect cucurbits, nor would the cucurbit mildew infect chrysanthemums.
Studies on strawberry mildew, caused by Sphaerotheca macularis (Wallr. ex Fries) Jaczewski*
Authors: PERIES O.S.
Published: February 2008

The development of S. macularis from spore germination to sporulation is described.

Two Fragaria species and thirty‐six varieties of cultivated strawberries were tested for foliar reaction to mildew infection. Both F. chiloensis (originally from Ecuador) and F. ovalis were extremely susceptible. In the cultivated varieties tested, leaves of Cambridge Favourite, Huxley and Late Pine were found to be the most resistant. There were no immune varieties.

Tests with isolates of the fungus from different parts of the country gave no evidence for the existence of physiologic races.

The effects of certain leaf‐surface fractions on conidial germination have been demonstrated and their significance discussed.

Histological studies have shown that leaf resistance is correlated with the relative difficulty of penetration of the cuticle and epidermal wall by the fungus. Necrotic symptoms appearing in leaves of certain varieties of strawberries on infection had no bearing on host resistance.
Overwintering of hop downy mildew Pseudoperonospora humuli (Miy. and Tak.) Wilson
Authors: COLEY‐SMITH J.R.
Published: February 2008

The experiments described in this paper show that Pseudoperonospora humuli can overwinter in infected hop rootstocks in the form of mycelium and that primary infected shoots (basal spikes) are produced from dormant buds infected by such mycelium. Crop yield from plants with infected rootstocks averaged 27.7% less than that from healthy plants.
Root exudates from banana and their relationship to strains of the Fusarium causing Panama wilt
Authors: BUXTON E.W.
Published: February 2008

A method is described for obtaining sterile exudates from banana roots still attached to the parent plant. Root exudates from the varieties Gros Michel (susceptible to Panama wilt) and Lacatan (resistant) were tested for their effects on spore germination of three strains of the pathogen, Fusarium oxysporum f. cubense.

In a medium otherwise optimal for spore germination, root exudates from 3–6‐month‐old Lacatan plants inhibited spore germination whereas root exudates from Gros Michel did not. The extent of the inhibition depended on the strain of the Fusarium tested and it decreased with ageing of the plants from which the root exudates came. In weak sucrose or soil‐extract media, root exudates from Gros Michel promoted spore germination of each strain. Exudates from young Lacatan plants did not promote germination in these two media, but exudates from 7–9‐month‐old did, although less than Gros Michel exudates.

Chromatograms showed eighteen amino acids in the root exudates, thirteen common to both banana varieties. Gros Michel root exudates contained no detectable cystine or threonine, and Lacatan no leucine, serine or tyrosine. Root exudates from young Lacatan contained more aspartic acid, glutamine and proline than those from young Gros Michel, but the differences decreased as the plants aged.

Total carbohydrates were maximal in root exudates from 6‐month‐old plants of both varieties. Gros Michel had 1.5 times more carbohydrate than Lacatan when young, but plants 3 and 9 months old contained almost equal amounts. Chromatograms showed that eight sugars were present and Gros Michel exudates had more of each sugar than did Lacatan at all stages of sampling.

Materials that inhibited spore germination on Dox‐agar media were demonstrated at RF 0.7 on chromatograms of Lacatan exudates. Neither ninhydrin‐reactive spots nor spots that fluoresced under ultra‐violet light occurred at RF 0.7 with Gros Michel exudates; nor did any materials at that RF inhibit spore germination.

The relationships between materials in the root exudates from the wilt‐susceptible and wilt‐resistant plants and differences in spore germination responses are considered as part of a wilt‐resistance mechanism in the rhizosphere of banana.
The effects of temperature and relative humidity on mortality in Limothrips cerealium Haliday (Thysanoptera) overwintering in bark
Authors: LEWIS T.
Published: February 2008

The temperature, relative humidity and pressure changes in the bark of Austrian pine during the winter 1960/61 are described. The lowest temperatures occurred in December and January, and the highest mostly in March and April. There was a large diurnal temperature range of up to 34° C. on sunny days, which was usually greatest on the eastern side of the trunk. The relative humidity of air in bark crevices on the sunny side of the tree often fell below 30%: it increased to over 80% at night and in wet weather. In dull weather the temperature and relative humidity fluctuations were less. Changes of temperature and humidity produced contractions and expansions of up to 0.006 in. in the radial thickness of the bark.

The susceptibility of L. cerealium to low temperatures was not affected by the acclimatization temperature within the range tested. Thrips were tolerant of continuous chilling and rapid fluctuations in temperature far more severe than conditions experienced in the field, providing that humidity was high. Prolonged artificial chilling caused muscular incoordination and eventually death. Activity ceased between 0° and 5° C. There was a suggestion, which was not satisfactorily proved, that cold hardiness increased slightly from October to March, but frost is unlikely to cause much mortality during the winter.

Thrips died quickly in warm, dry air and such conditions in the bark in spring, when emergence is starting, are probably the most important cause of the small amount of mortality which occurs. In these conditions the bark contracts and thrips may be crushed or perhaps trapped and subsequently desiccated by the sun.
Studies of earthworm populations in orchards
Authors: RAW F.
Published: February 2008

The amount of leaf litter buried by worms between leaf fall and spring was measured in two stages in five grass and two arable orchards near Wisbech, Cambs. A known number of weighed leaves was placed on the ground beneath wire cages at leaf fall and again several weeks later and those remaining at the end of each stage were counted and weighed. Unburied leaves lost about one‐quarter of their dry weight during each stage. Buried leaves were pulled into burrows by Lumbricus terrestris (Linn.), apparently the only species present that did so. Populations of L. terrestris beneath the cages were estimated from the number brought to the surface by dilute formalin.

In grass orchards, the number and weight of leaves buried was closely correlated with the estimated fresh weight of L. terrestris. Some orchards had 3/4 to 1 ton of L. terrestris per acre and in these over 90% of the normal leaf fall (1/2 ton dry weight) was buried during winter. Earthworm activity could account for the observed amounts of leaf litter removed in winter and observed differences between orchards could be attributed to differences in their L. terrestris population.

Apple leaves were buried more rapidly in arable than in grassed orchards, probably because they were the only ones and were easier to find and bury when there was no grass. Evidence to support this came from one grass orchard where the number of leaves buried from each cage was inversely proportional to the amount of surface vegetation. Twice as many leaves were buried in cages initially containing 200 leaves as in cages containing 100 leaves.

The rate at which L. terrestris buried leaves depended on soil temperature, and burial probably stops at 2° C, which is about 1.6° C. below the lowest weekly average temperature reached in Wisbech soils in winter.

The long‐term effect of leaf burial was shown by the contrasting soil profiles of a typical grass orchard and one where L. terrestris is rare, where the crumb structure is poor and where the accumulated remains of up to 15 years leaf fall now form a surface mat 1/2 ‐1 1/2 in. thick.
The epidemiology of tomato mosaic
Authors: BROADBENT L.
Published: February 2008

A type of ‘White Burley’ tobacco distinguished between the strains of tobacco mosaic virus (TMV) present in sixty out of sixty‐four smoking tobaccos and in 187 out of 203 British tomato crops and tests with it suggest that smoking tobacco is seldom a source of virus for tomato crops. A tobacco strain was found on one nursery only, in some grafted plants. Cucumber mosaic virus occurred in one and potato virus X in thirteen crops. Tomato plants were not readily infected when handled after handling infected dry tobacco, though they were usually infected when rubbed with water extracts. Infection with tomato strains of TMV usually, but not always, protected tomatoes against infection with the tobacco strain.
Some effects of far‐red irradiation and gibberellic acid on the growth of tomato plants
Authors: SELMAN I.W. , AHMED E.O.S.
Published: February 2008

The effects of supplementary irradiation with a far‐red (FR)‐rich source on tomato plants raised in a growth room with warm‐white fluorescent tubes as the FR‐deficient, primary light source have been studied with and without the application of gibberellic acid (GA).

Stem elongation in response to FR was independent of the amount of GA applied. Small but significant increases in fresh weight of leaflet laminae were sometimes obtained with GA. The optimal dose was about one‐eighth of the saturation dose for stem height. By combining the optimal daily GA dose for fresh weight laminae with FR, significant increases were obtained for fresh and dry weights of laminae and for stems plus petioles. The increase in lamina dry weight and leaf area amounted to 55 and 54%, respectively, with 15 days of treatment.

It was concluded that GA and FR affect growth in distinct ways. FR may release a growth factor in both leaves and stems and GA probably substitutes for native gibberellins in stems.
The effects of cathode ray irradiation of wheat on surface moulds, respiration, flour flavour and odour, and germination
Authors: CROPSEY M.G. , LEACH C.M. , CHING TE MAY , SATHER LOIS A. , WIANT D.E.
Published: February 2008

The effects of cathode ray radiation on the respiration, germination, flavour and odour, and microflora of stored wheat were determined by irradiating kernels at different moisture levels, under different combinations of dosage (10,600‐2,000,000 rep) and of voltage (600,000–1,000,000 V.) and on one side or two sides.

The lethal effects of irradiation on the natural microflora of kernels, and on the spores of Penicillium corymbiferum artificially inoculated onto kernels, were determined in preliminary experiments. Extensive studies with kernels artificially inoculated with Aspergillus repens, a proven storage mould, showed that as dosage was increased there was a corresponding reduction of viable spore load, with some reduction even at the lowest dosage of 10,600 rep. Irradiation of kernels at the highest applied voltage of 1,000,000 was more effective in killing spores than at 600,000; also a dosage applied on two sides was more effective than an equal dosage applied on one side. Spores were more readily killed when kernels were irradiated at a higher moisture level.

Dosages above 42,400 rep (total dosage at 600,000 V.) significantly reduced the total number of normal plants germinating from irradiated kernels whether radiation was applied on one or both sides, or at high or low moisture levels. At 23,000 rep (total dosage at 1,000,000 V.) the number of normal plants produced from germinated kernels was significantly reduced, whether radiation was applied on one or both sides, or to kernels held at high or low moisture levels.

The thresholds for irradiated flavour and odour for flour milled from irradiated kernels were about 169,600 rep (total dosage at 600,000 V.) and about 46,000 rep (total dosage at 1,000,000 V.), regardless of the moisture content or whether the dosage was applied on one or both sides. There was a significant reduction of the respiration of high moisture wheat inoculated with Aspergillus repens, when irradiated at dosages greater than 11,500 rep (total dosage at 1,000,000 V.), whether radiation was applied on one or both sides. Likewise, there was a significant reduction in respiration of kernels irradiated at dosages of 19,500 rep (total dosage at 600,000 V.), whether this was applied to one or both sides. The respiration of high moisture kernels was not reduced to that of the low moisture kernels until the 500,000 rep dosage.
The ecology of nematode‐trapping fungi in the soil
Authors: COOKE RODERIC C.
Published: February 2008

The decomposition of sucrose in non‐sterile soil stimulates an increase in both the population of free‐living nematodes and the activity of indigenous nematode‐trapping fungi. After sucrose decomposition reaches a certain stage the fungi cease to trap the nematodes still present in the soil. Increasing the amount of sucrose added to the soil stimulates greater increases in nematode population but results in a decrease in predacious activity of the fungi. Experiments using nematode‐free soil suggest that the presence of nematodes is necessary to initiate the formation of trapping organs, but that the fungi are incapable of remaining in a predaciously active state in the absence of an organic energy source other than the nematodes. The significance of this is discussed.
An approach to the chemotherapy of silver leaf disease (Stereum purpureum (Fr.) Fr.) of plum trees*
Authors: BENNETT MARGERY
Published: February 2008

Three‐ or 4‐year‐old plum trees of the varieties Victoria and Purple Pershore, infected in the trunk with spore suspensions during the autumn, proved suitable for testing the effects of chemicals injected in the attempt to cure silver leaf disease (Stereum purpureum) and provided material for the assessment of the effects over more than one season.

Indications were found that the amount of silvered foliage was related to the amount of mycelium present in the wood. Injection of 0.5% 8‐hydroxyquinoline potassium sulphate (Oxine KS) at different times in the season increased the volume of diseased wood, but there was evidence that it reduced the density of active fungal mycelium in the wood. No permanent reduction in disease symptoms was found to result from the injection of either Oxine KS or griseofulvin.
The epidemiology of apple scab (Venturia inaequalis (Cke.) Wint.)
Authors: HIRST J.M. , STEDMAN O.J.
Published: February 2008

The liberation of Venturia inaequalis ascospores in orchards is subject to many variables, some of which were studied in the laboratory either in a wind tunnel of approximately 1 ft. square cross‐section or in four smaller tunnels where the annual ascospore production from replicated, small, uniform area samples of dead apple leaf could be compared.

Dew releases some ascospores, but very few compared to rain. The equivalent of 0.2 mm. of rain applied evenly with an atomizer released very many. Some small daytime releases occurred in dry weather but followed wetting at night, either by rain or dew. In orchards 75% of the spores released by brief rains were liberated within 3 hr.; for rains of all durations the comparable figure was 6 hr. Despite the part rain plays in release, there were more ascospores on average in the air at the middle of the day than at any other time, a distribution not shared by rain. This discrepancy could not be explained by the individual effects of light, the time elapsed between wettings, or by temperature (except when very close to freezing point). Observations of the release when atmospheric turbulence was constant or slight suggested that the smaller liberation at night could result from the interaction between temperature and the time for maturation since the previous wetting.

When wetted at weekly intervals, the maturation of ascospores followed an approximately normal distribution, although the peak was often narrow. The distribution could be modified by changing environmental factors, such as temperature and moisture, or the date when the leaves were collected. Tests of these factors were used to formulate a routine laboratory method for comparing the annual ascospore productivity of a standard area of dead leaf. It can be used to assess the ascospore potential of variously treated small plots, or of leaf samples from different varieties and localities. It allows new methods to be introduced for studying ascospore discharge by Venturia and other fungi. Although current experimental designs and the high variability of samples restricted its usefulness to distinguishing large differences, such differences are common, and their existence suggests that the control of apple scab could be improved by attacking the overwintering ascospores.
Some observations on the joint action of insecticides upon adult mosquitoes
Authors: HADAWAY A.B. , BARLOW F. , TURNER C.R.
Published: February 2008

The joint action of insecticides on adult female mosquitoes, Aedes aegypti and Anopheles stephensi, has been studied by topical applications of known dosages separately and in mixtures. Results indicated that the two organophosphorus compounds, malathion and diazinon, have a similar action on the mosquitoes. Responses to mixtures of an organophosphate (malathion) and a carbamate (Sevin), an organo‐phosphate (malathion) or a carbamate (Sevin) and a chlorinated hydrocarbon (DDT or dieldrin), and of two chlorinated hydrocarbons (DDT and dieldrin) were less than expected for similar action.

In other experiments in which two insecticides were applied separately with an interval of 48 hr. between treatments, the order of application was of importance. Mosquitoes receiving a sublethal dose of malathion were more susceptible to Sevin, DDT and dieldrin than untreated mosquitoes from the same population, whereas pre‐treatment with Sevin did not influence susceptibility to malathion, DDT and dieldrin.
The effect of temperature and relative humidity on the rate of development and the mortality of Tribolium madens (Charp.) (Coleoptera, Tenebrionidae)
Authors: HOWE R.W.
Published: February 2008

Using wheatfeed as food the rate of development and the developmental mortality of Tribolium madens were studied at 50 and 70%r.h. over a series of constant temperatures between 17.5 and 37.5°C. and additionally at 10, 30 and 90%r.h. at 22.5, 25 and 30°C.

About 80% of eggs hatched at all temperatures except 37.5°C. where only 59% hatched. The egg period was shortest at 35°C; humidity did not affect the duration of this stage.

Larvae failed to reach the pupal stage at 17.5 and 37.5°C. In all other conditions except 25°C. and 10%r.h. larval mortality was below 10%. The rate of larval development increased consistently with rise in temperature at 70%r.h., but at 50%r.h. there was an optimum between 30 and 32.5°C. Larval development was fastest at the higher humidities, except at 22.5°C. where the results were irregular. The populations used at this temperature were heterogeneous and one larva needed over 200 days to pupate. At 20°C. many larvae entered a resting stage when fully grown and some failed to pupate after 350 days, but did so when placed at 25°C. It is suggested that this resting stage might be a diapause.

The duration of the pupal period was not affected by humidity but it decreased at higher temperatures. The sex ratio was significantly different from unity, with a predominance of females.

The lengths of the various stages, that of the total developmental period and the weight of pupae are compared with corresponding data for T. confusum and T. castaneum. In all conditions, these smaller, more important species develop at least as quickly as T. madens. Also the temperature range over which they can breed is wider.
Effects of the ant Lasius niger (L.) on insects preying on small populations of Aphis fabae Scop. on bean plants
Authors: BANKS C.J.
Published: February 2008

Small populations of Aphis fabae were wholly or partially protected by the ant Lasius niger which drove most predators away. Predators eliminated whole colonies of unprotected aphids or persistently restricted their numbers. Protection of the aphid against predators is probably more important than hitherto thought, and may be more important than the other ways in which ants affect the multiplication rate of A. fabae.
The efficiency of cylindrical sticky insect traps and suspended nets
Authors: TAYLOR L.R.
Published: February 2008

The efficiency with which the 5 in. diameter, white, cylindrical sticky trap and suspended tow‐net catch insects was assessed using Johnson's (1950) field comparison of the two with the suction trap recently standardized by Taylor (1962). The aerodynamic efficiency of the sticky trap was also calculated from Gregory's (1951) results. Comparing these two results shows that small insects behave very like inert particles during capture. Efficiency of the sticky trap is almost constant in winds from 2 to 10 m.p.h. Tables are given converting catch of small insects to aerial density in winds from 1 to 10 m.p.h.
Resistance of oats to cereal root eelworm (Heterodera avenae Woll.)
Authors: DAVIES T. GLYN , GRIFFITHS D.J.
Published: February 2008

Tests of cultivated and wild oats for resistance to the cereal root eelworm (Heterodera avenae Woll.) were based on reaction to eelworm attack in the field and examination of root systems for eelworm cysts. Some resistance was found in Avena sativa var. Heine's Silber II: a higher level of resistance occurred in the wild species A. sterilis, which bore no cysts, and in three forms of A. abyssinica, which bore few or none.
The effect of water‐table on beet eelworm, Heterodera schachtii Schm., in a sandy soil
Authors: MORIARTY F.
Published: February 2008

The failure of beet eelworm to develop on host plants in microplots filled with a sandy soil from an infested field at Cantley, Norfolk, was studied. Using artificial water‐tables it was found that by the time the plants were large enough for many eel‐worms to develop on them, soil conditions were too dry for larval hatch and invasion. Hatched larvae invaded and developed when added to microplots, presumably because they were able to survive the dry conditions until wet weather enabled them to invade the roots.

Some areas may be too dry for development of beet eelworm. Conversely, irrigation may encourage beet eelworm.

These experiments showed that the uses of microplots are limited, because conditions in them may differ from those in fields, and they are less manageable than pots.
Tests of spray materials for use against Gloeosporium spp. in apple orchards
Authors: CORKE A.T.K.
Published: February 2008

Five out of six fungicides, applied to apple trees during dormancy, reduced the viability of conidia of Gloeosporium perennans passing in rainwater over the sprayed bark, and suppressed spore production on the acervuli. While mercury greatly reduced spore viability, it was less effective than the other materials in reducing sporulation over a long period; consequently, in the period from treatment to mid‐July, almost as many viable spores were washed from the mercury‐treated trees as from those which had received the less toxic sprays.

On trees treated with mercury in the dormant season, mercury was found throughout the tissues, including the leaves and buds, six months after treatment.
The biological effects of synthetic detergents in the River Lee, Hertfordshire
Authors: HYNES H.B.N. , ROBERTS F.W.
Published: February 2008

The fauna and flora of the River Lee, which consists primarily of sewage effluent, were studied between 1950 and 1961. During this period the detergent content of the effluent rose from about 1 p.p.m. to between 3 and 4 in 1958, after which, because of the introduction of new types of detergent which are destroyed by sewage treatment, it fell steeply to about 2 p.p.m. in 1960. No marked biological changes which could be correlated with the changes in detergent concentration were found, but experiments indicate that the absence or paucity of some plant species from the river may be due to these substances.
Greenhouse evaluation of chemicals for control of powdery mildews
Authors: KIRBY A. H. M. , FRICK E. L.
Published: February 2008

A method is described for the artificial inoculation of large numbers of potted apple rootstocks or barley seedlings with conidia of the appropriate powdery mildew, using settling towers large enough to hold 100 pots, and blowing spores via a central pipe into the upper part of the tower and allowing them to settle on the foliage.

Plants are put in the tower some 24 hr. before introducing the spores, left enclosed for a further 24 hr., and then placed on the bench in a greenhouse with forced ventilation until lesions are clear enough for recording, usually 9 days after inoculation for apple mildew and 7 for barley mildew.

Rooted shoots from stoolbeds of M. III apple rootstock provided suitable material for apple mildew experiments. The largest numbers of lesions per leaf were usually found on the third and fourth leaves down the shoots; records were usually taken on leaves 3 to 5.

For barley mildew, the variety Plumage Archer was found to be suitable. Conidia can be collected and weighed as required, facilitating control over the inoculum load applied in each test. Seedlings are preferred before the second leaf emerges, i.e. before bending or twisting interferes with inoculation.

The method is successful for the study of both the protective and curative effects of chemicals applied by a dipping technique.
Greenhouse evaluation of chemicals for control of powdery mildews
Authors: KIRBY A. H. M. , FRICK E. L.
Published: February 2008

Apple rootstocks placed in the settling‐tower 24 hr. before introduction of spores of Podosphaera Zeucotricha developed more lesions than those placed in position immediately before inoculation; a period of 24 hr. in the tower after introduction of spores induced more infections than one of 48 hr.

Rootstocks kept at high temperature for a few hours immediately on removal from the tower (24 hr. after inoculation) developed only half as many lesions as those maintained at normal temperatures. This effect declined steadily as the heating was applied on successively later days until the 8th day when such heating had no effect.

Plants kept at about 20°C. and a relative humidity not exceeding 70% grew satisfactorily and developed very similar numbers of lesions to those inoculated in the same tower but subsequently incubated in a greenhouse where R.H. reached saturation every night. High humidity therefore is unnecessary for the inoculation and development of apple mildew.

The leaves initially produced by rootstocks potted in John Innes No. I compost and watered daily with ammonium nitrate solution, were no more susceptible to powdery mildew than those on similar plants given water only. However, when such rootstocks were grown for several weeks, cut back to a few buds, and allowed to break again, the leaves were larger and more susceptible if ammonium nitrate was given as a 0·005 to 0·015 M solution.

The susceptibility of leaves on M. III rootstocks decreased with age by about 50% per leaf‐position down to the fourth and even faster below that position, so that the youngest leaf that is just unrolling is by far the most susceptible.
Host range and properties of grapevine fanleaf and grapevine yellow mosaic viruses
Authors: DIAS H. F.
Published: February 2008

Sap‐transmissible viruses were obtained from grapevines affected by fanleaf, yellow mosaic, distorting mosaic, witches' broom or fasciation diseases. Virus isolates from American, Australian, French and Portuguese grapevines did not differ with country of origin but those from any one country varied in virulence. Herbaceous hosts of isolates originally obtained from grapevines with fanleaf or with yellow mosaic included thirty‐two species in five plant families; yellow mosaic isolates usually caused distinctive symptoms in systemically infected leaves of Chenopodium amaranticolor, but in many other hosts could not be distinguished from fanleaf isolates. Yellow mosaic and fanleaf diseases were each reproduced by transmitting the respective isolates back to grapevine from C. amaranticolor. Grapevine fanleaf and grapevine yellow mosaic viruses were both transmitted through seed of C. amaranticolor; both were precipitated without inactivation by ethanol, by acetone, by ammonium sulphate and at pH 5. Preparations of each, partially purified from systemically infected leaves of Nicotiana clevelandii, contained polyhedral particles about 30 mp in diameter. Phenol‐disrupted virus was 1–5% as infective as its parent virus suspensions.
The relationship between grapevine fanleaf, grapevine yellow mosaic and arabis mosaic viruses
Authors: DIAS H. F. , HARRISON B. D.
Published: February 2008

Plant protection and serological tests showed that the viruses causing the grapevine fanleaf and grapevine yellow mosaic diseases occurring in Portugal, Switzerland and the United States are closely related strains. These strains and arabis mosaic virus cause similar symptoms in many herbaceous species, but arabis mosaic virus is more virulent and more often becomes systemic. Attempts to transmit arabis mosaic virus to grapevine failed. Arabis mosaic virus shares only few antigenic determinants with the viruses obtained from grapevine, and these viruses do not protect plants against it. In a virus classification, the grapevine virus isolates and arabis mosaic virus can be considered two distinct serotypes of one virus.

The nematode Xiphinema diversicaudatrim acquired arabis mosaic virus and transmitted it to herbaceous plants but did not transmit the grapevine viruses. As X. index is known to transmit grapevine fanleaf virus and probably transmits grapevine yellow mosaic virus, this suggests specific transmission of virus serotypes by different species of nematodes.
Investigations on fungicides
Authors: CARTER G. A. , GARRAWAY J. L. , SPENCER D. M. , WAIN R. L.
Published: February 2008

The structure/anti‐fungal relationships of a group of 137 sulphur‐containing compounds were studied by observation of their effects on the mycelial growth of six fungi, Pythium ultimum, Sclerotinia fructigena, Verticillium albo‐atrum, Alternaria solani, Botrytis cinerea and Aspergillus niger, and the germination of spores of Botrytis cinevea. These compounds consist of (a) salts and (b) carboxy‐alkyl and ‐alkenyl esters of both alkyl‐ and aryl‐substituted dithiocarbamic and hydroxydithioformic acids, (c) certain cyclic derivatives of (b), and (d) alkyl and aryl isothiocyanates. Short homologous series were selected to assess the importance of physico‐chemical properties in fungitoxicity, whilst certain aryl‐substituents were used on the basis of their contrasting electronic effects.

Derivatives of alkoxydithioformic acids showed higher toxicity than those of N‐alkyl‐substituted dithiocarbamic acids, except for a series of β‐(N‐alkylthio‐carbamoylthio)acrylic acids. The fungitoxicity of esters of alkyl‐substituted dithiocarbamic or hydroxydithioformic acids showed little change on increasing the size of the alkyl substituent or ester grouping. The fungitoxicity of compounds derived from N‐aryldithiocarbamic acids varied considerably with the nature of the N‐substituent.
Investigations on fungicides
Authors: BATES ANGELA N. , SPENCER D. M. , WAIN R. L.
Published: February 2008

Four series of aliphatic nitro compounds have been synthesized and examined for their fungistatic effects in mycelial growth tests. On the basis of the results nine compounds were selected for further study in spore germination tests and as fumigants. They were also examined for protectant and systemic fungicidal activity using broad bean seedlings. A special method was adopted in assessing activity as systemic fungicides whereby fumigant action could be avoided.
Studies on plant growth‐regulating substances: XVII. S‐esters of dithiocarbamates derived from amino acids
Authors: ROTHWELL K. , WAIN R. L.
Published: February 2008

A further study of plant growth‐regulating activity in compounds not possessing a ring structure has been carried out. For this purpose a range of N‐substituted S‐esters of dithiocarbamates derived from amino acids was synthesized and their activities were assessed in the wheat cylinder, pea segment and pea curvature tests. The highest activity in all tests was shown by S‐methyl‐N‐methyl‐N‐carboxymethyl dithiocarbamate, CH3N(CH2COOH)C(: S)SCH3. N‐substituents other than methyl reduced the activity, whereas a group other than methyl attached to the sulphur atom destroyed activity.

The infra‐red spectra of the compounds have been used to study the nature of the N‐C bonding within the molecules and this and other factors are discussed in relation to growth‐regulating activity.
A method of isolating Pythium spp. and Fusarium oxysporum from soil
Authors: BUXTON E. W. , KENDRICK J. B.
Published: February 2008

Weighed amounts of lightly pulverized soil were drawn through a perforated aluminium plate and impacted on agar media in Petri dishes. This was done by placing the dishes in an Andersen air sampler, through which air was drawn at 14 l./min. The sampler was operated so that the soil was dispersed uniformly into 400 equally sized units/dish, each unit weighing 0·125 mg. These were transferred either to water‐agar medium to detect Pythium spp., or to Dox‐yeast‐agar medium for Fusarium oxysporum. The amount of each fungus in the soil was estimated from the frequency it was recovered from the transferred soil units. Results were more reproducible than by the usual soil‐dilution methods, and the method gave more uncontaminated cultures of Fusaria and Pythia.
Reactions of tomato leaves to species of Verticillium
Authors: GRIFFITHS D. A. , ISAAC IVOR
Published: February 2008

Mycelium developing from germinating spores of Verticillium tricorpus, supplied with an adequate source of carbohydrate, penetrated healthy but not wounded tomato leaves, whereas V. dahliae, originally isolated from Brussels sprouts, invariably failed to enter a living leaf. Colonization by V. tricorpus ceased when the lamina became chlorotic and was followed quickly by premature leaf‐fall. Whereas leaves killed by immersing in boiling water were quickly invaded by V. tricorpus and V. dahliae, fallen leaves which had died naturally appeared to have on their surfaces a substance which had an inhibiting effect upon the germination of conidia of both fungi.

Expressed sap from living leaves contained a water‐soluble thermolabile substance which inhibited the germination of, but was not lethal to, conidia suspended in distilled water, but its action was suppressed by the presence of sucrose.

It is suggested that this inhibitor, probably in a bound state in the living leaf, on death passed out through the now completely permeable cell membranes on to the surface in a sufficient concentration to prevent the germination of the conidia.
Abacá mosaic virus and its relationship to sugar‐cane mosaic
Authors: ELOJA A. L. , TINSLEY T. W.
Published: February 2008

Abacá mosaic virus (AMV), which is readily transmissible between maize seedlings by inoculation with sap, has properties suggesting that it is a strain of sugar‐cane mosaic virus. Antisera to AMV precipitated specifically with sap from plants infected with the strain of sugar‐cane mosaic virus found, in Puerto Rico. Partially purified preparations of AMV contained flexuous rods 680 mμ long similar to those recorded for sugar‐cane mosaic virus.

No evidence was found to support the widely held view that AMV is a strain of cucumber mosaic virus. Cucumber mosaic may infect abacá, but it is certain that other viruses can cause typical symptoms of abacá mosaic.