bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of three organo‐phosphorus insecticides on certain arthropods which infest livestock
Authors: BEESLEY W. N.
Published: February 2008

The organo‐phosphorus compounds fenchlorphos, trichlorphon and coumaphos, used at 0·25%, killed Dermanyssus gallinne on poultry and perches, and Leiognathus (Liponyssus) sylziarum on poultry: both showed persistent acaricidal value without avian toxicity.

Fenchlorphos at 100 mg./kg. and trichlorphon at 20–100 mg./kg. were systemically effective against larvae of Lucilia sericata on sheep. Coumaphos was non‐insecticidal, but toxic to sheep, when given orally at 15–20 mg./kg. Sprzying with 0·25% coumaphos protected sheep against L. sericata larvae for 8–10 weeks.

Fenchlorphos administered orally at 110 nig./kg. killed larvae of Hypoderma boris which had been implanted into calves. Trichlorphon (2·0%) applied externally killed all larvae within 28 days: coumaphos (2·0%) similarly applied was larvicidal within about 15 days.

The toxic dose of fenchlorphos for calves was 500 mg./kg.; trichlorphon at 300 mg./ kg. and coumaphos at 20 mg./kg. were toxic to sheep.
A preliminary study of the effect of physical activity on the resistance of rainbow trout (Salmo gairdnerii Richardson) to two poisons
Authors: HERBERT D. W. M. , SHURBEN D. S.
Published: February 2008

The toxicity of zinc sulphate and ammonium chloride to rainbow trout forced to swim continuously against water currents of three known velocities has been compared with their toxicity to similar fish tested simultaneously in still water. For fish swimming at 85% of the maximum sustainable velocity the concentration of ammonium chloride killing 50% at 24 hr. was 0·81 times that for still water, and the corresponding factor for 48 hr. exposure to zinc sulphate was 0·70. Current speeds up to 55% of the maximum sustainable velocity produced no detectable increase in susceptibility to either poison. The increase in metabolic rate with current velocity was measured, and its relation to the increase in susceptibility to poisons is discussed.
The influence of temperature on the emergence of the cabbage root fly (Erioischia brassicae (Bouché)) from overwintering pupae
Authors: COAKER T. H. , WRIGHT D. W.
Published: February 2008

The pupae of Erioischia brassicae (Bouché) overwinter in diapause, which extends for 105–126 days at a constant temperature of 41° F. (5° C.) and terminates, in the field, between the end of January and the beginning of February. Morphogenesis is completed at constant temperature after an accumulation of about 368 day degrees above 42° F., and in the field at Wellesbourne the first flies usually emerge during April.

Phenological relationships of emergence and beginning of oviposition with accumulated day degrees and the flowering of Anthriscus sylvestris appear to provide reliable methods for the prediction of the emergence of the first flies and for the determination of the appearance of the first eggs in the field.
The systemic action of benzene hexachloride seed dressings
Authors: BRADBURY F. R.
Published: February 2008

Wheat seedlings absorb γ‐BHC freely when grown with their roots in a saturated water solution of the insecticide but less than 10 % of the γ‐BHC applied as a seed dressing finds its way into the plants from treated seed grown in compost. About the same proportion of the dressing is absorbed by cabbage seedlings grown from treated seeds, although the usual rate of application is higher in this case. The brassica seems better able than wheat to absorb the insecticide, with the result that concentration of γ‐BHC expressed as μg./g. fresh weight is greater and it is maintained for longer in cabbage than in wheat.

The rate of loss of γ‐BHC from soil is shown to be slow compared with the expected life of a seed dressing.

Phytotoxic damage to wheat seedlings grown from seed dressed at 1000 p.p.m. γ‐BHC was evident when they were planted in sand but not in compost. Particle size of γ‐BHC in the dressing appeared to be without effect on phytotoxicity.
The relationship of insects, fungi and nematodes to the deterioration of roots of Trifolium hybridum L.*
Authors: LEACH C. M. , DICKASON E. A. , GROSS A. E.
Published: February 2008

To evaluate the relative importance and possible interrelationships of insect, fungus, and nematode injury to the deterioration of roots of alsike clover plants, Trifolium hybridum L., heptachlor, chloropicrin, and ethylene dibromide were applied singly and in combinations to the soil prior to seeding. The most effective treatment was an insecticide plus a soil fumigant (heptachlor plus chloropicrin or ethylene dibromide), which improved the uniformity of stand, plant height and flowering, and reduced the density of weeds. In the second year this treatment greatly increased plant survival and yields of forage. All the plants died in the untreated control plots during the third year of the experiment.

There was a significant relationship between the occurrence of vascular decay and the incidence of injury by the clover root curculio, Sitona hispidula (Fabr.). There was a less marked relationship between insect injury and cortical decay; but no apparent relationship between insect injury and rootlet rot. Although root lesion nematode, Pratylenchus sp., was present, no direct relationship between nematode injury and root rots was established.

The fungi most frequently isolated from alsike clover roots were Fusarium oxysporum Schl. sensu Snyd. and Han., a species of Pyrenochaeta and an unidentified fungus. Verticillium dahliae Kleb. was also present. Tests with F. oxysporum, the Pyrenochaeta sp., and V. dahliae confirmed their pathogenicity on alsike clover roots. In laboratory tests, plants with severe rootlet rot rapidly regenerated feeder rootlets in the presence of adequate soil moisture.
Pyricularia grisea(Cooke) Sacc. causing pitting disease of bananas in Central America
Authors: MEREDITH D. S.
Published: February 2008

Dark‐coloured, depressed spots (‘pits’), up to 10 mm. in diameter, are recorded on Giant Cavendish banana fruits in Costa Rica. Pits first appear in the field, usually on almost mature bunches, and increase in numbers during cold storage and ripening. Symptoms are identical with those of ‘Johnston fruit‐spot’ and ‘pitting disease’ described by earlier workers. Disease is maximal during and for a short time after heavy rainfall.Pyricularia griseawas consistently isolated from typical pits, and disease was reproduced by inoculating fruit in the field with conidia of P.griseafrom pure culture. Conidia germinate after 1–2 hr. in a film of water on the peel of immature fruits. An appressorium is formed and there is some evidence that this produces an infection hypha which, in the first instance, penetrates the cuticle but not the epidermis cell wall. In most cases, there is no evidence of further penetration until the fruit is ready for harvest, or until after harvest. The fungus then resumes activity and invades the epidermis and underlying tissues to cause a pit. Latency in P.griseais compared with that inGloeosporium musarum.
Effects of mineral nutrition on the production of tulip bulbs
Authors: CHEAL W. F. , HEWITT E. J.
Published: February 2008

Two varieties of tulip, Golden Harvest and Elmus, of selected bulb weight ranges, were grown in sand culture with different levels of nitrogen, phosphorus and potassium in factorial combination, and at different levels of magnesium.

The effects of nitrogen were dominant, but the levels giving optimal bulb yields differed for the two varieties. Potassium and magnesium had smaller, but significant, effects and there were significant interactions between nitrogen and potassium.

The weight distribution for all daughter bulbs produced from a single planting bulb was discontinuous in certain ranges. Nitrogen had an outstanding influence on the pattern of bulb multiplication, which also reflected a nitrogen/potassium interaction. Responses in weight distribution, as in total bulb production, showed both varietal and seasonal differences.
Studies on the lettuce big‐vein virus and its vector Olpidium brassicae (Wor.) Dang
Authors: TOMLINSON J. A. , GARRETT R. G.
Published: February 2008

It was demonstrated by serial graft transmission experiments that the big‐vein disease of lettuce was caused by lettuce big‐vein virus (LBVV).

An Olpidium sp., always found in the roots of naturally affected plants, induced the disease when its zoospores were transferred to healthy plants. The fungus was identified as O. brassicae (Wor.) Dang.

The same fungus was found in the roots of healthy lettuce, but zoospores from this source would not induce big‐vein when transferred to healthy plants.

When a non‐viruliferous isolate of O. brassicae was grown in the roots of lettuce affected by big‐vein the fungus acquired LBVV and was able to transmit the disease. Conversely, the viruliferous Olpidium was converted to a non‐viruliferous form by culture in the roots of Plantago major or Veronica persica. These results were not caused by the selection of non‐vector strains of the fungus during its culture in these species, as the fungus reacquired and transmitted LBVV when again cultured in big‐vein affected lettuce roots. The results suggested that LBVV did not multiply in P. major or V. persica, or in the fungus during its growth in them.

Attempts to transmit LBVV with Cuscuta campestris, C. gronovii, C. reflexa and C. subinclusa and by sap inoculation were unsuccessful.

No causal relationship between tobacco necrosis virus (TNV) and big‐vein was found: the reasons for the frequent association of TNV with the disease are discussed.
A quantitative laboratory method for inoculating cabbage seedlings with Plasmodiophora brassicae Woron
Authors: CHANNON A. G. , FLINT ANNE E. , HINTON R. A. L.
Published: February 2008

In studies on root‐hair and rhizodermal cell infection of cabbage seedlings by Plasmodiophora brassicae Woron. seeds were germinated in an incubator at 25°C. on nylon mesh circles placed on glass dishes containing nutrient solution. After 3 days the original nutrient solution was replaced by a similar one containing a known quantity of resting spores of the fungus. After a further 5–7 days in the incubator the roots were removed and stained. The infected plants were counted and the extent of infection on each plant was assessed in grades 0–4.

Optimal infection was obtained by using spores from decomposing clubbed roots, by thoroughly washing the resting spores, and by using thirty plants per dish grown from seed of 1·5‐2·0 mm. diam. There was a rapid increase in infection from the 3rd to the 6th day after introduction of the spores.

Infection of large numbers of seedlings was easily obtained by this technique, which is now being used for assessing the effects of chemicals in controlling clubroot.
Studies on sharp eyespot disease of cereals
Authors: PITT D.
Published: February 2008

Several isolates of Rhizoctonia solani Kühn were obtained from wheat stems bearing lesions of sharp eyespot in the summers of 1960 and 1962. Differences in virulence of these isolates, assessed by severity of attack on seedlings, were demonstrated. Isolates taken from different plants in the same crop were shown to differ in virulence. All isolates obtained from wheat‐stem lesions attacked both winter and spring varieties of wheat, barley, oats and rye. Several varieties of spring and winter wheats showed no differences in susceptibility to disease.

Infection of the wheat host took place at any time during the growing period, but was most severe in the earlier stages of growth.

Sharp eyespot occurs over a wide range of soil types, but the most severe attacks all occurred on lighter soils with neutral to slightly acid pH. Sand‐culture experiments showed no effect of pH on disease development over the range 5·9‐8·1. Disease development in seedling wheat plants was favoured by cool (9·3°C.) dry (ca. 20% of the water‐holding capacity) conditions in the greenhouse. Disease incidence in the field over the period 1959‐63 could be correlated with the weather conditions prevailing over this time.
The effects of black‐currant yellows virus and a strain of reversion virus on yield
Authors: CROPLEY R. , POSNETTE A. F. , THRESH J. M.
Published: February 2008

Black‐currant yellows virus restricted the growth of bushes var. Baldwin and Wellington XXX and decreased the total weight of fruit harvested in six seasons by 70%. The size and number of fruits were decreased and in one season ripening was retarded. Virus spread naturally to only four of 250 other bushes in the trial.

A strain of reversion virus which caused transitory vein‐pattern symptoms did not restrict vegetative growth, yet decreased the number and size of fruits. In contrast to the more severe effects of prevalent virulent strains, the total crops from the Wellington XXX and Baldwin bushes were decreased by 50 and 33% respectively. The virus spread to fifteen of the 136 healthy bushes and to at least six of the 108 bushes previously infected with yellows virus.

The black‐currant gall mite (Phytoptus ribis Nal.) increased more rapidly on the Wellington XXX bushes than on those of Baldwin. In each variety the infestation was much greater on reverted than on other bushes, apparently because infection with reversion virus decreased natural resistance to mites.
The epidemiology of tomato mosaic
Authors: BROADBENT L.
Published: February 2008

Four experiments were done under glass in which tomato plants were inoculated with TMV (tomato strains of tobacco mosaic virus) at different times during their growth, and most of the healthy control plants were kept uninfected throughout the season. Leaf symptoms were visible 2–3 weeks after inoculation, and infected plants were checked and grew more slowly than healthy ones. Leaves of infected plants were sometimes scorched by overhead damping with water, and lower leaves died earlier than those of healthy plants.

In the 1960 experiment, with a winter‐sown crop, plants inoculated on 3 March, when the first trusses began to flower, suffered a 15% loss in weight of fruit; those inoculated on 14 April, when the fifth trusses began to flower, an 18% loss, and those inoculated on 31 May, when most of the fruits had set, a 14% loss. The two early infections caused 13% fewer fruits to set, but the last one only 3% fewer; however, with successively later infection dates, mean fruit size progressively decreased. Fruit quality was severely affected by later infection, 10% of the fruits from plants infected in April showing necrotic pitting, bronzing or severe mottle, but 31% of those infected on 31 May.

Three experiments with spring‐sown plants gave similar results. In the 1961 experiment, plants inoculated on 3 May, when the first trusses began to flower, yielded 21% less weight of fruit than the controls, and those inoculated on 8 June, when the fifth trusses began to flower, 14% less. A tobacco strain of TMV that caused no symptoms in tomato failed to protect plants from later infection with a tomato strain. In the 1962 experiment, seedlings inoculated on 13 March, just after pricking out, yielded 10% less weight of fruit; plants inoculated on 4 April, just after planting out, 3% less; those inoculated on 3 May, when the first trusses began to flower, 11% less; and those inoculated on 7 June, when the fifth trusses began to flower, 16% less. In the 1963 experiment, plants inoculated on 21 May, when the first trusses began to flower, yielded 17% less weight of fruit than the controls, and those inoculated on 20 June, when the fifth trusses began to flower, yielded 23% less; many of the control plants became infected during August in this last experiment. As in the first experiment, losses were largely due to poor setting of fruits at the time the plants became systemically infected with virus, and necrotic pitting and severe bronzing again mainly affected fruits from the late‐infected plants. The plants grew vigorously and were ‘soft’ or lush in all the four experiments.
Powdery mildew of tobacco (Erysiphe cichoracearum DC.)
Authors: COLE J. S.
Published: February 2008

In water culture experiments, tobacco plants of Hicks variety were supplied with factorial combinations of high and low concentrations of nitrogen, phosphorus and potassium. Incidence of powdery mildew and growth and chemical composition of infected and healthy plants were compared.

There was more disease when all elements were supplied at the higher of two concentrations, but the increase in infection was less than the increase in growth. Plants grown in media containing a low ratio of potassium to nitrogen produced the least susceptible leaves; their disease indices were up to 30 times less than those of plants that received the full nutrient treatment. Potassium‐deficient leaves had thinner cell walls, larger water content, smaller sugar and potassium contents, and greater amino nitrogen and magnesium contents, compared with those of plants grown in any of the other media. The possible relation between these characteristics and susceptibility to Erysiphe cichoracearum DC. are discussed.
The effect of high temperatures on aqueous suspensions of stem eelworm, Ditylenchus dipsaci (Kühn) Filipjev
Authors: GREEN C. D.
Published: February 2008

The relationship between the time and temperature necessary for killing Ditylenchus dipsaci in hot water suggests that the cause of death at 48° is different from that below 46° C. The ability of nematodes, which survived one hot‐water treatment, to recover their resistance so as to survive a second hot‐water treatment and yet to show a susceptibility to storage temperatures which are not lethal to untreated nematodes, supports the view that there are at least two causes of death after heat treatment.

Acclimatization increases the heat resistance of the nematodes and would cause failure of hot‐water treatment as a control measure against bulb eelworm. Storage at temperatures of 25–30° C. after hot‐water treatment increases the proportion of dead nematodes and, if applied to bulbs, might improve control. The effects of such temperatures before and after hot‐water treatment are not due to heat shock following the sudden rise or drop in temperature.
Growth of Picea sitchensis in old forest nurseries
Authors: REDDY M. A. RAM , SALT G. A. , LAST F. T.
Published: February 2008

The poor yield of Sitka spruce (Picea sitchensis Carr.) seedlings in old forest nurseries at Kennington and Ringwood results from losses of seedlings during germination, and stunted growth of those that survive.

Losses, which are attributed mainly to invasion by Pythium spp. and secondarily by Cylindrocarpon radicicola Wr. and Fusarium spp., were decreased by (a) partially sterilizing soil with formalin, dazomet or metham‐sodium, (b) applying the fungicides maneb and quintozene to soil, and (c) dressing the seed with fungicides. In contrast, only partial sterilization increased growth of the survivors.

Fungicidal seed‐dressings, which did not affect growth, increased numbers of survivors most in partially sterilized soils, suggesting that soil microfloras developing after partial sterilization controlled seed‐borne pathogens no more effectively than do the microfloras of unsterilized soils.

Experiments with transplants indicated that the growth stimulus from partial sterilization operated equally at all stages of seedling development, and was independent of root damage done by parasites.
The toxicity of some insecticides to first‐instar nymphs of the desert locust, Schistocerca gregaria (Forsk.)
Authors: MacCUAIG R. D. , YEATES MAUREEN N. D. B.
Published: February 2008

The toxicities of γ‐BHC, diazinon, dieldrin, DNOC, heptachlor and parathion to first‐instar hoppers of the desert locust were determined. Parathion was the most toxic followed in descending order of toxicity by dieldrin, γ‐BHC, heptachlor, diazinon and DNOC. Results with diazinon showed a non‐linearity of the probit/log. dose regression line. Changing the post‐treatment temperature from 26 to 31° C. had no effect on the final toxicity of the insecticides, excepting that of dieldrin which was 1·48 times as toxic at the higher temperature.
The toxicity to fish of mixtures of poisons
Authors: HERBERT D. W. M. , SHURBEN D. S.
Published: February 2008

Experiments have been made with rainbow trout in solutions of ammonium chloride and zinc sulphate to examine the empirical rule that a mixture of two poisons, P and Q, should be at the threshold concentration for acute toxicity when PS/PT + QS/QT= I, where the suffix S stands for the concentration in solution and T for the threshold concentration of a poison when tested by itself. The most detailed experiment, with a hard dilution water in which the dissolved‐oxygen concentration was at the air‐saturation value, gave results within 4% of those expected from the hypothesis. Agreement was not so close in a soft dilution water, nor in a hard dilution water containing a reduced concentration of dissolved oxygen, but in these two cases the threshold concentrations for the mixtures were within 26 and 17% of the expected value of unity. In every case the rule under examination provided a better description of the data than models based on the hypothesis of independent joint action.
Investigation of carnation viruses
Authors: HOLLINGS M. , STONE OLWEN M.
Published: February 2008

Carnation mottle virus (CarMV) was present in every plant tested of over forty‐four varieties from commercial carnation stocks. Inhibitors of infection in carnation sap prevent transmission to many species, but not to Chenopodium amaranticolor, which proved the best indicator and assay host. CarMV infected thirty‐three of 113 plant species inoculated, but only Dianthus spp. are likely to be affected in practice. Healthy carnations were infected when handled after diseased ones. CarMV was not transmitted by Myzus persicae, through carnation seed, or through dodder (Cuscuta campestris).

The type strain occurred in all ‘Sim’ carnations tested; another strain, designated ‘PSR’, occurred in vars. Pink Shibiuya and Orchid Beauty. The two strains were distinguished by the symptoms caused in Chenopodium amaranticolor and other plants. The type strain protected against the PSR strain in Atriplex hortensis. An ‘attenuated’ form of the virus, which multiplied much more slowly than the typical form, withstood adverse conditions better.

Although the virus concentration decreased in the terminal 1–2 mm. of the carnation shoot apex, CarMV was always detected in the meristem dome. Nevertheless, some virus‐free clones were obtained by aseptic culture of excised tips. CarMV was not eliminated by growing plants at 38°C., although its concentration in the apical tissues was diminished.

Sap was infective after dilution to I/200,000, heating (10 min.) to 85°C. (but not 90°C.), storage for up to 81 days at 18°C., or over 3 years at o°C. Purified and concentrated preparations of CarMV were readily obtained from carnation by several methods: they contained ‘spherical’ particles about 28 mμ diameter, were antigenic, and produced a specific light‐scattering virus zone in density‐gradient centrifugation. The S20,w at infinite dilution was 122.

Although CarMV shares many in vitro properties with eleven other viruses having similar particle shape, it is not serologically related to any of them and differs in other respects.

Control of the virus depends on the production and distribution of virus‐free clones of carnation.
Some effects of other viruses and of temperature on the multiplication of potato virus X
Authors: CLOSE R.
Published: February 2008

The severity of symptoms shown by tobacco plants infected with potato virus X (PVX) was correlated with virus concentration. The virus multiplied optimally between 20 and 24deg;C. and increasing temperature above 25°C. decreased symptoms and virus concentration. PVX did not multiply detectably in plants at 34°C.

Tobacco leaves systemically infected with both PVX and potato virus Y (PVY) contained more PVX than leaves infected with PVX alone. The greatest relative increase was at 31°C. because at this temperature PVX alone barely multiplied and failed to move out of the inoculated leaf. The concentration of PW was not altered by the presence of PVX and the optimum temperature for its multiplication appeared to be 28°C. Three other viruses (namely tobacco mosaic virus, cucumber mosaic virus (yellow strain), and henbane mosaic virus) that multiply at 31°C. also assisted the systemic spread of PVX at this temperature, possibly by aiding its movement between mesophyll cells and into the phloem. PVY may also aid PVX at lower temperatures mainly by increasing the number of cells it infects.
The currant clearwing moth (Aegeria tipuliformis (Clerck)) as a pest of black currants
Authors: BROCK A. M. , COLLINGWOOD C. A. , WHITE J. H.
Published: February 2008

The bionomics of the currant clearwing moth in a heavily infested Lincolnshire black currant plantation were investigated from 1951 to 1960. 95% of overwintered larvae pupate in May; the remainder, chiefly in the older wood, carry over until the following season. The mean number of eggs laid per bush was ninety and the mean number of larvae surviving until winter was forty‐nine (59,000/acre). Pruning, parasitism and predation by tits reduced this to twenty by May, giving an overall loss of about 80% from egg to adult due to natural causes.

Parathion, dipterex or gusathion, acting ovicidally, reduced surviving larvae by 80% compared with untreated controls, but a large‐scale experiment showed no crop increase in the year following successful treatment and the net economic effect of high larval infestation was negligible.
Estimation of slug populations
Authors: SOUTH A.
Published: February 2008

It is impracticable to count slugs per unit area in the field, but both slugs and their eggs are recovered efficiently by soil washing in the laboratory. A less laborious method is described in which slugs (only) are expelled from turves progressively immersed in cold water. This method, used with samples of twelve 12×12×4 in. units of substratum, gives satisfactory estimates for Agriolimax reticulatus and Arion intermedim at population densities above I per sq.ft.
On the systematic position of the coliform bacteria responsible for stalk rot of maize
Authors: SABET K. A. , SAMRA A. S. , EL‐SHAFEY H. A.
Published: February 2008

Comparative studies were made of two isolates of the Egyptian strain of the maize stalk‐rot bacterium (Erwinia carotovora f. zeae Sabet), one isolate of the Indian strain of the same pathogen, two isolates of the cause of stalk rot in U.S.A. named E. maydis, and several isolates of E. carotovora from different hosts and different parts of the world. It was shown that these pathogens are closely related in their cultural and morphological characters but somewhat variable in certain biochemical reactions. They agree in their pathogenicity and relation to environment. The differences between E. maydis of Kelman, Person & Hebert (1957) and E. carotovora were found to be well within strain variation and do not justify the creation of a new species. The stalk‐rot bacteria from U.A.R., India and U.S.A. are distinguished by their ability to attack certain graminaceous plants which no other strain of E. carotovora can infect. It is concluded on this ground that the name originally adopted by Sabet (1954), i.e. E. carotovora f. zeae should be maintained and applied to the organism causing stalk rot in U.S.A.
Necrotic ring spot and prune dwarf viruses in Prunus and in herbaceous indicators
Authors: CROPLEY R. , GILMER R. M. , POSNETTE A. F.
Published: February 2008

When scions from sweet cherry trees with tatter‐leaf disease were used to infect a range of Prunus species they induced necrotic leaf spot and stunt in peach, prune dwarf in Italian Prune and necrotic leaf spot and yellows in sour cherry. Inoculum prepared from such infected sweet cherry leaves caused two types of lesions on inoculated cucumber cotyledons from which single‐lesion cultures yielded two viruses differing in physical properties and herbaceous host ranges.

One of these viruses reacted with antiserum prepared against a North American isolate of necrotic ring spot virus and, when returned from cucumber to Prunus, it caused tatter‐leaf in sweet cherry, necrotic leaf spot in peach and sour cherry, and no symptoms in Italian Prune. The other virus, which reacted with antiserum prepared against a North American isolate of prune dwarf virus, caused prune dwarf in Italian Prune, stunt in peach and only slight leaf necrosis in sweet cherry. Sour cherry trees developed yellows only when infected with both viruses, but in sweet and sour cherry infection with one virus reduced the severity of the necrotic shock symptoms induced by the other.
Further studies on European rasp‐leaf and leaf‐roll diseases of cherry trees
Authors: CROPLEY R.
Published: February 2008

Cherry leaf‐roll, raspberry ringspot and arabis mosaic viruses occurred in high concentration in cherry sap extracted from buds or from young leaves in the spring. The viruses could be detected serologically in crude cherry sap which was highly infective to herbaceous test plants. During summer and autumn infectivity of leaf‐roll virus decreased in cherry sap, while a virus inhibitor increased.

Each virus was transmitted by inoculation with sap from herbaceous host plants to young Prunus seedlings and from these to mazzard F12/1 and Bing sweet cherry plants by grafting. Cherry leaf‐roll virus caused leaf rolling and a few very small enations on the undersurfaces of Bing leaves. Raspberry ringspot virus and one strain of arabis mosaic virus induced small enations characteristic of mild rasp‐leaf disease. When plants infected with these viruses were also infected with Prunus necrotic ringspot virus, the symptoms were only slightly enhanced whereas they were very severe when prune dwarf virus was added.

Rasp‐leaf disease may increase by the spread of prune dwarf virus in orchards where latent infection with raspberry ringspot virus had occurred previously. In other orchards, trees may develop the disease as raspberry ringspot virus spreads into trees already infected with prune dwarf virus.
The toxicity to fish of mixtures of poisons: II. Copper‐ammonia and zinc‐phenol mixtures
Authors: HERBERT D. W. M. , VANDYKE JENNIFER M.
Published: February 2008

Tests with rainbow trout in mixtures of ammonium chloride with copper sulphate and of phenol with zinc sulphate have shown that the threshold of toxic concentration for a 50% mortality occurs in solutions for which a value of I is obtained by summing the concentrations of the individual poisons expressed as fractions of their individual threshold concentrations. With ammonia‐copper mixtures this method of predicting the threshold concentration becomes progressively less adequate as lower percentage mortalities are considered.
Glasshouse experiments on apple scab I. Foliage infection in relation to wet and dry periods
Authors: MOORE M. H.
Published: February 2008

A technique of investigating apple scab infection periods using MM 109 rootstocks in the glasshouse is fully described. Inoculation by ascospores in aqueous suspension was less reliable than that by sedimenting the spores direct from source leaves on to the host plants, but fresh conidia in aqueous suspension consistently gave high levels of infection under optimum conditions.

Ascospores required a shorter period of continuous wetness (6 hr.) than conidia (7–9 hr.) for infection at near‐optimum temperatures. Maximum infection from both sources was reached after about 18 hr. continuous wetness; much longer periods were sometimes inimical. With discontinuous wetness, most ascospores tolerated a dry interval of 24 hr. on the host leaves, although infection was somewhat reduced if the dry period began when the spores were starting to germinate. Conidia were more inhibited than ascospores by 24 hr. drying during minimal infection periods, but many survived and produced lesions.

Some ascospores survived dry periods of at least 96 hr., but mature leaves had acquired resistance during the interval and thus infection was reduced. The reduction was partly offset by greater infection of the youngest leaves, which meantime had expanded and were thus easier to wet. No infection resulted, however, when the dry interval was extended to 10 days.

The implications of the results are discussed in relation to the interpretation of infection periods in the field.
Genotype‐environment interactions and developmental rate in the flour beetles Tribolium castaneum and T. confusum (Coleoptera, Tenebrionidae)
Authors: DAWSON P. S.
Published: February 2008

Developmental rates of a number of strains of the flour beetles, Tribolium castaneum and T. confusum, were measured at 40, 60 and 70% relative humidity. Significant genotype‐environment interactions, as well as strain and humidity effects, were observed. The results indicate that the response to different humidities of some strains depends on their genetic composition.
Aspects of trapping slugs with metaldehyde and bran
Authors: WEBLEP D.
Published: February 2008

In trapping slugs, 1 part of 30% Sevin (carbaryl) (1‐naphthyl‐N‐methylcarbamate) to 40 parts of standard metaldehyde‐and‐bran mixture gave an improved catch over standard biscuits. The fungicides dazomet or zineb incorporated in biscuits repelled slugs. It was shown that the fall‐off in the attraction of metaldehyde and bran did not occur until 4 days after biscuit exposure, and that black glass plates placed over pelleted baits masked their effect, the same catch being obtained with one or with sixteen pellets. Even without glass plates there was evidence to suggest that the catch of Agriolimax reticulatus was similar with one or sixteen pellets. The implications of these results on control measures are discussed and it is recommended that metaldehyde sprays be used for epidemics, and the baits only as long‐term measures to keep down infestations already partly controlled.
Resistance to zinc sulphate of the zebrafish (Brachydanio rerio Hamilton‐Buchanan) at different phases of its life history
Authors: SKIDMORE J. F.
Published: February 2008

Zebrafish of eleven age groups were exposed to four concentrations of zinc sulphate (5, 10, 20 and 40 p.p.m. Zn) in soft water (CaCO3 10 p.p.m.) at 25d̀ C. In all four concentrations, newly laid eggs generally survived the longest time. Survival time decreased with age until hatching on the fourth day. Newly hatched fish (4–13 days old) survived the shortest time. Forty‐day‐old fish and adults (100 days old) survived slightly longer in the two highest concentrations. In the two lowest concentrations, 40‐day‐old fish survived as long as newly laid eggs, and many adults survived indefinitely. The threshold concentration of zinc was approximately 10 p.p.m. for adults and 1.3 p.p.m. for 40‐day‐old fish.
Biological control of Fusarium wilt of peas by organic soil amendments
Authors: KHALIFA O.
Published: February 2008

Pure chitin added to soil significantly lessened the severity of pea wilt caused by Fusarium oxysporum f. pisi (Linf.) Snyder & Hansen. Pectin, glucose, cellulose and laminarin had less effect. In the glasshouse the wilt index was diminished by 12 % when chitin was added to inoculated soil the same day pea seedlings were planted in the soil, and by 25 and 45 % when it was added 3 and 8 weeks before transplanting. In the field, applying chitin to naturally infested soil when peas were sown decreased wilt index by 82 and by 75 % when applied 4 weeks earlier.

Chitin did not affect the growth of healthy pea seedlings, suggesting that it affects wilt indirectly by changing the soil microflora. Both in the glasshouse and the field chitin greatly increased the numbers of actinomycetes, fungi and bacteria in the rhizosphere, whereas it decreased the population of P. oxysporum f. pisi. Similar microbial changes occurred in ‘wilt‐sick’ soil without plants, indicating that root exudates and debris intensified rather than determined these changes.

Micro‐organisms isolated from the rhizosphere soil treated with chitin were more antagonistic towards F. oxysporum f. pisi race I, and the sterile rhizosphere extracts were also more inhibitory to its spore germination in vitro, than were those from the rhizosphere in soil without chitin. Chitin therefore seems to diminish wilt by stimulating micro‐organisms that antagonize and/or lyse the pathogen.
The growth of Botrytis fabae and B. cinerea into leaves of bean (Vicia faba L.)
Authors: PURKAYASTHA R. P. , DEVERALL B. J.
Published: February 2008

The nature of the reactions underlying the success of Botrytis fabae and the failure of B. cinerea to colonize the leaves of bean (Vicia faba L.) have been studied.

Damage to or removal of cuticle before inoculation failed to enable B. cinerea to cause spreading lesions. Nutrients including those which support good growth in vitro failed to stimulate B. cinerea to spread through leaves.

The germination of spores of B. cinerea in water was more rapid and complete than of B. fabae on both glass and leaf surfaces. B. cinerea grew more rapidly than B. fabae in nutrient media, but germ tubes of B. fabae grew at a higher constant rate than those of B. cinerea in water drops on glass. In water drops on leaves, germ tubes of B. fabae grew at a constant rate but those of B. cinerea slowed after 8 hr. and then grew little more. Germ tubes of B. fabae were the same length after 24 hr. both over and away from lesions, but those of B. cinerea were markedly shorter over lesions than away from them at this time.

Similar observations on pathogenicity and relative growth of the two fungi were made on six bean varieties.
Bacterial canker of stone‐fruits
Authors: CROSSE J. E.
Published: February 2008

On two different plots of cherry trees, the bacterial canker organism (Pseudomonas mors‐prunorum) outnumbered all other gram‐negative bacteria on the leaf surfaces in the approximate proportions of 4:1 and 3:1, respectively. The saprophytic flora was dominated by an organism having affinities with Erwinia spp. In mixed‐infection experiments this was shown to be capable of reducing the incidence and/or severity of leaf‐scar infection. The inhibitory activity of the saprophyte in different experiments was related to the amount of disease, and its general effect was similar to that which would have been expected from reducing the concentration of the pathogen in the inocula. Spraying bacterial suspensions on to trees substantially increased populations of the saprophyte, but these rapidly decayed and the natural equilibrium on the leaf surfaces was re‐established within a few days.
Studies on induced mutants of Corynebacterium fascians and on their pathogenicity in comparison with that of ‘natural’ strains
Authors: JACOBS S. E. , HABISH H. A. , DADD A. H.
Published: February 2008

Colony‐type, non‐pigmented and nutritional (auxotrophic) mutants of Corynebacterium fascians were isolated after ultraviolet irradiation of a highly virulent strain. The auxotrophs had single requirements for glycine, aspartic acid, arginine, methionine, creatine or adenine and the amount of their growth in a minimal medium adequate for the parent strain was controlled by the amount of the respective nutrients added.

Preliminary results indicated that the pathways by which C. fascians synthesises the substances (with the exception of methionine) required by the mutants were those already known for other micro‐organisms.

The induced auxotrophic mutants were examined, in comparison with ‘natural’ or wild strains, for ability to infect sweet pea seedlings and to grow in the environment provided by the host. The mutants were avirulent or weakly virulent unless the specific nutrient was added, and this was correlated with the amount of growth made by the mutants in an aqueous extract of the host tissue. Addition of the specific nutrient improved the growth of the mutant, thus suggesting that avirulence was due, at least in part, to the inability of the pathogen to grow sufficiently in the host environment.
The biology of Sclerotinia trifoliorum Erikss. and other species of sclerotium ‐forming fungi
Authors: WILLIAMS G. H. , WESTERN J. H.
Published: February 2008

In studies of the behaviour of sclerotia of Sclerotinia trifoliorum, S. sclerotiorum, Sclerotium delphinii and S. rolfsii it was established that S. trifoliorum and S. sclerotiorum formed apothecia in the field, S. sclerotiorum mainly in spring and S. trifoliorum almost exclusively in autumn. Apothecia were formed from sclerotia down to 2 in. in the soil, the number diminishing with increasing depth. At 6 in., sclerotia developed apothecial stipes up to 21/2 in. long: this limitation was not due to exhaustion of the food reserves of the sclerotia.

In S. trifoliorum, apothecial formation was abundant in August, then steadily declined, and ceased in November. Broad red clover was exceptional in stimulating the initial flush in both S. trifoliorum and S. sclerotiorum, but very few apothecia formed subsequently.

Mycelial growth from sclerotia of S. trifoliorum and S. sclerotiorum was much sparser, even in sterilized soil, than that from sclerotia of Sclerotium delphinii and S. rolfsii.
Mercury residues in apples from trees receiving organomercurial fungicide in the previous autumn and winter
Authors: TEW R. P. , SILLIBOURNE JOAN M.
Published: February 2008

Mercury residues have been measured in apples from trees receiving experimental applications of phenylmercury chloride in the previous autumn and/or in the dormant season. In the absence of organomercurial sprays in the succeeding summer, mercury could not be found in the fruit at harvest. Even when post‐harvest or dormancy applications preceded conventional summer schedules of an organomercurial fungicide, residues of mercury at harvest were not increased.
Studies on plant cuticle
Authors: SILVA FERNANDES A. M. S.
Published: February 2008

Surfaces of apple, banana, blackcurrant, broad bean, cabbage, coffee, hydrangea, pea, rose, Eucalyptus, Exochordia and Rhus leaves and apple fruit are classified by a standardized wetting test into those that are water‐repellent, those that are easily wetted and those over which water spreads without wetting. The affinity of a surface for water is influenced by the amount and chemical composition and especially by the physical configuration of the wax present on the surface.
Effect of CCC (chlorocholine chloride) on growth and yield of spring wheat in the field
Authors: HUMPHRIES E. C. , WELBANK P. J. , WITTS K. J.
Published: February 2008

Spring wheat, var. ‘Phoebus’, drilled at 11/2 times the usual rate and grown with three rates of nitrogen was treated with 2.5 or 5 lb. CCC per acre at the sixth‐leaf stage. At maturity, the height of treated plants was only 60% of that of untreated plants, but the percentage shortening was less as nitrogen increased. Although untreated plants did not lodge, CCC increased mean grain yield by 5% by increasing the number of ears and number of grains per ear. Grain weight per ear and thousand‐grain weight were decreased by CCC. The explanation of the increase in shoot number by CCC is not known, but possibly less light was intercepted by the shorter plants, so that later‐formed shoots survived to produce ears.

CCC decreased assimilatory area by shortening stems and hence leaf sheath area; lamina area was little affected. It delayed ear emergence by up to 8 days, Leaf‐area index was decreased by CCC and as it increased, net assimilation rate decreased. CCC did not affect nitrogen uptake per unit area of land but it increased nitrogen as percentage of dry matter because it decreased dry‐matter yields.
The infectivity of soils containing Phytophthora infestans
Authors: LACEY J.
Published: February 2008

Infectivity of soil was measured by incubating samples on potato tuber slices during and after outbreaks of potato blight in three years. Surface soil was always more infective than deeper soil, the most infective surface soil containing the equivalent of 2100 sporangia of P. infestans per ml. Infectivity usually diminished rapidly with increasing depth, and only occasionally did infectivity below 2 in. exceed the equivalent of 100 sporangia per ml. Exceptionally large infectivity was once found at all depths sampled after heavy rain, but rain did not consistently affect infectivity. The surface soil remained infective for at least 32 days after the haulm was killed with acid, but the concentration of viable spores declined to a small value during the first week after treatment. In the laboratory infectivity persisted for 11 weeks after sporangia were mixed with unsterilized soil originally with a moisture content of 20%. P. infestans mycelium grew only in sterilized soils, perhaps because some soil micro‐organisms inhibit its growth, and others (e.g. Trichoderma viride) parasitize it or lyse it (e.g. by Rhizoctonia solani). The three soils tested all contained substances that inhibit the germination of sporangia.
Infection of hop rootstocks by downy mildew Pseudoperonospora humuli (Miy. & Tak.) Wilson and its control by early‐season dusts
Authors: COLEY‐SMITH J. R.
Published: February 2008

Infection of hop rootstocks by Pseudoperonospora humuli has been shown to occur as a result of inoculation of the tips of shoots 15 cm. or less in length. No rootstock infection developed when shoots were more than 17.5 cm. long at the time of inoculation. Infection via the base of shoots can occur at any time during the growing season and is thought to be the main source of rootstock disease under natural conditions. The importance of direct infection of hop rootstocks by zoospores of P. humuli, which occurs readily under laboratory conditions, is not known.

Application of Bordeaux (6.5% Cu) and captan (15% a.i.) dusts to the crowns and shoot bases of field plants retarded development of rootstock disease and shoot infection (basal spikes) in originally disease‐free plantings of Golding hops.
Investigations on fungicides
Authors: HEYNS A. J. , CARTER G. A. , ROTHWELL K. , WAIN R. L.
Published: February 2008

The fungicidal properties of thirty‐three N‐substituted S‐esters derived from dithiocarbamic acid were examined. Several compounds inhibited the germination of spores of Botrytis fabae in vitro at concentrations below 100 p.p.m., but activity against Erysiphe graminis was considerably lower. In greenhouse tests the compounds were not effective against B. fabae when sprayed on broad bean seedlings but several gave more than 80% reduction of mildew infection when sprayed on wheat seedlings. Some compounds also showed a marked eradicant action against wheat mildew.

The effect of pH, plant sap and amino acids upon their fungitoxicity was also studied and the degree of activity shown by the compounds is discussed in relation to these and other factors.
The respiration of leaves showing necrotic local lesions following infection by tobacco mosaic virus
Authors: SUNDERLAND D. W. , MERRETT M. J.
Published: February 2008

At 25°C. the respiration rate of leaves ofNicotiana tabacum L. var. Xanthi infected with tobacco mosaic virus increased before the appearance of local lesions. The increase was directly proportional to lesion number at low, but not at higher, lesion densities. With temperatures at which the infected leaf showed necrotic lesions the difference in respiration rates between healthy and infected leaves was greater than at 35°C., at which temperature infected leaves do not develop necrotic lesions. The concentration of 2,4‐dinitrophenol (DNP) that gave maximum stimulation of the respiration of the healthy leaf was 10‐5M, but even this respiration rate was less than that of the infected leaf showing local lesions. DNP had no effect on the respiration of the infected leaf showing a dense lesion cover. At 35°C., DNP increased the respiration rate of infected leaves and the maximum respiration rates for healthy and infected leaves in the presence of DNP were similar.