bluuebunny/crossref_metadata_2025 huggingface dataset:
The symptoms and causal agents of early‐dying disease (Verticillium wilt) of potatoes
Authors: ISAAC IVOR , HARRISON J. A. C.
Published: February 2008

The only characteristic symptom produced by Verticillium albo‐atrum and V. dahliae in infected potato plants is unilateral chlorosis and necrosis: this was not shown until the approach of host maturity, and was distinguishable from symptoms of natural senescence only in its slightly earlier expression.

Of six species of Verticillium tested against potato (King Edward), V. albo‐atrum, V. dahliae, V. nigrescens and V. nubilum were pathogenic (all produced ‘wilt’ symptoms and relative virulence was in that decreasing order) but V. tricorpus and V. lateritium did not induce disease. Isolates of V. albo‐atrum and V. dahliae, obtained from a number of other host plants, were also pathogenic to potato.

Possible reasons are given for the fewness of records of ‘Early dying’ disease (Verticillium wilt) of potatoes in the field.
Sclerotinia fructigena infection and chlorogenic acid content in relation to antifungal compounds in apple fruits
Authors: FAWCETT C. H. , SPENCER D. M.
Published: February 2008

Several organic acids, known to occur in many apple varieties, were shown to be present in the juice of the variety Edward VII. When these were supplied separately to the brown rot pathogen, Sclerotinia fructigena, growing in culture, chlorogenic acid and quinic acid were both readily converted to compounds of higher antifungal activity, one of which was 4‐hydroxybenzoic acid. The chlorogenic acid content of concentrated healthy fruit juice was ˜6 mg/g, whereas the corresponding syrup from diseased fruit contained only ˜2 mg/g. The possible significance of this metabolism of chlorogenic acid by the fungus is discussed.
Studies on plant growth‐regulating substances XXVI. Isatic and anthranilic acids
Authors: JAMES C. S. , WAIN R. L.
Published: February 2008

The plant growth‐regulating activities of isatic acid and twenty‐six of its derivatives, together with the twenty‐seven corresponding anthranilic acids, have been assessed in the wheat cylinder, the pea segment and the pea curvature tests. Activity was sustained by substitution in the 4‐ and 5‐positions of isatic acid but decreased by substitution in the 3‐ and 6‐positions. In the anthranilic acid series, the parent acid was inactive but the introduction of a large grouping (bromine or iodine) into the 5‐position conferred activity. The 3,6‐ and 5,6‐dichloro and the 3,6‐dibromo acids were also active; compounds substituted in the 4‐position to the carboxyl group or disubstituted in the 3,5‐positions, were, as expected, inactive.

In metabolism experiments on wheat and pea tissues with isatic and 5‐chloroisatic acids the corresponding anthranilic acid was formed, together with an unidentified non‐acidic metabolite in each case. There was no evidence that the growth regulating activity of isatic acids was related to this breakdown and it is concluded that the acids possess activity per se. The results are briefly discussed in terms of recent theories relating chemical structure to plant growth‐regulating activity.
The relationship between aphid infestations and oviposition by aphidophagous Syrphidae (Diptera)
Authors: CHANDLER A. E. F.
Published: February 2008

Oviposition by aphidophagous Syrphidae varies with the size of aphid infestations and different syrphid species have different optimum aphid population sizes for oviposition.

In one experiment using potted brussels sprout plants infested with Brevicoryne brassicae L., Platycheirus manicatus (Meig.) preferred about 100 aphids per plant, P. scutatus (Meig.) about 1000 aphids per plant and Syrphus ribesii (L.) about 2000 aphids per plant. These preferences were less clear in certain Platycheirus species (e.g. P. peltatus (Meig.)), than in Syrphus species (e.g. S. luniger Meig.).

Once a plant has been selected for oviposition there may still be selection of suitable colonies on that plant. For a given aphid population, S. luniger preferred a small number of large aggregates to a larger number of smaller ones, whereas S. balteatus (Deg.) preferred the opposite.

The tendency of the different species to select aphid populations of different sizes and distributions is likely to decrease interspecific competition.
Some factors influencing the occurrence and site of oviposition by aphidophagous Syrphidae (Diptera)
Authors: CHANDLER A. E. F.
Published: February 2008

Syrphids were not deterred from ovipositing on suitable plants by the presence of other syrphid eggs, larvae or larval gut contents. Heavy infestations of Aphis fabae Scop, on bean plants (Viciafaba L.) induced Platycheirus manicatus (Meig.) to lay preferentially on neighbouring uninfested plants. Such behaviour was not found for Syrphus species. Nor did flowers, a source of adult food, stimulate oviposition nearby.

The site of oviposition in relation to Brevicoryne brassicae L. on brussels sprouts (Brassicae oleracea gemnifera L.) varied markedly according to species: in similar conditions Syrphus luniger Meig. laid over 50% of its eggs touching aphids and less than 1% on uninfested plants, whereas P. manicatus laid less than 5% touching aphids and over 50% on uninfested plants. Most eggs were laid close to the edge of the leaf, especially by Platycheirus species, e.g. P. scutatus Meig. which laid over 90% within 5 mm of the edge of the leaf.
Dieldrin‐resistant cabbage root fly in England
Authors: GOSTICK K. G. , BAKER PATRICIA M.
Published: February 2008

The existence of dieldrin resistance in Erioischia brassicae has been investigated in the main areas in England and Wales where brassicas are grown for human consumption. Dieldrin‐susceptible and dieldrin‐resistant flies were collected and bred as separate strains in the laboratory. In toxicity tests adult flies were treated with topically applied doses of insecticide in microdrops of cellosolve, and larvae were dipped in solutions of insecticide in 70% acetone and 30% water. Adults of the laboratory resistant strain showed a high level of resistance to dieldrin and aldrin and a lower level of resistance to γ‐BHC. There was no cross‐resistance with chlorfenvinphos or diazinon. Larvae of the resistant strain were shown to be resistant to dieldrin.

Dieldrin resistance has been found in four areas in southern England, but not in a fifth major area, and resistant flies did not increase as rapidly in some areas as others. Sufficient migration of flies appeared to take place to produce similar percentages of resistant flies over areas of several square miles, but considerable differences were found in fly populations about 10 miles apart. It is suggested that the speed of development of insecticide resistance is affected by the proportion of brassica crops which are treated in an area, the amounts of insecticide applied to individual crops, and hence the insecticidal pressure applied to the E. brassicae population.
A biological assay technique for the assessment and comparison of systemic insecticide residues
Authors: GALLEY D. J.
Published: February 2008

A technique is described using mortality of aphids on excised leaf samples to assess residual systemic insecticides within the leaf or on its surface. Residues in crops or soil can also be assessed by keeping aphids on leaf samples treated with solvent extracts of contaminated material. Little or no pre‐treatment for the removal of potentially interfering materials co‐extracted from the crop is required. Comparison of mortalities caused by unknown residues with mortalities caused by known amounts of insecticide enables the technique to be used quantitatively. The sensitivity of the technique varies with the toxicity of the compound being assayed. With most of the insecticides tested, extract solutions down to about 10 ppm may be assessed directly; weaker solutions must first be concentrated.
Laboratory studies on the acute contact and oral toxicities of insecticides to honeybees
Authors: STEVENSON J. H.
Published: February 2008

Standard procedures for determining acute oral and contact toxicities of insecticides to worker honeybees were developed and used to find the median lethal doses (LD50) of twenty‐one compounds. The test procedures can be simplified to give less precise results and can be applied with little modification to other species of bee.
Studies on plant growth‐regulating substances XXVII. The growth‐regulating activity and metabolism of 2,4‐dichlorophenoxyethylamine and related compounds in higher plants
Authors: NASH R. J. , SMITH T. A. , WAIN R. L.
Published: February 2008

2‐(2,4‐Dichlorophenoxy)ethylamine (2,4‐D ethylamine) was converted to 2,4‐dichlorophenoxyacetaldehyde (2,4‐D acetaldehyde) by extracts of pea cotyledons. The 2,4‐D acetaldehyde was further converted to 2,4‐dichloro‐phenol and 2,4‐dichlorophenoxyacetic acid (2,4‐D). Under the same conditions, 2‐(2,6‐dichlorophenoxy)ethylamine was converted to 2,6‐dichloro‐phenoxyacetaldehyde and 2,6‐dichlorophenol, although at a relatively slow rate.

In pea stem segments and wheat coleoptiles the main products of 2,4‐D ethylamine metabolism were 2,4‐dichlorophenol, 2,4‐D acetaldehyde and 2,4‐D. In comparison with the wheat coleoptiles, larger amounts of these products were found in the pea stem segments. Metabolism of 2,4‐D acetaldehyde gave 2‐(2,4‐dichlorophenoxy)ethanol (2,4‐D ethanol) and 2,4‐D in both pea and wheat tissues.

Pretreatment with the amine oxidase inhibitor, 2‐hydroxyethylhydrazine (HEH) completely prevented the extension of pea stem segments and substantially prevented the extension of wheat coleoptiles on subsequent treatment with 2,4‐D ethylamine. No such protection was found against 2,4‐D acetaldehyde or 2,4‐D after pretreating the tissues with HEH.

In pea, radish, and tomato plants, epinasty resulted from treatment with 2,4‐D ethylamine, 2,4‐D acetaldehyde and 2,4‐D. Prior treatment with HEH prevented the epinasty due to the 2,4‐D ethylamine, but no protection was given by HEH against 2,4‐D acetaldehyde or 2,4‐D.
Laboratory methods for assessing the toxicity of contact poisons to slugs
Authors: HENDERSON I. F.
Published: February 2008

Two techniques for comparing the activity of different contact poisons to slugs in controlled conditions were used to measure the relative toxicities of five substances. A laboratory immersion test rated their median lethal concentrations as follows: ioxynil 8·3 ppm, sodium pentachlorophenate 22·0 ppm, copper sulphate 68·1–75·3 ppm, acetaldehyde 4822·0 ppm. Metaldehyde gave inconsistent results with this method but, using a dry‐contact method, metaldehyde (42370 ppm) was much less toxic than copper sulphate (2027 ppm). The materials giving practical control in the field were not the most toxic of those tested.
The toxicity and sublethal effects of p,p‘‐DDT and dieldrin to Aglais urticae (L.) (Lepidoptera: Nymphalidae) and Chorthippus brunneus (Thunberg) (Saltatoria: Acrididae)
Authors: MORIARTY F.
Published: February 2008

Single topical doses of pure p,p'‐DDT and dieldrin (HEOD) were given to the last larval instars of Chorthippus brunneus and Aglais urticae bred under standardized conditions. The symptoms of acute toxicity followed the same pattern in all four insect‐insecticide combinations, and there was a clear inverse correlation between the toxicity of absorbed insecticide and concentration of total lipid when dosed, both being dependent on age. It is probable that developmental changes in concentration of total lipid cause changes in resistance to the lipophilic and hydrophobic organochlorine insecticides. These results illustrate the importance of using the amount of insecticide absorbed rather than the amount applied for the interpretation of data. Unabsorbed insecticide was estimated by methanol rinses; there was some evidence that these remove a small proportion of absorbed insecticide from A. urticae, but not from C. brunneus.

Sublethal effects tend to occur at times of lipid mobilization. There was considerable correlation between insecticide persistence and the occurrence of sublethal effects. Both species convert DDT to DDE readily, although only A. urticae retains DDE for long. No obvious effects were detected in C. brunneus. The only effect in A. urticae was retarded pupation when a large dose was applied fairly near the time of pupation. Dieldrin was more toxic and persistent, and caused latent toxicity, deformation of adults, sterility, and hyperactivity of adults in A. urticae, although there were no apparent effects on C. brunneus except for a possible decrease in the time to moult. Neither insecticide affected water uptake in C. brunneus eggs, and development continued normally up to hatch. The hatched nymphs were unaffected by DDT, most of which was in the egg membranes, and the nymphs rapidly metabolized the rest to DDE. Dieldrin did kill nymphs at eclosion. There was no evidence of effects on the genetic constitution of future generations, but the survival and reproductive abilities of individuals can obviously be affected.

I conclude, from two measures of the amount of insecticide acquired by A. urticae in the field, and from the amount required to produce sublethal effects, that A. urticae is probably, with present levels of contamination, unaffected by DDT or dieldrin outside sprayed areas, but more information is needed on other possible effects, and on amounts found in wild specimens. I discuss how far this conclusion applies to other insect species.
White rust of chrysanthemums
Authors: FIRMAN I. D. , MARTIN P. H.
Published: February 2008

Teleutospores of Puccinia horiana Henn. germinate and discharge sporidia between 4 and 23 °C. At the optimum temperature of 17 °C sporidia discharge starts within 3 h. Maximum germination of the sporidia takes place within 2·5 h between o and 30 °C, there being no clear optimum. High humidity and a film of moisture appear to be necessary for germination of both teleutospores and sporidia. Sporidia can penetrate either leaf surface of chrysanthemum to cause infection between 4 and 24 1°C and within the optimum temperature range, 17–24 °C, effectively penetrate within 2 h. The sporidia are very sensitive to desiccation at below 90 % relative humidity.

Methods are described, using leaf discs and whole plants, for screening chrysanthemum cultivars for susceptibility to white rust. Cultivars were placed in five classes ranging from susceptible to immune. Leaf discs of immune cultivars can be distinguished within 30 h by a brown discolouration at the point of inoculation. The early stages of development of the fungus in susceptible, resistant and immune hosts are described. The incubation period in susceptible plants is normally 7–10 days, teleutospores being formed a few days later. Leaves become less susceptible with age but the oldest leaves on 5‐month‐old plants could still be infected. The maximum survival time of teleutospores in the sori on detached leaves was 8 weeks but was considerably less under moist conditions or buried in soil. Low doses of a mancozeb with zineb fungicide controlled infection by preventing penetration rather than by inhibiting sporidial germination.
Studies on Sphacelia sorghi McRae, an ergot of Sorghum vulgare Pers.
Authors: MANTLE P. G.
Published: February 2008

The constituent ergoline alkaloids produced in vitro by a Nigerian strain of Sphacelia sorghi have been identified as dihydroergosine, festuclavine, pyroclavine, dihydroelymoclavine, and chanoclavine. The same alkaloids were present in both the sphacelial stage and the sclerotia when S. sorghi parasitized florets of Sorghum vulgare. The Nigerian fungus appears to be quite different from certain oriental collections bearing the same name, and although forming stromatal initials, failed to develop the sexual stage. Mice successfully raised litters and showed no adverse response when fed on diets containing up to 50% of the ergot sclerotia. The ergot had also no effect on early pregnancy. Some of the alkaloid was excreted in the faeces, but, as injected alkaloid was also shown to be excreted in the faeces, this could have represented alkaloid which had been absorbed from the ingested sclerotia and re‐excreted via the bile.
Studies on the survival of Mycosphaerella pinodes and Ascochyta pisi
Authors: DICKINSON C. H. , SHERIDAN J. J.
Published: February 2008

Laboratory and field experiments on two pea‐pod and leaf‐spot pathogens, Mycosphaerella pinodes and Ascochyta pisi, have indicated that the former species may survive overwinter in soil whether introduced as pycnidiospores, mycelium, chlamydospores or sclerotia. The survival of pycnidiospores appears to be due at least in part to their transformation into chlamydospores in the soil. A. pisi was much less successful in soil; the mycelium inoculum survived, somewhat sporadically, and spore viability was reduced, while the total number of spores declined markedly. Investigations on the competitive saprophytic ability of these pathogens showed that by the agar plate method M. pinodes could be classed as a moderately successful saprophyte, though the Butler and Park methods indicated only intermediate and poor success respectively. A. pisi was adjudged a poor saprophyte by all three methods. Saprophytic growth and survival in soil of both fungi was generally better at 2 °C than at 15 °C.
Induced tolerance of Sclerotium cepivorum to antibiotics in the presence of onion exudates
Authors: Keyworth W. G. , Milne L. J. R.
Published: February 2008

The onion white rot pathogen Sclerotium cepivorum was cultured on agar media containing 2% malt extract and one of the antifungal antibiotics, endomycin, griseofulvin, venturicidin and cycloheximide at concentrations that reduced but did not prevent growth of mycelium. When onion seeds or agar discs impregnated with diffusates from onion bulbs were placed on the antibiotic media, radial growth of the fungus was greatly increased, and there was a profuse development of aerial mycelium. Gaseous diffusates from onion tissue and from impregnated agar discs were also effective. On the antibiotic media, tomato, cabbage and radish seeds did not stimulate the growth of S. cepivorum and the onion exudates did not stimulate the growth of four other fungi. This and other evidence is considered to show that the stimulation of growth of S. cepivorum was not caused by any direct effect on the antibiotics but by a tolerance of the fungus to them, which was specifically induced by an exudate from its host plant. The phenomenon may be related to the reported reversal by onion extracts of the inhibitory effects of soil mycostasis on germination of sclerotia of the fungus.
Assessment of the damage caused to potatoes by potato cyst eelworm, Heterodera rostochiensis Woll
Authors: BROWN E. B.
Published: February 2008

Thirty field trials were carried out from 1960 to 1967, mainly on peat and silt soils in the eastern counties of England, to study the relationship between potato yield and numbers of H. rostochiensis. The population range of most interest to advisers (0–60 full cysts/100 g (0–150 eggs/g)) was encountered by chance fairly frequently. The relationship between yield and initial eelworm densities over this range could be expressed equally well untransformed or transformed (using square root transformation for cyst counts and log. transformation for egg counts). Sigmoid curves could not often be fitted to the graphs of yield against log. egg count because densities large or small enough were not often encountered and small numbers cannot be estimated with sufficient accuracy.

Assuming straight‐line regressions of yield on untransformed eelworm densities certain generalizations can be made. The slopes vary somewhat, but on average losses are 1·2 tons/acre per ten full cysts/100 g and 0·85 tons/acre per twenty eggs/g. Linear regressions tend to be parallel over a large range of potential yields which means that yield loss is independent of potential yield.

In five trials there was some evidence that the yield had reached a minimum varying between 5 and 10 tons/acre when eelworm populations were very dense. In two trials, estimates of maximum and minimum yield were obtained. Both gave the difference (maximum loss) as 7 tons/acre and the ratio of minimum to maximum as 0·50 and 0·44 respectively.

Yield losses were often great without obvious symptoms appearing in the haulm.
Epidemiology of cocksfoot mottle virus
Authors: UPSTONE M. E.
Published: February 2008

Cocksfoot mottle virus (CFMV) was found to be widespread in cocksfoot seed crops in the East Midlands in the third harvest year and once present in the crop spread rapidly. Pot experiments with single cocksfoot plants showed that autumn infection with CFMV resulted in a significant reduction in the number of flowering tillers and weight and size of seed produced the following year.

The spread of CFMV in experimental cocksfoot leys was studied; leys cut for conservation showed more infection than leys grazed by sheep, and increasing nitrogen application resulted in higher disease incidence. The disease increased rapidly in conserved leys in 1967 and its spread was associated with cutting by a forage harvester after the virus had been introduced into the crop in the autumn, possibly by the vector Lema melanopa. Animal grazing and cutting implements seemed to be more important agencies in disease spread than the vector.
Studies on the bacterial diseases of Sudan crops
Authors: SABET K. A. , ISHAG FARIDA
Published: February 2008

Xanthomonas phaseoli survived for more than 18 months in press‐dried dolichos bean leaves kept in the laboratory. Survival of the organism in pure culture, or in leaf trash mixed with the soil, depends on soil moisture, being longest in air‐dried and shortest in water‐saturated soil. In completely water‐saturated, or in completely air‐dry soil, no effect of soil autoclaving is observed. In moistened soil survival is longer in autoclaved than in untreated soil. In the absence of demonstrable phage activity, disappearance of the organism in water‐saturated soil is attributed to prevailing anaerobic conditions, and in moistened soil to the action of competitive saprophytes. In air‐dry soil the organism is preserved by drying.

The bacteria reach the seed, via the placenta, when young pods, less than 2 cm long, become infected by artificial inoculation: they do not invade the vascular tissues. Survival of the bacteria in the seed is considered of a relatively little importance in practice.

Seedling infection is characterized by elongated brown lesions on the veins of the simple and first and second trifoliate leaves; those parts of the lamina dependent on affected veins become chlorotic and flaccid. Vein lesions show the pathogen in the vascular bundles, which exhibit no tissue differentiation.

A strain of X. phaseoli from Vigna radiata (weed plant) also infects dolichos bean. Its minimal infective dose on Dolichos is considerably higher than that of the dolichos bean strain.

The dolichos bean disease can be transmitted by heavy infestation of the whitefly Bemisia tabaci.
The effect of fungicidal treatments on sporulating capacity in relation to the control of coffee berry disease
Authors: NUTMAN F. J. , ROBERTS F. M.
Published: February 2008

The capacity of the maturing wood of the branches of Coffea arabica to produce conidia of Colletotrichum coffeanum Noack, the causal agent of coffee berry disease, is profoundly affected by fungicidal treatments. The effect differs according to the epidemiology of the disease. When the main source of inoculum is from the wood, the reduction in the sporulating capacity persists throughout the crop‐season, and good control of the disease results. When the main source of inoculum is from diseased berries, reinfection of the branches takes place, the sporulating capacity of sprayed branches rises above that of unsprayed ones, and there is indifferent or no control. Evidence from field trials suggests that the correct timing of early season spray schedules may be related to the part of the annual rhythm of sporulating capacity at which they are applied. As this rhythm is determined by rainfall, and varies from year to year and from place to place, the correct time for the start of a schedule should be predictable from meteorological data.
Fungicidal activity and chemical constitution
Authors: CLIFFORD D. R. , DEACON A. C. , HOLGATE MARGARET E.
Published: February 2008

Structure/activity relationships for members of five homologous 4‐(1‐substituted alkyl)‐2,6‐dinitrophenols and apple mildew are discussed with special reference to their hydrophobic bonding constants π. It is suggested that π values may be of use in predicting potential anti‐mildew fungicides with similar modes of action to those of the substances studied.
Seed treatments with Vitavax for the control of loose smut of wheat and barley
Authors: MAUDE R. B. , SHURING CATRIONA G.
Published: February 2008

Seed dressings with Vitavax—75 % w.p.—eliminated Ustilago nuda in spring barley seeds and greatly reduced infection due to U. tritici in winter wheat. Emergence and yield of these crops were not adversely affected. Seed soak treatments including 0·2 % aqueous Vitavax for 6 h at 30 °C (wheat and barley), 0·2% thiram for 24 h at 30 °C (barley) and 0·2% Vitavax for 1 h at 30 °C (barley) also rid the seeds of infection. In other tests with barley 2 h soaks in 0·2 % aqueous suspensions of Vitavax at 30 °C gave equivalent control to 12 h soaks in 0·2% thiram at 30 °C.
An investigation of the toxicity of insecticides to birds' eggs using the egg‐injection technique
Authors: DUNACHIE J. F. , FLETCHER W. W.
Published: February 2008

Twenty‐five insecticides have been tested for their toxicity to hen embryos at various concentrations, using an egg‐injection technique. Of the two major groups, the organophosphorus compounds are much more toxic than the organochlorine. Most organophosphorus compounds lower the hatch rate and cause teratogenic effects at 100 ppm. Most organochlorines do not harm the embryo at high dosages (up to 500 ppm), with notable exceptions to this among the cyclodienes. However, starvation of the hatched chicks suggests that the majority of organochlorine compounds can kill at this stage, though fed chicks survive. The solvent used affected toxicity; in general, insecticides are more toxic to the embryo when dissolved in corn oil than when dissolved in acetone. If these findings can be applied to wild birds, it can be assumed that the vast majority of insecticides are harmless to birds' eggs. They are either not toxic in the concentrations so far found in this country, or else unlikely to pass through the mother bird to the egg.
Aggressive behaviour in related and unrelated wild house mice (Mus musculus L.)
Authors: ROWE F. P. , REDFERN R.
Published: February 2008

Aggressive behaviour was observed to be rare in small family groups of confined wild house mice, Mus musculus L. Unrelated mice were attacked when they were introduced to a family group and in their presence intra‐family aggressive behaviour increased. When two family groups of mice were allowed to meet there were frequent aggressive encounters between unrelated animals and the two groups remained separate.

Resident mice were found to be aggressive towards males and females individually isolated and returned to their own family after 2 or 3 weeks absence but not after 1 week. The possibility is discussed that in wild mice odour discrimination influences the dispersal and build‐up of free‐living populations.
The potential of Chrysopa carnea as a biological control agent of Myzus persicae on glasshouse chrysanthemums
Authors: SCOPES N. E. A.
Published: February 2008

Larvae of C. carnea lived for 13‐4 days at 21·1°C and consumed an average of 385 second‐instar Myzus persicae or 425 Aphis gossypii. At 15·5°C the larval lifespan was 29·5 days though the consumption of M. persicae was hardly affected.

M. persicae developing on glasshouse chrysanthemum plants were eliminated by the introduction of 1‐day‐old larvae at aphid: chrysopid ratios up to 50:1; third‐instar larvae achieved control at a ratio of 200:1. At very low aphid densities control was less effective.

Control by C. carnea of aphid populations developing on glasshouse chrysanthemums can be predicted mathematically.
Build‐up of tomato brown root rot caused by Pyrenochaeta lycopersici Schneider and Gerlach
Authors: LAST F. T. , EBBEN M. H. , HOARE R. C. , Turner E. A. , Carter A. R.
Published: February 2008

The incidence in unheated glasshouses of tomato brown root rot (BRR) was recorded on five successive crops starting with the first ever grown on the experimental site. In the protected environment the changes followed a pattern that was defined mathematically, the regression linking angular or logit transforms of per cent BRR, observed at different intervals after planting, accounting for c. 72% of the variation. Rates of build‐up, seemingly related to initial amounts of inocula, increased in successive seasons, there being more BRR in the fifth season than in the first. Four per cent BRR recorded 5 weeks after planting increased threefold during the next 3 months to 12 %, but in later years, when amounts of early‐season infection were doubled to 8%, the incidence of root rot subsequently increased five times.

Tomato roots colonized by Pyrenochaeta lycopersici either brown and rot or become corky. The proportion of end‐of‐season BRR attributable to corkiness increased from the first to fifth seasons.

The monthly increments of fruit yield were inversely proportional to the incidence of BRR.
Growth and wilt (Verticillium dahliae) development in strawberry cultivars over a transition between two soil series
Authors: TALBOYS P. W. , BENNETT MARGERY
Published: February 2008

On a site infested with V. dahliae the incidence of wilt was low consistently in strawberry cvs Talisman and Redgauntlet, high in Merton Herald and Gorella, and very high in Merton Ruby, Cambridge Vigour, Prizewinner, Templar and Crusader.

Changes in mean volume per plant for the whole population of each cultivar were closely related to disease incidence and therefore differed between high‐resistance and low‐resistance cultivars.

Height and spread measurements of diseased and symptomless plants in certain cultivars showed differences in the severity of the effect of the pathogen on growth that were not closely related to wilt incidence.

Gradients of disease incidence and plant growth in 1966 and 1967 were associated with a transition from one soil series to another. Review of two earlier experiments on the same site revealed a similar gradient of disease incidence in 1963‐64, but a reversed gradient in 1960‐62. Variations related to soil conditions were smaller in the earlier experiments than in 1966‐67.
Tomato leaf mould: its assessment and effects on yield
Authors: SMITH PAULINE M. , LAST F. T. , KEMPTON R. J. , GISBORNE J. H.
Published: February 2008

When the natural incidence of Cladosporium fulvum Cooke, occurring at a relatively late stage of cropping, was controlled with fungicides, comparisons with unsprayed control plants showed that there was an interval of c. 6 weeks between the incidence of severe infection, when the fungus was colonizing at least 50 % of the host's leaf area, and fruit yield decreases.

Eye estimates made on separate leaves usually over‐estimated the percentage of infection. Correction factors were derived from the regression of eye estimates on infected areas calculated from leaf tracings. Whole‐plant infection indices were obtained by averaging corrected values of percentage infection separately assessed on leaves immediately above each fruit truss.

Although dichlofluanid and tank‐mixed zineb decreased the incidence of C. fulvum more than captan sprays, tomato yields (including green fruit) were increased similarly by all three fungicides from 2·99 to an average of 3·51 kg/plant during c. 3 months' picking. Decreasing the intervals between successive sprays from 21 to 7 days greatly decreased leaf mould infection but did not significantly affect yields. Restricting applications to plant tops (namely foliage from the fourth‐youngest truss to the mainstem apex) gave yield benefits equal to those gained from sprays applied to whole plants.
Effects of nitrogen and glucose on saprophytic survival of Ophiobolus graminis in buried straw
Authors: SCOTT P. R.
Published: February 2008

Calcium nitrate prolonged the saprophytic survival of Ophiobolus graminis (Sacc.) Sacc. in artificially colonized straws buried in soil in the laboratory, whether supplied to the soil (at 12·5 or 100 mg nitrogen/100 g soil) or to the straws before colonization (at 0·5 or 1·0 g nitrogen/100 g straw). Glucose (at 2·5 g/100 g soil, and at 10 g/100 g straw) shortened survival.

When straws colonized in the presence of 0·5 g nitrogen/100 g straw were buried in soil supplied with 14·1 mg nitrogen/100 g soil, the level of soluble soil nitrogen reached equilibrium at 2–4mg/100g soil; this allowed rapid straw decomposition and, although the added soil nitrogen prolonged survival in straws that remained undecomposed, it also accelerated substrate exhaustion. Addition of 100 mg nitrogen/100 g soil was supra‐optimal for survival: although some nitrogen was necessary for maximum survival, the equilibrium concentration of soluble nitrogen (24–56 mg/100 g soil) was high enough in this case to have an inhibitory effect in addition.
Field biology and control of Phytophthora parasitica on papaya (Carica papaya) in Hawaii
Authors: HUNTER J. E. , BUDDENHAGEN I. W.
Published: February 2008

Epidemic attacks of Phytophthora parasitica on papaya fruits developed during wet, windy weather, but declined rapidly when the weather became dry. During rain, abundant sporangia were liberated from the mycelial mats on infected fruits, but none was trapped in dry air.

Collar rots and tree collapse caused by root rot occur irrespective of spray treatments and previous aerial infections on the same tree: they are no more prevalent in blocks with abundant aerial infections than in blocks with none. Basal rots occurred earlier and more frequently on plantings near abandoned diseased fields: they were scattered randomly and appeared before aerial infections.

It is suggested that new outbreaks might be initiated from seeds of infected fruit, in which chlamydospores have been found, or from infected nursery seedlings. Drosophila spp. were found to be occasional vectors of sporangia.

Control of aerial infections was obtained with maneb, basic copper sulphate, captan or difolatan. Spraying only the upper half of the acropetally developing fruit cluster gave much better control than spraying only the lower fruits.
The possible role of pathogenic fungi in local degeneration of Salvinia auriculata Aublet on Lake Kariba
Authors: LOVELESS A. R.
Published: February 2008

A patchy degeneration of weed mats of Salvinia auriculata in the sheltered mouths of rivers draining into Lake Kariba was reported in 1962 to be associated with a fungal attack. Laboratory isolations from degenerating plants yielded a saprophytic Alternaria sp. and a parasitic Spicariopsis sp. Degenerating plants failed to transmit the disease when placed among healthy plants, and the results of inoculation experiments with spores of Spicariopsis sp. were inconsistent with this fungus being a primary pathogen.

The characteristic feature of degeneration in the field was a mosaic of alternating ‘islands’ of diseased and healthy plants. Although the diseased plants showed the symptoms associated with Alternaria sp. and Spicariopsis sp., their characteristic distribution provided circumstantial evidence that degeneration was physiological in origin. This view was strengthened by the fact that sudd plants growing on degenerating areas of the Salvinia‘carpet’ were usually chlorotic. The presence of symptoms caused by the parasitic Spicariopsis sp. on degenerating plants could be explained by postulating that, after the plants have begun to degenerate, they are predisposed to infection by this fungus.

The association of degeneration with a particular type of riverine site suggests that a seasonal investigation of the hydrobiological conditions accompanying the development of weed mats at such sites would indicate the type of factor responsible for the disease. The original hope for a biological control of Salvinia auriculata by means of a parasitic fungus remains a theoretical possibility.
Splash dispersal of fungus spores and fungicides in the laboratory and greenhouse
Authors: HISLOP E. C.
Published: February 2008

A laboratory technique is described for the production of drops of simulated rain in which fungal spores were suspended. When such drops containing conidia of Botrytis fabae impacted on a target leaf the secondary droplets produced infections on receptor broad bean leaves. The capacity of fungicides applied to the target leaf to redistribute in secondary splash droplets was examined in terms of the infectivity of the spores in the droplets. The extent to which a copper fungicide reduced infection on the receptor leaves was related to the level and tenacity of the fungicide deposit on the target leaf. The effect of wetting agents on the redistribution of this fungicide could probably be explained by their influence on the tenacity of the initial deposit. In general the capacity of different fungicides to inhibit infection by the secondary droplets was related to the inherent toxicity of the fungicides to B. fabae. Implications of the dispersal of spores and fungicides by rain splash are briefly considered with reference to field conditions.
A laboratory method for assessing the toxicity of stomach poisons to slugs
Authors: HENDERSON I. F.
Published: February 2008

A method is described that allows the toxicity of stomach poisons to the grey field slug, Agriolimax reticulatus (Muller), to be measured in the laboratory. The relative toxicities of three commonly used molluscicides, as expressed by the median lethal dose values, were: sodium pentachlorophenate most toxic with a median value of 22·9 ± 2·5 μg/slug, metaldehyde next with one of 85·2 ± 4·0 μg/slug, and copper sulphate least toxic with one of 129·2 ± 5·9 to 131·6 ± 5·6 μg/slug. The technique allows a given dose of any poison, however repellent, to be administered, but does not measure the repellency or attractiveness.
Population fluctuations of Heterodera rostochiensis Woll. when susceptible potato varieties are grown continuously
Authors: JONES F. G. W. , PARROTT D. M.
Published: February 2008

When seven potato varieties susceptible to Heterodera rostochiensis were grown every year on the same small plots for 6 years with precautions to minimize soil movements, yields were inversely proportional to the number of larvae in the soil before cropping in the first year only. With all the varieties, numbers of larvae after harvest fluctuated around mean values and the fluctuations became smaller in successive years. Although conditions from year to year were as uniform as possible, there were differences in weather, incidence of potato blight (Phytophthora infestans), seed size and quality, and in planting dates. Analysis of soil temperatures and of heat accumulation did not suggest that conditions after planting caused the fluctuations. The smaller fluctuations with repeated cropping probably reflect the influence of population density on the size of the root system and are what would be expected from the curve relating pre‐ to post‐cropping numbers, which reaches a maximum before the reproductive rate decreases to unity.

A resistant potato hybrid ex andigena, also grown every year, usually outyielded the susceptible varieties and, by the sixth year, yielded at least twice as much as the mean of the six susceptible varieties.
Some effects of suction on the hatching eggs of Meloidogyne javanica
Authors: BAXTER R. I. , BLAKE C. D.
Published: February 2008

Development and hatch of eggs of Meloidogyne javanica was independent of suction between pF o and 3·6 but decreased rapidly between pF 3·6 and 4·2. Water was lost from the extracellular fluid of eggs containing developing embryos when the suction was above pF 3·6, causing a decrease in the mean volume of the eggs. The vitelline membrane of an egg is probably semipermeable and the osmotic pressure of the contents about 4 atmospheres (pF 3·6). The volume of the cellular contents of an egg did not increase during development and so the hydraulic conductivity of the soil is probably unimportant in hatching.

The results suggest that eggs of M. javanica hatch over a wide range of soil moistures. The inhibition of hatch at high suctions, involving the reversible removal of water, is a likely survival mechanism.
Evidence that toxins are not the causal factors of the specific apple replant disease*
Authors: SAVORY B. M.
Published: February 2008

Experiments were made to test the hypothesis that a toxin produced by or from apple roots is the causal factor of specific apple replant disease. In sand and vermiculite culture, apple leachates were not harmful to the growth of apples. In the field, apples exerted no effects on neighbouring apples other than competition effects. In pot and field experiments, the addition of apple root residues to fresh (unused) or fumigated soil depressed the growth of both apple and cherry test plants; similar additions to used (‘replant’) apple soil, however, improved the growth of apple, but not of cherry, test plants. It is concluded that specific apple replant disease is not caused by a toxin derived from root residues. It is suggested that the cause may rather be a rhizosphere microorganism.
The significance of temperature during sporulation on the biology of pycnidiospores of Mycosphaerella ligiilicola
Authors: BLAKEMAN J. P. , FRASER A. K.
Published: February 2008

The germination, infectivity and survival of pycnidiospores obtained from cultures of Mycosphaerella ligulicola grown at 15 and 26 °C were compared. Spores formed at 26° (‘26° spores’) were less able to germinate at low relative humidities and showed a narrower temperature range for maximum germination after 6 h. At high spore densities 26° spores showed self‐inhibition of germination and, over a range of lower densities, growth of their germ tubes was checked, which resulted in lower infection of leaf discs compared with 15° spores in which this phenomenon did not occur.

The fungus could be recovered from un‐sterile compost over a longer period after inoculation with 15° spores. Only after storage at a temperature well below zero was there a difference in viability between 15° and 26° spores.

It is thought that the potential advantage of producing larger numbers of spores at 26° would be realized only under optimum conditions for dispersal and infection. The smaller number of spores produced at 15° are likely to be successful under natural conditions.
Biochemical studies on plant tissues infected by Phytophthora palmivora (Butl.) Butl.
Authors: AKINREFON O. A.
Published: February 2008

Lesion formation in tomato and eggplant fruits infected by Phytophthora palmivora could be classified into three phases associated with changes in hydrolytic enzymes in the tissues. Phenolase, arabinofuranosidase and endo‐polygalacturonase activities were all higher than in healthy tissue. The enzymic effects seemed to be reflected in a fairly high loss of pectic materials in the infected tissue, especially the water‐insoiuble components. There was a significant negative correlation (r = ‐0·56) between pH of tomato and the endo‐polygalacturonase secretion in the infected tissues.

Paper chromatographic analysis of host metabolites showed little or no qualitative differences between the sugar contents of healthy and of infected tomato tissues; there were also no qualitative differences in the amino acid and the phenolic contents. Chlorogenic acid was detected in healthy but not in infected eggplant tissues and lesion maturation was associated with its disappearance. Gradual browning of the lesion was probably also associated with changes in cell membrane permeability of infected tissue.
Factors affecting aphid infestation of chrysanthemums
Authors: Wyatt I. J.
Published: February 2008

Large differences exist between chrysanthemum cultivars in their susceptibility to attack by Myzus persicae (Sulz.). This is due to a repellent factor which increases in the leaves as they age, but which varies from one cultivar to another. Aphid population growth is retarded, or even prevented, on resistant cultivars. If susceptible and resistant plants are in contact, the rate of population increase will be the same on both, but numbers will remain proportionately lower on the resistant cultivars. For instance, aphid numbers are normally forty times as high on B.G.A. Tuneful as on Portrait.

Aphids appear to select the cultivar or region of plant most suitable for reproduction (usually apical and basal leaves) but, as the plants and population grow, the aphids continually redistribute themselves. Within the limits of normal growing practice, cultural and environmental conditions have little effect on the aphids.

Brachycaudus helichrysi (Kaltenbach) and Aphis fabae Scop, have similar varietal preferences but, unlike Myzus persicae, they avoid senescent leaves and only colonize the apex.
An oscillating insect barrier
Authors: ARNOLD A. J.
Published: February 2008

A wide range of insects can be confined on the horizontal surface of areas surrounded by oscillating rings or chambers. The ability to retain insects on a selected surface may be useful in the bioassay of insecticides using residual film and other techniques, by diminishing the amount of anaesthesia required and any unwanted fumigant effects.
Susceptibility of the leatherjackets Tipula oleracea and T. paludosa to soil flooding
Authors: MEATS A.
Published: February 2008

A relation was found between temperature and the survival of larvae of Tipula oleracea and T. paludosa when submerged in tap water alone or on turf growing on a sandy loam flooded with still or disturbed water (experiments with soil always starting with freshly flooded soil). Larvae under water alone usually survived until they starved, whereas larvae submerged on soil died in a relatively short time. The periods of survival at a depth of 25 mm were the same for both large and small larvae of either species at any one temperature. The regression of log.‐log. survival time on temperature was a straight line, mean arithmetic values ranging from about 5 h at 20 °C to 122 h at 0 °C. Survival times at 25 mm were not increased by disturbing the water and the times at greater depths were no different, providing the water was still. If the water was regularly disturbed then the greater the depth the longer the survival time at any one temperature.

Survival times in deoxygenated water indicated that lethal conditions may not be entirely due to deoxygenation of the water.
Cocoa canker caused by Phytophthora palmivora
Authors: FIRMAN I. D. , VERNON A. J.
Published: February 2008

Canker disease of Theobroma cacao L. caused by Phytophthora palmivora (Butler) Butler gives rise to serious damage in Fiji and is common in the S.W. Pacific area. Fusarium decemcellulareBiick (imperfect stage of Calonectria rigidiuscula (Berk. & Br.) Sacc.) was constantly associated with P. palmivora in disorders of cocoa but was not found to be a primary pathogen. Most Amelonado cocoa trees were resistant to canker but there were differences in the reactions of other Forastero and of Trinitario types. The F1 generation of a local Trinitario selection, itself resistant, showed segregation resulting in a proportion of very susceptible plants. Isolates of P. palmivora from black pod, canker and green twigs were equally pathogenic, both to pods and seedling stems. Sporangial dimensions, particularly the length/breadth ratio, differed from those reported elsewhere. It is uncertain whether the reason that cocoa canker is more serious in some countries than others is because of differences in the pathogenicity of P. palmivora strains to bark or the genetic differences of the cocoa grown.