bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaf‐area development in King Edward potato plants inoculated with Verticillium albo‐atrum and V. dahliae
Authors: HARRISON J. A. C. , ISAAC IVOR 
Published: February 2008

SUMMARYLeaf‐area development in King Edward potato plants infected with Verticillium albo‐atrum and V. dahliae was examined both in plants with a normal growth pattern and in those where maturity had been artificially delayed. Methods are described for producing uniform, single‐stemmed, initially disease‐free host plants, and for measuring their total and green leaf areas throughout their development.Under both growth conditions the pathogens had no apparent effect upon the initiation of new leaves on the main axis of the plant, but they did influence their subsequent development. During the growing period the pathogens caused stunting, thus preventing the production of the potential maximum leaf area, while at maturity the chlorosis and necrosis of the diseased leaves and their premature fall reduced functional leaf area.In diseased plants in which maturity had been delayed, stunting at the apices was more apparent: internode length, leaf petiolar axis length and leaf area were all smaller than in healthy plants, the greatest reductions being shown in leaf area. Cells in the stunted leaves were fewer and smaller than those in healthy leaves.A direct result of leaf‐area reduction was the development of smaller tubers, with consequent reduction in the fresh weight, and some reduction in tuber number. V. albo‐atrum invariably proved to be more virulently pathogenic than V. dahliae; the use of an average Verticillium index was shown to be a reliable method for estimating relative virulence since it reflected both leaf area and yield reductions.Delaying host maturity and thus lengthening the period of extension growth conferred some resistance on plants infected with V. dahliae; symptom progression was stopped after its initial expression, and consequently leaf area was increased. This form of resistance was not shown in the plants inoculated with V. albo‐atrum.
The symptoms and causal agents of early‐dying disease (Verticillium wilt) of potatoes
Authors: ISAAC IVOR , HARRISON J. A. C. 
Published: February 2008

SUMMARYThe 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

SUMMARYSeveral 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

SUMMARYThe 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

SUMMARYOviposition 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

SUMMARYSyrphids 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

SUMMARYThe 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

SUMMARYA 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

SUMMARYStandard 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

SUMMARY2‐(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

SUMMARYTwo 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

SUMMARYSingle 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

SUMMARYTeleutospores 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

SUMMARYThe 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

SUMMARYLaboratory 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

SUMMARYThe 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

SUMMARYThirty 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

SUMMARYCocksfoot 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.