bluuebunny/crossref_metadata_2025 huggingface dataset:
The incidence of stalk rot (Fusarium spp.) on maize hybrids and its effect on yield of maize in Britain
Authors: COOK R. J.
Published: February 2008

Stalk rot was present in each of 78 maize crops and six hybrid maize trials examined between 1971 and 1975. Fusarium culmorum was the main cause of the disease and was isolated from 67 of the 82 samples from which isolates were made. Lodging was found to be related to, and a natural succession of, the earlier wilting symptom caused by infection with F. culmorum. Yield losses were estimated in 39 crops between 1973 and 1975 and the disease caused a mean reduction of 18‐7% in cob weight and 11‐2% in 1000‐grain weight of infected plants over the 3 yr of the survey.
Preservation of baled hay with propionic and formic acids and a proprietary additive
Authors: LACEY J. , LORD K. A. , KING H. G. C. , MANLOVE ROSEMARY
Published: February 2008

Field‐baled hay was incompletely preserved using propionic or formic acids. Results were most satisfactory, although moulding by Aspergillus glaucus group was still frequent, when die hay contained less than 30% water and propionic acid was used. However, much more propionic acid was needed than in laboratory experiments probably because poor distribution of acid in the bale, resulted in under‐treated pockets of hay where moulds tolerant to propionic acid could grow and then spread to areas that would otherwise have been adequately treated.

In Dewar flasks, moulds, particularly Paecilomyces varioti and the A. glaucus group, could spread from untreated hay into hay containing 2% w/w of propionic acid. Addition of 4 or 10% of propionic acid protected adjacent untreated hay from moulding. The concentration of propionic acid necessary to prevent flasks from heating and moulding increased with thickness of the untreated layers and with water content. Redistribution of acid in the bale after treatment was slow and much variation in acid levels occurred even between adjacent 1 cm segments of grass following storage. Spontaneous heating of moulding hay could cause migration of propionic acid in hay, assisting the spread of fungi. A proprietary additive did not prevent moulding at any hay water content tested.
Oxamyl sprays for the control of potato spraing disease caused by nematode‐transmitted tobacco rattle virus
Authors: ALPHEY T. J. W.
Published: February 2008

Field trials on sites infested with trichodorid nematodes in Scotland tested the effects of dichloropropene‐dichloropropane mixture (D‐D), thiofanox, and granules and foliar sprays of oxamyl on the incidence of spraing disease in potato (cv. Pentland Dell) tubers. D‐D was effective in controlling spraing on all three sites, thiofanox was ineffective on the one site tested. On two sites oxamyl granules and sprays, alone and together, significantly decreased the amount of spraing. Those treatments including a spray were more effective than granules alone. At the third site different rates and times of application of sprays were tested.
Principles of insecticide action on mushroom cropping: incorporation into casing
Authors: WYATT I. J.
Published: February 2008

The incorporation of organophosphorous insecticides into the casing layer of mushroom beds reduces the numbers of mushrooms, according to a logistic relationship with log10 (dose). The cumulative numbers at any flush are affected in this way, and the response of individual flushes may, therefore, be represented by the difference between two logistic curves. This explains the observed increases in numbers in the second and third flushes following diazinon treatment and in the fourth following thionazin, pirimiphos‐methyl and pirimiphos‐ethyl. No compensation in numbers followed chlorfenvinphos treatment. This decreasing response pattern reflected the increasing residual action of the insecticides.

Mushroom size was inversely related to numbers but even when numbers in any flush were unaffected by the treatment, there was usually an increase in size. Thus yield increases occurred in most flushes at commercial concentrations of four insecticides (thionazin compensated only in the fourth flush) and total yields were increased by 8 to 13%.
The effect of inoculation with an attenuated mutant strain of tobacco mosaic virus on the growth and yield of early glasshouse tomato crops
Authors: CHANNON A. G. , CHEFFINS N. J. , HITCHON G. M. , BARKER J.
Published: February 2008

In trials in 1973‐5 at the Glasshouse Investigational Unit for Scotland, the yield of fruit from tomato cv. Eurocross BB inoculated at the seedling stage with the Mil‐16 attenuated strain of tobacco mosaic virus was 5–8‐9‐4% greater than that from uninoculated plants which became naturally infected with a severe indigenous strain of the virus within 7–8 wk of planting. The increase in fruit yield, particularly of better grades, resulted in higher gross financial returns (up to 25p/plant) from inoculated plants. The yields from the Mil‐16 protected plants were up to 14% greater than those from plants artificially inoculated at the seedling stage with the indigenous severe virus.

Inoculation with Mil‐16 had little adverse effect on early growth or the rate of fruit development on the first five trusses, but in 1973 the final yield of inoculated plants was depressed c. 5% compared with that from plants substantially free from infection for 14 wk after planting.

In 1 year's test no benefit from inoculation with Mil‐16 was recorded in cv. Cudlow Cross.
Incidence, field spread, seed transmission and effects of broad bean stain virus and Echtes Ackerbohnenmosaik‐Virus in Vicia faba in eastern Scotland
Authors: JONES A. T.
Published: February 2008

In eastern Scotland seed‐borne infection with broad bean stain virus (BBSV) and/or Echtes Ackerbohnenmosaik‐Virus (EAMV) was detected in five of 39 seed lots of field bean in 1975 and in four of 21 commercial crops of field bean or broad bean sampled in 1975 or 1976. Tests failed to detect the main weevil vector of these viruses, Apion vorax, in 1975 and 1976 but Sitona weevils were found in most crops and were numerous in many, reaching maximum numbers in August. No spread of BBSV and EAMV was detected in commercial crops containing seed‐borne infection. In experimental field bean crops containing plants manually inoculated with virus, no virus spread was detected in 1975, and only 0–015% uninoculated plants became infected with EAMV in 1976. Sitona, therefore, was an inefficient vector.

The percentage of virus infection in seed harvested from field bean plants manually inoculated 3, 5, 7 and 11 wk after emergence in the field was 1–5, 2–7, 0–4 and 0–06 for BBSV and 0–5, 2‐1, 0–6 and 0 for EAMV respectively. Seed harvested from unrogued and rogued plots of field bean grown from seed containing 3–4% seed‐borne infection produced 0–05% and no infected plants, respectively. Yield losses in field bean plants manually inoculated with virus before flowering were up to 20% but were much greater in plants infected through the seed. Loss in yield was largely caused by a decrease in number of seeds per pod.

The absence of A. vorax, the late arrival of Sitona weevils in the crop and their inefficiency as vectors, and the smaller effects of BBSV and EAMV on crop yield than in southern England appear to make eastern Scotland very suitable for the production of bean seed free from BBSV and EAMV.
Effects of host resistance on the development of haustoria and colonies of oat mildew
Authors: CARVER T. L. W. , CARR A. J. H.
Published: February 2008

Colony development of Erysiphe graminis f.sp. avenae race 2 was studied on detached leaf segments of a range of Avena hosts with different levels of resistance, none of which possesses known specific gene resistance to this race. Resistance affected the length attained by mature primary haustoria, and also colony size as assessed by numbers of haustoria and conidiophores produced per colony 5 days after inoculation. A more accurate assessment of the size of mature haustoria was provided by the total length of their digitate processes. At the primary haustorium stage resistance affected not only haustorial size, but also haustorial efficiency measured as colony growth per unit size. Adult plant resistance of some hosts decreased haustorial size and/or efficiency in colonies on the fifth in comparison with the first formed leaf.
A technique for measuring the susceptibility of wheat bulb fly larvae to insecticides in the laboratory
Authors: SMITH CLARA , GRIFFITHS D. C.
Published: February 2008

A simple assay is described for measuring the toxicity of insecticides to larvae of wheat bulb fly (Delia coarctata) in the laboratory. The method should be suitable for other small soil insect larvae that cannot be obtained in large numbers and are difficult to treat and confine. A limitation of the technique is that it works only with insecticides that are soluble enough to be toxic in aqueous solution.
Comparison of fungicides for the control of Rhizoctonia solani causing datnping‐off of mung bean (Phaseohis aureus)
Authors: KATARIA H. R. , GROVER R. K.
Published: February 2008

Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar‐bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2‐n‐octyl‐4‐isothiazole‐3‐one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC50 values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3‐hydroxy‐5‐methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC50 of 214 μg a.i./ml.

Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate‐methyl, dichlozoline and Ohric gave 80–90% control of damping‐off of mung bean seedlings. A single soil drench with thiophanate‐methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate‐methyl was used as a post‐inoculation soil drench than when benomyl or chloroneb were used.
Nematodes in Scottish forest nurseries
Authors: BOAG B.
Published: February 2008

Seven hundred soil samples from 41 forest nurseries were collected between 1972 and 1975 and examined for plant parasitic and predatory nematodes. Rotylenchus goodeyi, Trichodorus primitivus, Cephalenchus emarginatus and Tylenchus davainei occurred in most nurseries but their numbers were generally lower than those of R. robustus and Paratrichodorus pachydermus. In a glasshouse experiment as few as 10 R. robustus decreased the growth of Sitka spruce seedlings. It was estimated that Rotylenchus and trichodorid nematodes probably retarded the growth of some seedling trees in eight of the nurseries sampled. During the survey, Trichodorus sparsus was found for the first time in Great Britain and Paralongidorus maximus for only the third time. Since both these species were found in nurseries they were probably introduced and are ideally situated to be more widely disseminated.
Effect of gibberellic acid on senescence of isolated petals of carnation
Authors: GARROD J. F. , HARRIS G. P.
Published: February 2008

Application of gibberellic acid (GA3) to isolated petals of carnation growing in agar or a liquid medium resulted in a delay in senescence by up to 4 days. Sucrose and 8‐hydroxy‐quinoline sulphate were also effective in delaying senescence but combined effects with GA3 were not additive.
A method for the extraction and enumeration of resting spores of Plasmodiophora brassicae from infested soil
Authors: BUCZACKI S. T. , OCKENDON JEAN G.
Published: February 2008

A technique is described for the extraction of the resting spores of Plasmodiophora brassicae from soil. After deflocculation, coarse mineral matter was filtered from soil samples and the remainder mixed with 40% sucrose. The mixture was allowed to stand for 2–5 days; this enabled most mineral particles to settle out leaving the spores in suspension. The spores were counted optically on a microscope using Nomarski interference contrast optics, although preliminary studies had indicated that electronic image analysis was a more satisfactory method. Good recovery of spores was achieved from artificially infested soils containing 106 spores/g but the technique can be satisfactorily applied to less heavily infested soils. Clubroot symptoms developed on seedlings dipped in suspensions of spores recovered in this way.
Effects of chemical treatments for mildew control at different times on the growth and yield of spring barley
Authors: JENKYN J. F.
Published: February 2008

Experiments in 1973 and 1974 tested the effects of ethirimol seed treatment and the timing of single sprays of ethirimol or tridemorph, on mildew control and the growth and yield of spring barley. These treatments were compared with selected combinations of two treatments designed to give longer protection. In 1973, combinations of seed treatment and spray, or two sprays, did not yield better than the best component treatment applied alone or the most effective single spray of tridemorph applied on 1 June. In 1974, mildew developed usually early and yields were increased by applying ethirimol to the seed plus a tridemorph spray or two tridemorph sprays. However, barley sprayed once with tridemorph on 20 May, the expected best date, yielded more than barley receiving a seed treatment of ethirimol plus a tridemorph spray applied on either 3 or 12 June. Sprays of captafol and tridemorph, applied as separate treatments, successively to the same plots on three occasions, gave the best yields in both years. Treatments most affected ear number but they did have some effect on all components of yield. In 1974 there was a significant relationship between ear number and the variance of the number of grains per ear.
Field experiments on sugar‐beet powdery mildew, Erysiphe betae
Authors: BYFORD W. J.
Published: February 2008

Sugar‐beet powdery mildew, Erysiphe betae appeared in East Anglia in late July 1976 and became wide‐spread in eastern England during August and September but was scarce in crops in the north and west of England. Fentinhydroxide, sulphur, benomyl and ethirimol controlled the disease but benomyl applied once only and ethirimol were less effective than the other materials. In heavily infected crops two sulphur sprays, the first applied at the onset of the mildew attack, increased sugar yield by 13%. A single early sulphur spray increased yield on average by 9% giving a return of six to seven times the cost of treatment. When the first spray was delayed, mildew control was less effective.
Effect of machine‐harvester wounds and Leptosphaeria coniothyrium on yield of red raspberry
Authors: HARGREAVES A. J. , WILLIAMSON B.
Published: February 2008

When wounds on raspberry canes caused by machine harvesting in the previous year were infected by Leptosphaeria coniothyrium the potential yield per cane was reduced by 45% compared with that of uninfected hand harvested canes. However, the corresponding reduction per plot was less (c. 25%) because the yield of wounded but uninfected canes was not reduced and some canes were not wounded. The advantages and disadvantages of recording potential yield per cane are discussed.
Capsulation and virulence in Erwinia amylovora
Authors: BENNETT R. A. , BILLING EVE
Published: February 2008

Evidence is presented that capsulation may be one virulence determinant for Erwinia amylovora, the fireblight pathogen.

When 15 virulent and seven avirulent strains were grown on a medium containing asparagine as the only source of carbon and nitrogen, or yeast peptone agar, or on a sugar medium containing an inorganic source of nitrogen, capsule production and virulence were not correlated. However, if a sugar or sugar alcohol was added to the asparagine medium or to yeast peptone agar all the virulent strains produced some or many capsulated cells whereas six of the avirulent ones did not. Capsules were also produced by all the virulent strains during infection. The existence of a seventh avirulent strain which was capsulated on all media except unsupplemented asparagine agar, suggested that capsule production was not the only virulence determinant.
Translocation of 14C‐dieldrin from small droplets on cotton leaves
Authors: PHILLIPS F. T. , ETHERIDGE P. , KAVADIA V. S. , SETHI G. R. , SPARROW P. E.
Published: February 2008

Dieldrin (HEOD) spread from dried residues formed from droplets of emulsions and crystalline suspensions applied to the upper surfaces of cotton leaves (Gossypium species).

The amounts of radiolabelled insecticide reaching defined areas of leaf‐surface bearing adhesive tape (Sellotape) were measured quantitatively by scintillation counting. Autoradiography supported these results in demonstrating the extent of insecticide movement in the leaf.

Up to one‐fifth of the applied dose spread more than 8 mm across the leaf surface within a day (lateral movement).

Penetration to the lower surface (vertical movement) took place within 4 days, depending on the leaf thickness, which itself was greatly affected by the growing conditions. During this process some dieldrin formed a derivative, possibly a hydroxydieldrin, and some was sorbed at the sites of the lysigenous secretory glands within the leaf.

Dieldrin spreads from a deposit (representing that left by a spray droplet) on cotton leaf in all directions to a greater extent and more rapidly than previously supposed.
Physiological studies of a hybrid between populations of Dactylis glomerata from contrasting climatic regions. I. Inter population differences
Authors: EAGLES C.F. , OTHMAN OMAR B.
Published: February 2008

A study of the physiological responses of a hybrid between a North European population and a colchicine‐induced autotetraploid of a Portuguese population of Dactylis glomerata subspecies lusitanica showed an intermediate response of the hybrid for many characters. However, the hybrid resembled one or other of the parents in the more favourable expression of certain characters in controlled environments at 20°C, 16 h photoperiod and 8 °C, 8 h photoperiod. Rate of dry‐matter production of the hybrid did not differ significantly from that of the northern parent at 20 °C, 16 h and that of the Portuguese parent at 8 °C, 8 h. Leaf growth of the hybrid at 8 °C, 8 h was greater than that of the northern parent and together with the high percentage survival in a freezing test may indicate a role for similar hybrids in the development of potential varieties with improved seasonal distribution of dry‐matter production.
Interactions in fireblight infections
Authors: Billing Eve , Bennett R. A. , Hutson R.
Published: February 2008

In the host, Erwinia arnylovora (Burrill) Winslow et al. travels primarily in the inter‐cellular spaces of immature cortical tissue; progress in mature tissue is restricted. Only in the later stages of infection are saprophytic bacteria such as Erwinia herbicola (Löhnis) Dye commonly found in association with the pathogen. Their effect on the persistence of the pathogen is still uncertain though commonly assumed (with little supporting evidence) to be inhibitory.

Most interaction studies have concentrated on the early stages of infection. The interactants have been inoculated prior to or together with E. amylovora and they have included avirulent E. amylovora, phyto‐pathogenic pseudomonads, E. herbicola and other saprophytes or cell components including DNA. Our experience reflects that of other workers in that interactants only inhibit at high doses or at high numbers relative to the pathogen. Prior inoculation is not always necessary for protection.

In our preliminary studies of the fate of interactants, the outcome varied. Where infection progressed the interactant disappeared, persisted only at the point of inoculation or progressed alongside the pathogen. Where there was protection, both pathogen and interactant disappeared from the tissues or only the interactant persisted at the site of inoculation. Crown gall apart (possibly a special case), observations with other bacterial plant diseases have been similar to those with fireblight with an added one of stimulation of infection by the interactant.

The underlying mechanisms of protection probably vary with different interacting systems and cannot always be attributed to a hypersensitivity reaction or to bacteriophage or bacteriocin activity. If a host response is involved, it seems pertinent to ask whether there are simpler ways of achieving protection of growing tissue other than by using bacteria and their products. With epiphytic bacteria two major problems are the achievement and maintenance of high enough populations at critical sites and the lack of major transmitted or translocated effects beyond the site of interaction.
Biological control of crown gall, Agrobacterium tumefaciens
Authors: Garrett Constance M. E.
Published: February 2008

Biological control of crown gall caused by Agrobacteriurn turnefaciens (Smith & Townsend) Conn, pioneered by Dr A. Kerr in South Australia, is effected through the establishment of a high population of the related non‐pathogen A. radiobacter (Beijerinck & van Delden) Conn, strain 84 in the rhizosphere of susceptible plants. Strain 84 produces a bacteriocin to which many strains of the pathogen in Australasia, North America and Britain are sensitive.

The disease is present in Britain on a variety of hosts including cherry. At East Malling cherry leaf scars, invaluable as an avenue of infection for bacterial canker infectivity titrations, have been used successfully in crown gall studies. Live cells of strain 84, but neither an avirulent strain of the pathogen nor a soil bacterium highly antagonistic to A. tumefaciens in vitro, inhibited gall formation in cherry leaf scars. Heat‐killed cells had no effect.

In a field experiment at East Malling hardwood cuttings of the new rootstock Colt have been dipped in strain 84 and total inhibition of crown gall is expected to ensue. The results of other experiments where the disease is already established on cherry‐rootstock layer‐beds and in blackberry plantations are less predictable. In time we hope to solve this problem. Only time will show whether this method of biological control is long lasting or will eventually break down.
Lignification in wheat roots parasitised by Gaeuntannomyces graminis and Phialophora radicicola
Authors: Cowan M. C.
Published: February 2008

Preliminary results suggest a possible relationship between lignin synthesis in wheat roots and the observed interaction between Gaeumannomyces graminis (Sacc.) Arx & Olivier and Phialophora radicicola Cain var. graminicola Deacon when they parasitise wheat roots. It was found that colonisation of wheat roots by P. radicicola resulted in a qualitative change in the lignin of the root, such that the content of the p‐hydroxy type of aromatic nucleus was reduced almost to zero. It was also found that some of the metabolic precursors of lignin were inhibitory to the growth of G. graminis in Petri‐dish culture. Most inhibitory of these precursors was caffeic acid, which reduced the growth rate of G. graminis by half at a concentration of 37 ppm. It is tentatively suggested that colonisation by P. radicicola results in an increased activity of polyphenol oxidase in the root tissues. This would lead to a more rapid synthesis of caffeic acid, with a depletion of the level of p‐coumaric acid, and probably an increase in the levels of ferulic acid and sinapic acid. As well as bringing about a change in the composition of the lignin of the root, as the results show, the possible accumulation of caffeic acid in the root tissues might explain the greater resistance to infection by G. graminis observed in roots colonised first by P. radicicola.
Interactions between seed‐borne wheat pathogens
Authors: Odebunmi‐Osikanlu Y. K.
Published: February 2008

Fusarium nivale Auct., Fusarium culmorum (W.G.Sm.) Sacc. and Septoria nodorum Berk. were used to inoculate wheat seed either singly or in mixtures. Data collected from glasshouse and field experiments suggest that less pre‐emergence death of seedlings and fewer seedlings with lesions occur when F. nivale and F. culmorum are present on the seed together than when F. culmorum only is present. There is also clear evidence that this reduction in disease cannot be attributed to the halving of the spore concentration of each species in the mixture used.
Interactions between Rhizoctonia tuliparum and soil microorganisms
Authors: Gladders P. , Coley‐smith J. R.
Published: February 2008

Rhizoctonia tuliparum Whetzel & Arthur is a winter active soil‐borne pathogen, which causes the grey bulb rot of tulips and Dutch irises. The fungus survives by means of sclerotia.

It was found that the sclerotia only germinated in unsterile soil at low temperatures (0–10 °C). Germination in sterile soil occurred over a wider range of temperatures (0–25 °C) but was inhibited at 20 °C after the addition of a suitable bacterial inoculum.

An unidentified pyrone antibiotic was leaked by sclerotia which had been air‐dried and re‐wetted. This could be detected in vitro using an agar medium seeded with a spore suspension of Bacillus subtilis Cohn emend Prazmowski. In soil, however, material leaked by sclerotia stimulated both bacteria and fungi.

Undried, air‐dried and oven‐dried (non antibiotic) sclerotia persisted equally well in soil over 2 yr. This suggests that the resistance to lysis of sclerotial cell walls may be important in the long term survival of this organism.
A rapid technique for analysing diets of invertebrate predators by electrophoresis
Authors: MURRAY R. A. , SOLOMON M.G.
Published: February 2008

A technique has been developed for the rapid determination of some species of prey consumed by mites and insects. The method detects prey enzymes within the gut of a predator by polyacrylamide gradient gel electrophoresis and subsequent staining for esterase activity. It is sufficiently sensitive to detect fruit tree red spider mite (Panonychus ulmi) esterases within the gut of a single predacious mite (Typhlodromus pyri) for at least 31 h after feeding. The method has been used to demonstrate feeding relationships among a range of insect and mite predator and prey species in the laboratory and in the field.
Predisposing effects of Eyespot (Pseudocercosporella herpotrichoides) on Septoria nodorum infection of winter wheat
Authors: JONES D. GARETH , JENKINS P. D.
Published: February 2008

Plants of two cultivars of winter wheat were inoculated with Pseudocercosporella herpotrichoides at Growth Stage 4 and with Septoria nodorum at Growth Stage 9 or 10.5. Significantly higher levels of S. nodorum developed on the leaves of eyespot infected plants but there was no significant interaction in terms of grain yield. Eyespot infection markedly predisposed the developing seed to infection by S, nodorum.

The significance of these results is discussed with reference to the epidemiology of S. nodorum and in relation to the strategy for fungicide control of cereal diseases.
Evaluation of fungicides for control of South American leaf blight of Hevea brasiliensis
Authors: CHEE K. H.
Published: February 2008

Of 43 fungicides tested in vitro, 19 showed strong, seven moderate and 17 weak inhibition of germination of conidia and ascospores of Microcyclus ulei. The formation of lesions on Hevea brasiliensis leaf discs was also suppressed by the first category of fungicides as well as by the five adjuvants tested. Ascospores were not released when perithecia were treated with urea, thiabendazole or alcoholic mercury chloride at 10.00, 0.10, 1.00 g/1 respectively; other fungicides had no such inhibitory effect.

In field trials, thiophanate methyl (0.07% a.i.) and benomyl (0.025% a.i.) were most effective in controlling leaf infection, followed by chlorothalonil (0.15% a.i.) and mancozeb (0.32% a.i.). Benomyl suppressed conidial sporulation, whereas one application of thiophanate methyl (0.14% a.i.) to perithecia inhibited ascospore release; half of this concentration applied to conidial lesions or pycnidia caused the perithecia formed subsequently to abort. Thiophanate methyl thus shows promise for SALB control and elimination and benomyl may be valuable as a supplement in later rounds of spraying to control conidial sporulation.

After 6 days of showery rain (2 mm for 17 min per day), water collected from sprayed leaves still gave complete inhibition of spore germination. However, inhibition was markedly reduced after 6 days of heavy rain (over 8 mm for 24 min per day).
Effects of some surfactant fungicides on Rhizobium trtfolii and its symbiotic relationship with white clover
Authors: FISHER D. J. , HAYES ANN L. , JONES CHRISTINE A.
Published: February 2008

Effects of the surfactant apple mildew eradicants Manoxol OT, Alk 3, Triton X45, PP 222, Ethylan CP, Hyamine 3500, Aromox DMMCDW and Aromox C12W on growth and respiration of R. trifolii in vitro and on its symbiotic nitrogen fixation in association with white clover were measured. Most treatments reduced growth up to 8 wk; after 12 wk plant weight and nitrogenase activity were significantly reduced (P = 0.01) by Triton X45, Manoxol OT and PP 222 at concentrations of 1000, 2500 and 5000 μg/gram of soil respectively.

Electron microscopy showed that bacteroids in root nodules where nitrogen fixation was inhibited had contracted away from the host membrane leaving an intracellular space. Damage to the bacteroid membrane was apparent. Surfactants had no demonstrable effect on adhesion of the bacteria to root hairs.

In apple orchards run‐off of surfactant fungicides, applied to apple trees at the recommended rates is unlikely to have adverse effects on Rhizobium nodulated white clover.
Distribution of carbon‐14 assimilated by wheat awns
Authors: OLUGBEMI L. B.
Published: February 2008

The pattern of distribution of carbon assimilated by awns was investigated in two lines of Triticum aestivum. Single awns on basal florets of spikelets in the central part of the ear were dosed with 14CO2. Five days after dosing, 99% of the carbon‐14 recovered was in the spikelet bearing the awn. Of the carbon‐14 exported from the treated awn 57% went to the grain of the first floret, 1% to the second, 28% to the third and 7% to the fourth.
Modelling canopy net photosynthesis by isolated blocks and rows of chrysanthemum plants
Authors: ACOCK B. , CHARLES‐EDWARDS D. A. , FITTER D. J. , HAND D. W. , WILSON J. WARREN
Published: February 2008

A model describing the response of canopy net photosynthesis by isolated blocks and rows of chrysanthemum plants to incident light flux density is reported. The model combines a description of the light environment within an isolated array of plants with a description of the response of leaf net photosynthesis to light flux density.

The leaf parameters in the model were estimated by analysis of data for the response of canopy net photosynthesis by a closed crop of chrysanthemum plants to incident light flux density at two carbon dioxide concentrations. These leaf parameter values were then used to simulate the response of canopy net photosynthesis to incident light flux density by an isolated block and double row of chrysanthemum plants. The simulated responses were found to be in close agreement with the measured responses.
Effects of irradiance and water supply on grain development in wheat
Authors: BROCKLEHURST P. A. , MOSS J. P. , WILLIAMS WATKIN
Published: February 2008

The effects of two levels of irradiance and of water supply on grain development in two cultivars of winter wheat were studied by imposing treatments during the phases of cell production and cell expansion in the endosperm. The storage capacity of the grain was determined by cell number in the endosperm, which was reduced by both treatments during the cell production phase. Changes in cell number caused by the treatments were due to changes in the rate of production of cells; the duration of the cell production phase was constant. Weight per grain at maturity was proportional, both within and between cultivars, to the number of endosperm cells, except when treatments altered the supply of assimilate to the grain during the cell expansion phase.

Reducing irradiance and water during the cell expansion phase decreased the rate of accumulation of dry matter in the grain and reduced weight per grain at maturity, with no effect on the duration of grain filling. Shrivelled grain resulted from a failure of the endosperm cells to fill completely, and was characterised by a reduction in the number of ‘B’‐type starch granules.
A wilt disease of coconuts from Trinidad associated with Phytomonas sp., a sieve tube‐restricted protozoan flagellate
Authors: WATERS HENRY
Published: February 2008

A wilt disease of coconut palms in Trinidad has been responsible for the death of more than 15 000 palms in the last 2 years. Symptoms of the disease include: loss of nuts, premature browning of successively younger leaves, necrosis of open and unopened inflorescences and of the young unexpanded leaves at the centre of the crown; rotting of the growing point, stem apex and roots.

Samples from each of 10 diseased palms contained flagellates which were classified as trypanosomatid protozoans of the genus Phytomonas. The protozoans, which by squeezing could be expressed easily from tissues for observation by phase contrast light microscopy, were 1–1.5 μm wide and 27 μm long including the flagellum which was approximately 7 μm long.

Sections of inflorescence rachillae from diseased palms revealed that the phytomonads were restricted to the sieve tubes. Phytomonas was always associated with diseased palms but it was never found in healthy palms.

A brief description of the ultrastructure of the presumed pathogen of wilt disease is also given.
The effect of carbendazim‐generating fungicides with and without a mineral oil additive on tomato stem lesions caused by carbendazim‐sensitive and tolerant strains of Botrytis cinerea
Authors: CHANNON A. G. , THOMSON MOIRA C.
Published: February 2008

Isolates of Botrytis cinerea were obtained from tomatoes in several localities in the West Scotland. Some isolates grew on agar containing 100 mg/1 benomyl (carbendazim‐tolerant), while others did not (carbendazim‐sensitive).

Pot‐grown tomato plants treated with benomyl and other carbendazim‐generating fungicides, applied either as sprays or soil drenches, were inoculated on the leaf scars with some of these isolates. On treated plants the carbendazim‐tolerant isolates formed lesions which were about as large as those on untreated plants. Sensitive isolates formed much smaller lesions on treated plants.

There was evidence that the increase in lesion size during the period 7–14 days after inoculation with a carbendazim‐sensitive isolate was less on plants sprayed with benomyl or carbendazim with added mineral oil (2% Actipron) than on plants to which the fungicides alone had been applied. No such effect was recorded with thio‐phanate‐methyl. There was also an indication that the addition of Actipron to a benomyl spray improved the effect of the fungicide against two tolerant isolates, though there was no effect on the relative increase in lesion size during the second week after inoculation.

In two tests the addition of 2% and 4% Actipron to benomyl soil drenches did not improve the level of leaf scar lesion control.
Distribution, host range, properties and purification of cassava latent virus, a geminivirus
Authors: BOCK K. R. , GUTHRIE E. J. , MEREDITH GINA
Published: February 2008

Cassava latent virus (CLV) is almost entirely confined in East Africa to upland cassava‐growing areas west of the Rift Valley, where it is often associated with cassava mosaic disease (it was isolated from 27 of 38 cassava plants with mosaic, but not from 24 without mosaic). However, it is not the causal agent, because it was not recovered from any of 31 mosaic‐diseased plants in coastal districts. All attempts to return CLV to cassava failed.

The host range of CLV appears to be limited to Euphorbiaceae (Manihot) and Solanaceae (Nicotiana, Datura, Nicandra, Solanum). N. clevelandii proved the most useful assay and propagation host. The dilution end‐point of CLV was about 10‐3, thermal inactivation point about 55°C, and longevity in vitro about 3 days.

CLV was purified by clarification of leaf extracts with butanol/chloroform mixtures. Purified preparations (A 260/A 280 ratio c. 16) contained numerous 30 20 nm paired particles with a sedimentation coefficient (s20w) of 76 S. Treatment with RNase and DNase showed that the viral nucleic acid is DNA; CLV closely resembles maize streak virus but is not related to it serologically. The cryptogram for CLV is D/1: 0.8/*: S/S: S/*, geminivirus group.
Host plan preferences of Oscinella spp. (Diptera: Chloropidae) in the laboratory
Authors: Vickerman G. P.
Published: February 2008

The oviposition preferences of Oscinella frit, O. vastator, O. nitidissima, O. albiseta andO. nigerrima for differenct Gramineae were investigated in the laboratory. O. frit, laid most eggs on oats, Lolium multiflorum and Festuca rubra, relatively few eggs were laid on barley and virtually none on Dactylis glomerata None of the other Osinella species oviposted on cereals. Of the other species, O. vastator appeared to be the most polyphagous and the preferred hosts were L. multiflorum, Lolium perenne and Festuca pratensis; few eggs were laid on either F. rubra, Agrostis tenuis or Poa pratensis. The host ranges of the remaining species were much more limited. Although a few eggs were laid by O. nitidissima on Lolium, the preferred host was A. tenuis. Oscinella albiseta oviposited only on D. glomerata whilst nearly all the eggs laid by O. nigerrima were deposited on shoots of Arrhenatherum elatius. The distribution of eggs by O. frit on L. multiflorum and A. tenuis was different from that on oats; on grasses most eggs were laid inside withered leaf sheaths whereas on oats most were deposited inside the coleoptile. The oviposition sites of O. nitidissima, O. nigerrima and O. albiseta on their respective host grasses were similar to those of O. frit on grasses. O. frit laid most eggs on grasses which were at the five‐leaf stage and tailoring.
Evalutiaon of four isomers of 3‐butyl‐5‐methloctahydroindoliz, a component of the trail pheromone of pharaoh's ant, Monomorium pharaonis
Authors: Edwards J. P. , Pinniger D. B.
Published: February 2008

Four isomers of 3‐butryl‐methyloctahydroindolizine (monomorine 1), a major component of the trail pheromone of Monomorium pharaonis, was tested for attractant and trail‐initiating activity, One isomer showed attractancy and, under colony condition, tow initiated trail‐following bahaviour. Only the all‐cis isomer (monomorine 1a) had both attractant and trail‐initiating activity. The results indicated that these compounds may have only limited potential for use in control measures against this species.
Host and environmental effects on the infection of maize by Puccinia sorghi. II. Post‐penetration development
Authors: Mahindapala Ranjith
Published: February 2008

The numbers of pustules which subsequently developed on maize seedlings incubated at 5, 10, 15, and 20 °C and 100% r.h. were directly related to the temperature and length of incubation.

The generation time was 16 days at 10 °C, 10 days at 15 °C, 7 days at 20 °C and 5 days at 25 °C. Increase in urediniospore production was observed with increase in temperature.

Increase in the inoculum concentration up to 5 × 104 urediniospores/ml increased the number of resultant uredinia. However, further increases did not increase uredinia‐formation.
Studies on plant growth‐regulating substances LIII. The conversion of certain substituted ethylamines to active growth substances in plants
Authors: Price R. , Albores M. , Wain R. L.
Published: February 2008

A number of substituted phenylethylamines have been synthesised and their plant growth‐regulating activities, in standard wheat and pea tests, have been determined and compared with those of related substituted phenoxyethylamines, phenylacetic acids and phenoxyacetic acids.

The effects of applying the most active amines to various plant species are described and the results are considered in relation to the possible ability of the plant to convert the amine into the physiological active acetic acid derivative.
Some factors affecting the build‐up of cereal aphid infestations in winter wheat
Authors: HENDERSON I. F. , PERRY J. N.
Published: February 2008

Aphid populations were measured at 14‐day intervals during May to July 1974 in 17 fields of wheat at 10 sites along an 85 km transect running east from Hertfordshire to the Essex coast. Metopolophium dirhodum was the most numerous species initially, but was later superseded by Sitobion avenae. Rhopalosiphum padi was third in order of abundance.

Several characteristics of each site and crop were examined in relation to the development of aphid infestations: two were associated with inter‐site differences in aphid infestation. Infestations started earlier at the eastern than at the western sites due to the earlier arrival of alate migrants, and this resulted in higher peak populations densities of R. padi but not of M. dirhodum or S. avenae. Greater aphid densities were associated with crops having low nitrate concentrations in plant sap in the early stages of growth.
Witches' broom disease of cocoa Crinipellis perniciosa) in Ecuador
Authors: Evans H.C.
Published: February 2008

Two pathotypes of Crinipellis perniciosa were found in both eastern and western Ecuador. The cocoa strain was highly pathogenic to species of the genera Theobrotna and Herrania and caused the witches' broom disease. The liana strain was weakly or non‐pathogenic to cocoa and its allies; it is endemic in the forests of Ecuador on lianes, shrubs and trees and is possibly parasitic in these tissues. The taxonomic position of the fungus is discussed.
Witches' broom disease of cocoa (Crinipettis perniciosa) in Ecuador.
Authors: CRONSHAW D. K. , EVANS H. C.
Published: February 2008

Inoculation of cocoa with basidiospores of the witches' broom fungus Crinipellis perniciosa showed that stem, petiole and pulvinus tissues of unhardened flushes and also exposed wound surfaces were susceptible to infection in addition to the growing tip. Inoculation of flower cushions and young pods showed that carrot‐shaped pods were usually the result of fertilisation of systemically infected flowers. In the absence of fertilisation such flowers produced parthenocarpic pods or chirimoyas. Transmis‐sion of the fungus via infected beans was demonstrated and this may be a potent method of long‐distance dispersal.
The effect of inoculation with Selenophoma donacis at different growth stages on spring barley cultivars
Authors: BROKENSHIRE T. , COOKE B. M.
Published: February 2008

Two spring barley field trials were established to study the importance of the time of Selenophoma donacis inoculum arrival on disease development and subsequent grain yield and quality. Inocula of two spore concentrations were applied to four barley cultivars at all combinations of three growth stages, tillering, stem extension and heading. The response varied with the stage of growth at inoculation; plants were susceptible at tillering, more resistant at stem extension and became highly susceptible at heading. Under wet conditions one application of spores at tillering gave rise to severe disease levels at heading. Treatments involving double and triple inoculum applications gave the highest disease levels on the upper leaves and awns resulting in significantly lower yields and grain quality. Significant relationships were established between disease severity at growth stages 10–1 and 11–1 and the mean yield per head, 1000 grain weight and sieving index.
Relations of carrot red leaf and carrot mottle viruses with their aphid vector, Cavariella aegopodii
Authors: ELNAGAR S. , MURANT A. F.
Published: February 2008

Studies with Scottish isolates of carrot red leaf (CRLV) and carrot mottle (CMotV) viruses confirmed the dependency of CMotV on CRLV for transmission by the aphid Cavariella aegopodii. CMotV was transmitted by aphids only when the two viruses were present in the same source plant, and its transmission was not assisted by anthriscus yellows virus, which acts as a helper for parsnip yellow fleck virus. Some test plants became infected with CRLV alone, and a few with CMotV alone. In winter, aphid transmission of CRLV and CMotV was greatly increased when the source plants received supplementary lighting whereas the CMotV infectivity of sap was not increased.

C. aegopodii acquired CRLV and CMotV after minimum acquisition access times of 30 min and inoculated them after minimum inoculation access times of 2 min. There was a minimum latent period of 7–18 h. The viruses were retained by the aphid after moulting and are therefore circulative in the vector, but were not transmitted to progeny insects. Aphids allowed 24 h to acquire the viruses continued to transmit them for at least 12 days, but some aphids allowed 6 h or less for virus acquisition ceased to transmit after 3 or 4 days. CRLV is considered a tentative member of the luteovirus group.
Further work on the genetics of race specific resistance in lettuce (Lactuca sativa) to downy mildew (Bremia lactucae)
Authors: JOHNSON A. G. , LAXTON SUSAN A. , CRUTE I. R. , GORDON PAMELA L. , NORWOOD JUDITH M.
Published: February 2008

Data are presented on the segregation of resistance to four races of Bremia lactucae in the F2 progenies of crosses involving 15 resistant and various susceptible lettuce cultivars. Most of these data and those recently published by other workers fit the systematic model for the genetics of race specific resistance to B. lactucae proposed by Crute & Johnson(1976).

Seven different dominant resistance genes of major effect were found. There was also evidence of a pair of dominant genes with complementary effect, one of which may sometimes be effective on its own. Two of the genes may be linked and another may have two different alleles for resistance at the same locus. The resistance conferred by these genes is specified in relation to two British, two Dutch and four French races of the fungus. Resistance genotypes are proposed for 16 cultivars.
Studies on plant growth‐regulating substances
Authors: TAYLOR H. F. , WAIN R. L.
Published: February 2008

3‐(3,5‐Dichlorophenoxy)butyric acid and 2‐(3,5‐dichlorophenoxy)ethylamine were both shown to exert pronounced dwarfing effects on tomato seedlings. Examination of extracts of the treated plants revealed the conversion of these compounds to 3,5‐dichlorophenoxyacetic acid (3,5‐D) and it is concluded that the physiological activity shown in each case depends on such a conversion to 3,5‐D within the tissues.
Insecticide resistance in damson‐hop aphid, Phorodon humuli in commercial hop gardens in Kent
Authors: MUIR R. C.
Published: February 2008

From 1966 to 1976, samples of Phorodon humuli were collected annually from five commerical hop gardens in Kent and from other hop gardens where problems in control occurred. A susceptible stock was obtained from wild hop growing in northern England in 1969. The samples were cultured in isolation on potted hops and bioassayed against insecticides in common use. The level of resistance to demeton‐S‐methyl was c. 10X in 1966 after 10 yr use, and more than doubled from 1968–1974 apparently due to the spread of a more resistant type; there was a further increase to c. 50X in 1975–1976. There was also resistance of C. 20–30X to omethoate, 2–7X to methidathion and 4–8X to methomyl. Assays and field results show an increased resistance to methidathion and less certainly to methomyl after 5 yr use. There was no clear change in response to endosulfan. The LC50's estimated from a single dose and a mean probit slope were found to agree satisfactorily with the LC50's calculated from serial doses and so should be adequate for monitoring trends in resistance.