bluuebunny/crossref_metadata_2025 huggingface dataset:
Virus diseases of celery in England
Authors: PEMBERTON A. W. , FROST R. R.
Published: February 2008

Abnormal celery plants (Apium graveolens) with symptoms typical of virus infection were collected from 28 farms in Cambridgeshire, Lancashire, Lincolnshire, and Norfolk; six different diseases were found. The causal viruses from three of these were isolated and partially characterised. Cucumber mosaic virus was quite common, but usually symptomless; it had no effect on the growth of four celery cultivars in field trials. Celery virus 036 was serologically related to western celery mosaic virus, had a host range apparently confined to Umbelliferae, and was very common in the Fens, causing ringspot symptoms in some cultivars and a loss in yield of up to 24%. This disease was much less severe than that caused by an American isolate of western celery mosaic virus in glasshouse comparisons. Celery virus 065 (an unidentified isometric virus, 28–30 nm in diameter) was less common, had a very wide host range, and caused stunting, necrosis, and chlorotic flecking in all cultivars with a loss in yield of up to 45%. Of the remaining three diseases, celery yellow spot was common; the causal agent was transmitted by mechanical inoculation, but very inefficiently, and although yield losses were not determined accurately, they were thought to be insignificant. While plants with symptoms typical of celery yellow net and celery strap leaf diseases were often found, no viruses could be isolated from them, despite repeated attempts.
A field study of the pattern of local spread of ryegrass mosaic virus in mown grassland
Authors: HEARD A. J. , CHAPMAN P. F.
Published: February 2008

In a field experiment at Hurley, small areas of old ryegrass sward, known to be infected with ryegrass mosaic virus (RMV) were partially surrounded by newly‐sown Italian ryegrass. The experiment was harvested by mowing on five occasions. Samples of Italian ryegrass taken when it was 11 months old showed a very marked increase in the levels of RMV close to the areas of old sward. Thus, 84% of the Italian ryegrass plants bordering the old sward to the north contained RMV, compared with 63% of plants only 2.7 m away. The corresponding values to the south were 68% and 39%. The much higher values encountered to the north are presumed to be caused by the movement of the mite vector of RMV (Abacarus hystrix) in relation to the prevailing wind.

Two different mowers were used, a rotary mower and a reciprocating knife mower. We could demonstrate no increase in the level of RMV as a result of mowing from the infected sward and on to the new sowing and could demonstrate no difference in the infection levels as a result of using the different mowers.

We conclude that in mown swards migration by the mite is responsible for all or nearly all of very local spread of RMV.
The effect of potato trap crops and fallow on decline of Globodera rostochiensis
Authors: LAMONDIA J. A. , BRODIE B. B.
Published: February 2008

The effects of 1 to 6 wk growth of resistant and susceptible potato cultivars on Globodera rostochiensis population decline were studied in pot and microplot experiments. In pot experiments, potato plants were hand pulled or killed with glyphosate herbicide at weekly intervals for 4 or 6 wk after shoot emergence. In microplot experiments, potato plants were killed with glyphosate herbicide weekly for 4 wk after shoot emergence. After 4 wk the number of viable eggs had declined more in pots where potato plants were grown (66–87%) than in pots of fallow soil (35%). Although decline in numbers of viable eggs under resistant and susceptible cultivars did not differ significantly, there was a trend towards greater decline under resistant plants. Duration of plant growth was positively correlated with decline in viable eggs when plants were killed with glyphosate but not when they were hand pulled. However, in microplot experiments using glyphosate, decline in viable eggs after 1 wk of potato plant growth (55%) was not different from that after 4 wk (57%). Numbers of viable eggs in fallow soil declined less 5 cm deep (34%) than 15 cm deep (50%). All of the viable eggs contained in cysts on the soil surface died within 5 months, probably due to high temperature.
Field assessment of the effectiveness of a barley yellow dwarf virus resistance gene following its transference from spring to winter barley
Authors: PARRY A. L. , HABGOOD R. M.
Published: February 2008

Resistance to infection by barley yellow dwarf virus (BYDV) has been transferred to the winter‐hardy barley cv. Vixen. The effects of various sowing and inoculation dates on this resistance have been studied at two levels of BYDV infection. At levels most likely to be encountered in the field cv. Vixen suffered only slight yield losses and even under the most extreme conditions consistently yielded more than the susceptible cv. Igri. Comparison of the range of measurements used to determine the effects of BYDV infection showed that assessment of resistance to BYDV in field‐grown winter barleys is most reliably based on yield measurements.
The influence of plant density and position in field trials designed to evaluate the resistance of carrots to carrot fly (Psila rosae) attack
Authors: ELLIS P. R. , FREEMAN G. H. , DOWKER B. D. , HARDMAN J. A. , KINGSWELL GAIL
Published: February 2008

The results of field trials designed to evaluate the resistance of carrots to carrot fly (Psila rosae) attack were influenced by plant density and position within trials. Five trials are described, their results analysed and implications for future work discussed. Density effects were of major importance when the range of densities within a trial was greater than about three‐fold. Density and damage were associated, carrot cultivars and families with the most roots having the least damage; plant densities achieved should therefore be as close as possible to the targets set. Positional effects were often very important, so trials should ideally have no more than about 10 plots in a block, possibly by using an incomplete block design. Conventional analyses of variance removing block effects may be sufficient but it is desirable, especially with large blocks, to use some form of nearest neighbour analysis for which the various possible techniques gave similar results.
Incidence of endophytes in seeds from collections of Lolium and Festuca species
Authors: LATCH G. C. M. , POTTER L. R. , TYLER B. F.
Published: February 2008

Seeds from 53 of 64 collections of Lolium perenne from its centre of origin or from old pastures in Europe were found to be infected with endophyte whereas only four of 16 commercial cultivars had infected seed. Almost two thirds of seed samples of L. multiflorum, Festuca arundinacea and F. pratensis collected from plants growing in the wild in Italy contained endophyte but none of the eight commercial cultivars of L. multiflorum and only two of five cultivars of Festuca spp. produced by the Welsh Plant Breeding Station were infected. At least one seed sample from each of six species and varieties of annual ryegrasses contained endophyte mycelium. Endophytes in annual ryegrasses could not be cultured axenically and are probably a different species to the Acremonium lolii present in L. perenne. A correction to the spelling of the specific epithet of A. lolii is explained.
Initial incidence and development of red core of strawberry
Authors: MONTGOMERIE ISABEL G. , KENNEDY DIANA M.
Published: February 2008

The initial incidence of the disease caused by Phytophthora fragariae in healthy stock of strawberry, cv. Merton Princess, was not affected by different systems of cultivation or by no cultivation for several months before preparing infested soil for planting.

In disease development studies, healthy plants which were planted in infested soil in April and sampled at 35‐day intervals showed symptoms of red core on 1 September. Disease severity (mean % number of diseased roots) increased with time and, when averaged over intervals of 70 days, the greatest increases occurred between the end of July and the beginning of October and between December and February. Whereas the former was due to infection of plants in which the total numbers of new roots were low, the latter was due to an increase in the numbers of diseased roots. Most primary roots were produced in October and early November and 75% of the final total were formed by 15 December.

Healthy plants of the cvs Cambridge Favourite and Redgauntlet, dug from the field at monthly intervals and challenged with zoospores, were less susceptible in May and June than in other months.

It is suggested that a fungicide applied in late September or October would protect the maximum number of new roots and achieve the optimum effect for a single application.
Effects of fungicide treatments and variety on development, grain growth and yield of spring barley
Authors: WRIGHT D. , HUGHES LI. G.
Published: February 2008

The effects of four fungicide treatments for the control of mildew on spring barley were assessed in three field experiments, one in each of the years 1981, 1982, 1983. The fungicide treatments (+/ ‐ triadimenol seed treatment and +/ ‐ triadimefon foliar spray applied during early booting) were chosen to control mildew, and hence affect yield determining processes, at different times in the life of the crop. Two of the experiments also tested different nitrogen amounts and the third tested four varieties differing in their degree of mildew resistance. Mildew appeared too late to affect the production and survival of spikelets and shoots, but reduced average grain weight by reducing the rate of grain growth. Grains in the upper part of the ear had a considerably lower growth rate and final weight than grains in central and basal positions but there was no evidence that the effects of mildew on grain size depended upon grain position within the ear. Mildew incidence increased with increasing nitrogen and varietal susceptibility but there were few significant interactions between these factors and fungicide treatment for grain yield. The degree of mildew control achieved by the seed treatment varied with barley variety. Use of the two successive fungicide treatments did not yield more barley than use of either alone. Amongst varieties, grain positions within the ear and fungicide treatments there was a close correlation between rate of grain growth and final grain weight. Duration of grain growth was not related to rate of grain growth or final grain weight but was inversely correlated with mean temperature during the period of rapid grain growth. The temperature sums during the period of rapid grain growth were similar for the three years and it is suggested that a more precise knowledge of the relationships between mildew incidence, varietal susceptibility and rate of grain growth may enable more accurate predictions to be made about likely yield responses to fungicide treatments.
Effects of potato genotype, oxamyl and the numbers of potato cyst‐nematodes, Globodera rostochiensis or G. pallida on tuber yields and nematode increase
Authors: WHITEHEAD A. G. , TITE D. J. , FRASER JANET E. , NICHOLS A. J. F.
Published: February 2008

A new technique is described for establishing different numbers of the potato cyst‐nematode Globodera rostochiensis in field soil, which leaves the soil homogeneous in nutrient status. Field plots established in this way were used to compare yield losses in four potato cultivars (Maris Piper, Pentland Crown, Pentland Dell and Désirée) associated with different numbers of G. rostochiensis. Over the range of 7.4 to 148.4 eggs g‐1 soil at planting, yield losses were 18.7% (Maris Piper), 53.2% (Désirée), 55.7% (Pentland Crown) and 63.5% (Pentland Dell). Similar results were obtained in another experiment on the same field in a different year using only lightly and heavily infested plots. Treating the seedbed soil with oxamyl before planting prevented significant injury to potatoes by G. rostochiensis but increased the yield of Pentland Dell and perhaps Désirée (but not Maris Piper or Pentland Crown) more than expected from nematode control alone. Treating heavily infested soil with such a nematicide cannot therefore be recommended as part of a valid procedure for establishing lightly and heavily infested plots for comparing tolerances of attack by potato cyst‐nematodes in a range of potato genotypes.

In peaty loam soils moderately or heavily infested with G. pallida, oxamyl at 5.6 kg a.i. ha‐1 incorporated into the seedbed before potatoes were planted generally increased tuber yields, though the effects varied considerably with the cultivar grown. Increase of G. pallida in these soils was controlled better by growing potatoes bred for resistance to it (ZB 35 – 29, Caxton, Santé, Morag, 11233 ab 22, Fingal, A27/23, Cromwell). Increase of G. pallida on susceptible cultivars varied greatly and Romano increased G. pallida no more than the resistant Morag. G. pallida is probably controlled best in peaty loam by growing a resistant cultivar in soil treated with a granular (non‐fumigant) nematicide.
The relationship between the entry of isoproturon into Alopecurus myosuroides and its effect on growth and CO2 fixation
Authors: BLAIR A. M.
Published: February 2008

Alopecurus myosuroides (blackgrass) was grown in nutrient and with isoproturon added to the solution when plants had three leaves. The transpiration stream coefficient factor was calculated over a period of 96h after treatment to be approximately 1. On this basis isoproturon entry into A. myosuroides was estimated using data for water loss through plants and there was a linear relationship between herbicide entry and plant weight 14 days after treatment. Treatment for at least 7 days with isoproturon at a dose of 1 μg a.i./15 ml nutrient solution (≡ 0.32 × 10‐6M) before returning plants to fresh nutrient was necessary for damage to be still evident after 14 days. This time period corresponded with the reduction of CO2 exchange to zero as measured by infra‐red gas analysis. Some recovery occurred from 6 h treatment with 120 μg a.i. isoproturon/15 ml nutrient solution when assessed after returning plants to untreated nutrient for 14 days. A quicker depletion in CO2 uptake by blackgrass occurred when both the primary and secondary roots were treated compared with secondary alone but eventually the levels reached were similar. The ‘CALF’ model predicted much higher concentrations of isoproturon than appeared necessary to damage A. myosuroides. This suggests a major influence of climate on the plant and this and other interactions are discussed.
Assessment of horizontal resistance to late blight of potatoes
Authors: SIMMONDS N. W. , WASTIE R. L.
Published: February 2008

Ten potato clones were assessed for horizontal resistance to late blight in the foliage, in replicated plots for 4 years. Plots were scored on several occasions each year and this paper explores the most reliable ways of using the data to detect differences between clones. Using the genetic component of variance (heritability in the broad sense, h2) as criterion, mean resistance over all scoring dates was found to be the best measure out of several tried. Though good discrimination was achieved within years (mean h2 > 90%), there were large clones × years interactions and changes of rank order such that h2 fell to about 65% over seasons, and many years of testing would be required to discriminate between similar clones. There was no reason to think that the interactions were caused by the erratic expression of R genes, though one case of vertical resistance was detected. Some results from parallel testing of diverse potato breeding materials are described, and implications for breeding methods and objectives are briefly discussed.
Etiology and control of durian foliar blight and dieback caused by Rhizoctonia solani
Authors: KWEE LIM TONG , CHONG NG CHING , LAN CHIN CHIEW
Published: February 2008

Foliar blight and dieback of durian seedlings and trees in Peninsular Malaysia was found to be caused by Rhizoctonia solani (teleomorph ‐ Thanatephoms cucumeris) The fungus grew well and produced abundant sclerotia at temperatures higher than 24°C with an optimum at 28°C. It grew poorly at 35°C and did not grow at 10°C. The strains studied were found to belong to the anastomosis group AG‐1. They were pathogenic on durian, papaya, cucumber, long bean, Mikania weed, padi, musk melon, mung bean, Zoysia grass, Bermuda grass, and St Augustine grass. They were mildly pathogenic on groundnut, and non‐pathogenic on maize, guava and Brassica‘pak choy’. The disease was effectively controlled by foliar sprays of pencycuron and benomyl; triadimefon and an antagonistic bacterium suspension treatment were less effective and quintozene‐etridiazole mixture gave poor disease control.
Variation in pathogenicity among field isolates of Phoma exigua var. foveata
Authors: BAIN R. A. , LENNARD J. H. , WASTIE R. L.
Published: February 2008

Experiments carried out using a point inoculation method to infect potato tubers with Phoma exigua var. foveata demonstrated considerable variation in pathogenicity among field isolates. This variation was unlikely to be due to differential reductions in isolate pathogenicities during axenic culture. However, fresh field isolates generally produced larger lesions than stored isolates. An investigation of the distribution of pathogenicity variation in the fungus revealed that differences among isolates from different lesions taken from the same potato stock were greater than those between stocks, but pathogenicity variation within each lesion isolate was small relative to that between isolates. The importance of using isolates with a high level of pathogenicity, hence recent field isolates, in studies of this pathogen is stressed.
Long‐range aphid transport hypothesis for maize dwarf mosaic virus: history and distribution in Minnesota, USA
Authors: ZEYEN R. J. , STROMBERG E. L. , KUEHNAST E. L.
Published: February 2008

In 1977 a sudden and dramatic epidemic of maize dwarf mosaic virus (MDMV) struck commercial fields of sweet corn in Minnesota causing multi‐million dollar losses. The epidemic was unusual in that MDMV historically had been confined to the southern United States and Ohio River Valley with only occasional occurrences reported from states bordering Canada. An extensive 5‐yr study of MDMV in Minnesota revealed a low incidence of MDMV from 1978 ‐ 81, and commercial fields badly infected in 1977 were not again infected. No evidence of wild host plants was found, neither was seed transmission in maize considered to be important, and MDMV strain ratios changed from year to year as did the distribution of infected fields. Concomitant studies on aphid retention revealed that MDMV could be retained by aphid vectors for more than 19 h, and that the 1977 epidemic was associated with a weather pattern that could be linked to potential aphid transport from the southern Great Plains of North America. All circumstantial evidence led to a long‐distance aphid transport hypothesis. This may be worth considering whenever unexpected epidemics of aphid‐transmitted non‐persistent viruses occur in regions where the particular virus is not endemic, and may also explain the widespread distribution of certain aphid‐transmitted non‐persistent viruses.
Use of monoclonal antibody to potato leafroll virus for detecting groundnut rosette assistor virus by ELISA*
Authors: RAJESHWARI R. , MURANT A. F. , MASSALSKI THE LATE P. R.
Published: February 2008

Three of 10 monoclonal antibodies (MAbs) produced to potato leafroll luteovirus (PLRV) were found to react in triple antibody sandwich ELISA (TAS‐ELISA) with groundnut rosette assistor luteovirus (GRAV), though none reacted with four other luteoviruses (barley yellow dwarf, bean leaf roll, beet western yellows or carrot red leaf)‐ The most effective PLRV MAb, SCR 6, was used in TAS‐ELISA to detect isolates of GRAV from groundnut plants with chlorotic, green and mosaic forms of rosette from Nigeria and Malawi. The test also detected GRAV in extracts of single Aphis craccivora.
Oxidising activity in root extracts from plants inoculated with virus or buffer that interferes with ELISA when using the substrate 3,3‘, 5,5’‐tetramethylbenzidine
Authors: JONES A. T. , MITCHELL MARGARET J.
Published: February 2008

In indirect ELISA using protein A‐horseradish peroxidase (HRP) as enzyme conjugate and 3,3′, 5,5′‐tetramethylbenzidine (TMB) as substrate, extracts of roots of all cucumber, Chenopodium quinoa and Petunia hybrida plants previously inoculated with virus or buffer produced A450 values up to seven‐fold greater than those for comparable shoots or for extracts of roots from undisturbed, uninoculated plants, irrespective of the virus antiserum used for detection. This effect was also produced in tests in which no HRP conjugate was used, indicating that root extracts from virus‐infected or physically injured plants, but not healthy uninjured plants, contain high levels of a factor able to oxidise TMB. The HRP conjugate/TMB substrate version of ELISA is therefore not reliable for detecting viruses in root extracts of herbaceous plants. In contrast, non‐specific reactions were not obtained with root extracts, and viruses were reliably detected, when protein A‐alkaline phosphatase was used as conjugate and p‐nitrophenyl phosphate as substrate.
Variation in the development of stem nematodes, Ditylenchus dipsaci, in susceptible and resistant crop plants
Authors: WHITEHEAD A. G. , FRASER JANET E. , NICHOLS A. J. F.
Published: February 2008

Dicotyledonous plants were reliably inoculated with stem nematodes by placing drops of 1.3% carboxymethylcellulose containing the surface sterilised worms between the cotyledons or in the leaf axils of recently emerged seedlings raised in pots of cool, moist soil. Inoculating onion leaves, bean stems and potato tubers or potato leaves gave variable results and inoculating onion, tulip and narcissus bulbs and lucerne and red clover stems was usually unsuccessful. An attempt to characterise 67 stem nematode populations by the reactions of a number of different plants failed for lack of useful differential hosts. Lucerne was, however, resistant to all but lucerne populations.

Multiplication of stem nematode populations varied greatly between cultivars of lucerne or red clover. Some cultivars were resistant to some populations of lucerne or red clover stem nematodes and susceptible to others. These differences could not be ascribed to differences in viability of the nematodes or to differences in success of the inoculations. They indicate the presence of different pathotypes or biotypes in different populations of a so‐called ‘host race’ and indicate the need for new resistant cultivars to be tested against a range of populations before they are released for general use. Amongst lucerne cultivars tested, Vertus was resistant to some lucerne stem nematode populations and susceptible to others. The supposedly resistant lucerne cultivars Euver and Lifeuil were as susceptible as was Europe. Amongst red clover cultivars tested, Redhead, Kühn, Changins and Mt Calme were susceptible, Britta, Lucrum and Temara were the least resistant, Renova, Rittinova and Quin were intermediate and susceptible to one or more of the populations tested but Norseman and especially Sabtoron were very resistant.
Transfer of polygenic resistance to ryegrass mosaic virus from perennial to Italian ryegrass by backcrossing
Authors: WILKINS P. W.
Published: February 2008

Polygenic resistance to ryegrass mosaic virus (RMV) was transferred from perennial to Italian ryegrass cv. Tribune by repeated cycles of backcrossing, polycrossing and selection. The resulting synthetic variety (Bb 2113) was highly resistant to infection by RMV whereas the Italian ryegrass cultivars Tribune, RvP, Bartolini, Augusta, Wilo and Dalita all were highly susceptible. Leaf width and length of Bb 2113 was similar to that of cv. Tribune and, like Tribune, Bb 2113 had awned florets. In a field trial, Bb 2113 had a similar persistency rating and number of inflorescences in the regrowth to cv. Tribune but produced 11% less dry matter. The results emphasise the need for a more efficient means of transferring small numbers of genes from one species of Lolium to another than backcrossing provides.
Susceptibility of mushroom pests to the insect‐parasitic nematodes Steinernema feltiae and Heterorhabditis heliothidis
Authors: RICHARDSON P. N.
Published: February 2008

The potential of two species of insect‐parasitic rhabditid nematodes (Steinernema feltiae, Heterorhabditis heliothidis) for biological control of mushroom flies was studied in pot trials. Three Diptera that commonly infest mushroom crops were used; the larvae of Megaselia halterata (Phoridae), Heteropeza pygmaea (Cecidomyiidae) and Lycoriella auripila (Sciaridae) were all susceptible to parasitism by both nematode species. Fewer adult phorids and sciarids emerged when compost was nematode‐treated and, for L. auripila, the effects of nematode applications at spawning, casing or on both occasions were compared. Casing treatments were more effective than spawning treatments; little extra benefit was gained from applying the nematodes twice. Populations of paedogenetic larvae of H. pygmaea built up rapidly in untreated compost, but were reduced when S. feltiae was applied, and were eradicated by H. heliothidis. Because they can penetrate insect cuticle, as well as natural body openings, Heterorhabditis spp. may be more suitable than Steinernema spp. for the control of mushroom fly larvae.
Resistances to oat mosaic virus in autumn‐sown oats
Authors: CATHERALL P. L. , VALENTINE J.
Published: February 2008

A total of 100 varieties and advanced lines of autumn‐sown oats were assessed for reaction to soil‐borne oat mosaic virus. Two apparently distinct types of resistance, resistance to becoming infected and post‐infection resistance, were detected. Of the named varieties tested, cv. Lustre was outstanding, possessing the highest level of resistance to infection. Several breeding lines, but no named variety, possessed outstanding post‐infection resistance. A few varieties such as cv. Solva, which lacked either type of resistance, were tolerant of the virus.
Short‐term forecasting of wheat yield loss caused by the grain aphid (Sitobion avenae) in summer
Authors: ENTWISTLE J. C. , DIXON A. F. G.
Published: February 2008

A damage model was used to take into account the effect on winter wheat yield of the size, duration and timing of Sitobion avenae infestation in summer, and the influence of insecticide applications. It was validated as far as possible using available data, and appeared to be sufficiently accurate to be useful. The model was applied to a total of 32 winter wheat fields over the period 1975 to 1983 in eastern England and the Netherlands, to obtain estimates of yield losses associated with not applying insecticides at the end of ear emergence (G.S. 59), mid‐anthesis (G.S. 65) or the end of anthesis (G.S. 69). These estimates of future yield losses were related in multiple regressions to the number of S. avenae per tiller at the time the insecticide was applied, and the rate of population increase over the previous few days.

Basing the decision about whether to apply insecticide on forecasts from the multiple regression equations appeared to be slightly more profitable than prophylactic spraying when the chemical cost alone was considered, but substantially more profitable when the application cost and wheeling loss were also taken into account. The strategy minimising losses involved forecasts at all three crop growth stages. It was validated using a further 21 fields studied in 1984 and 1985, and gave better results than the EPIPRE system, which over‐estimated the number of fields requiring spraying, and the economic threshold of George & Gair (1979), which under‐estimated the number requiring spraying. However, the accuracy of the damage model needs to be checked against measured yield losses in order to establish the success of the multiple regression strategy conclusively.
The effect of frit fly Oscinella frit on the yield and persistence of Italian and hybrid ryegrasses in the laboratory
Authors: MOWAT D. J. , JESS S.
Published: February 2008

Three cultivars of Italian or hybrid ryegrass were exposed to frit fly attack at varying frequency in the laboratory. Initially a Westerwolds and a hybrid cultivar showed greater yield reductions than an Italian ryegrass cultivar, although they did not usually suffer a higher proportion of damaged tillers. The differing effect on yield appeared to be due mainly to greater impact of first or infrequent attacks on cultivars producing fewer tillers. After two to six attacks in approximately 7 months the Westerwolds and hybrid cultivars appeared to become tolerant to attack and were subsequently the least affected, although continuing to suffer tiller damage at a rate at least as high as the Italian ryegrass. All cultivars recovered fully when attack ceased, and their exclusion from attack did not improve their persistence.
Uptake and movement of the fungicide imazalil following trunk injection into apple and plum trees by a novel, rapid technique
Authors: CLIFFORD D. R. , GENDLE P. , HOLGATE M. E.
Published: February 2008

A hand‐held apparatus, produced by modifying a veterinary multiple dosing gun, was used to pressure‐inject aqueous solutions of imazalil into the trunks of plum or apple trees after harvest, before bud burst or during flowering. Bioassay showed that post harvest injection led to movement of imazalil up and down the trunk and into branches of both apple and plum trees. Movement in the trunk after injection before bud burst also occurred in plums but was limited in apples and fungicide was detected in branches only in apples and only at the end of the season. Injection at flowering time resulted in movement of imazalil into branches of apple, but not plum, trees. Imazalil was detected in twigs of apple, but not plum, trees but only after flowering time injections.

The technique could be useful for control of tree diseases provided due attention is paid to dose, to the number and siting of injection holes and to the linking of injection time with the epidemiology of the target disease.
Comparison of bioassay and chemical determination of the activity of the fungicide guazatine as used in post‐harvest citrus dips
Authors: WILD B. L.
Published: February 2008

A bioassay procedure was developed as a means of assessing the fungicidal efficacy of post‐harvest citrus dips containing the fungicide guazatine. The method is designed to overcome certain inaccuracies associated with the existing method of chemical analysis. The technique involves assessment of actual fungicidal activity by the inhibition of growth of a Geotrichum candidum culture. Comparisons are made between results of chemical analysis and this method, and the usefulness of the procedure is demonstrated.
Competition between effective and ineffective bradyrhizobia nodulating peanuts (Arachis hypogaea)1
Authors: BYALEBEKA J. B. , WYNNE J. C. , SCHNEEWEIS T. J. , ELKAN G. H.
Published: February 2008

The competitive ability of effective and ineffective isolates of Bradyrhizobium to form nodules on four peanut (Arachis hypogaea) genotypes from which they were originally isolated was investigated in a greenhouse study. Pregerminated seeds of each genotype were inoculated with five ratios of ineffective effective bradyrhizobia: 104:0, 104:102 104:104 102:104 and 0:104. Plants were harvested 35 days after planting and nitrogenase activity, total nodule number per plant, plant shoot dry weight and the proportion of nodules formed by each Bradyrhizobium isolate were determined. Nodulation suppression occurred on plants inoculated with the mixed cultures, especially on those inoculated with the 104:102 ineffective effective inoculum ratio. More than 85% of the nodules on plants inoculated with the 104:104 and 102:104 ineffective effective Bradyrhizobium mixtures were formed by the effective isolates. The number of effective nodules per plant, nitrogenase activity and plant shoot dry matter production all increased with the proportion of the effective bradyrhizobia in the inocula.
Ice‐nucleation on kiwifruit
Authors: YOUNG J. M.
Published: February 2008

Ice‐nucleating capability of the kiwifruit vine, Actinidia deliciosa, was examined. Pseudomonas viridiflava, present as an epiphyte on the vine, was an effective icenucleating agent. The presence of other sources of ice nuclei on the surface of the vines, leaves and fruit, which could not be inhibited by anti‐bacterial agents, was also demonstrated.
Effect of osmotic priming, rinsing and storage on the germination and emergence of carrot seed
Authors: DEARMAN JANE , DREW R. L. K. , BROCKLEHURST P. A.
Published: February 2008

Carrot seed, osmotically primed in polyethylene glycol solution (273 g/kg water) for 10 days at 15°C, was given 0–5 rinsing cycles, where each cycle comprised agitating the seed in 10 times its own bulk volume of distilled water for 20 to 30 s.

Priming decreased the germination and emergence times whether the seeds were rinsed or not, and these effects were maintained even after storage for 450 days. The number of rinsing cycles had no effects, except that seed given five rinsing cycles deteriorated after 270 days storage.
Distribution of Rhopalosiphum padi (Hornoptera: Aphididae) on spring barley plants
Authors: WIKTELIUS S.
Published: February 2008

The distribution of Rhopalosiphum padi on spring barley plants in the field and the laboratory is described. Aphids fed mainly on the lower parts of the plants in both the field and the laboratory. A relatively large proportion of the field population was found beneath the soil surface early in the season. In the laboratory, aphids preferred the stem base and auricles of young and old plants respectively. The highest soluble nitrogen concentration was found in the stem base of young plants. The aphids avoided temperatures above 25°C in a temperature gradient (20°C‐40°C). The soil surface temperature in a barley stand can reach lethal levels for aphids during clear days early in the season. It is concluded that the preference of R. padi for the lower part of young spring barley plants is mainly a consequence of the stem base being the most nutritious part of the plant and that a harsh microclimate possibly forces the aphids beneath the soil surface. This tendency to feed near or below soil level must be taken into account when assessing field densities of R. padi.
The role of grasslands in the yearly life‐cycle of Rhopalosiphum padi (Homoptera: Aphididae) in Sweden.
Authors: WIKTELIUS S.
Published: February 2008

The population density of the bird cherry‐oat aphid (Rhopalosiphum padi) was monitored in spring sown barley and in grasslands (leys and pastures) and a suction trap was used to monitor the flight periodicity of the aphids. Emigrants from the primary host (bird cherry) colonised both grass and cereals in spring and a migration from cereals to grasses took place in mid‐summer. There was a negative correlation between the sizes of summer and autumn migration. There was a positive relationship between late summer growth in leys and the size of autumn migrations. It is concluded that the size of the autumn migration is mainly dependent on aphid population growth in grasslands during late summer and autumn.
Association of Phoma aquilina and Ascochyta pteridis with curl‐tip disease of bracken
Authors: IRVINE J. I. M. , BURGE M. N. , McELWEE MARION
Published: February 2008

Many spores of Phoma aquilina and Ascochyta pteridis were rinsed from dry infected litter obtained from a site where curl tip was prevalent. More spores were released from litter which had been incubated under moist conditions for 24 h before rinsing. P. aquilina, known to cause curl‐tip symptoms in bracken when inoculated via wounds (McElwee, 1983), did not damage healthy plants when spores were applied to intact tissues. A. pteridis appeared to infect undamaged plants under humid conditions causing the initial ‘fleck’ symptoms associated with the disease. Flecks formed on plants by A. pteridis may permit subsequent infection by P. aquilina.

For bracken control, treating plants with fungal inoculum in disease‐free areas may result in disease if inoculum supplements can be found which permit initial infection by A. pteridis or damage plants sufficiently to allow colonisation by P. aquilina directly.
Effects of net blotch on growth and yield of spring barley
Authors: DEADMAN M. L. , COOKE B. M.
Published: February 2008

The effect of net blotch on the growth and yield of cv. Beatrice spring barley was examined in a greenhouse experiment. Separate inoculations at growth stages 21 and 34 reduced green leaf area, root weight, leaf sheath and stem weight and tiller number. The early inoculated plants, which responded and recovered more rapidly than later treated ones, suffered a loss in grain yield and this was related to the amount of disease, the loss in green leaf area and the reduction in unit leaf rate.
Fungicidal control of Rhizoctonia solani in relation to soil texture, organic matter and clay minerals
Authors: KATARIA H. R. , SUNDER S.
Published: February 2008

In pot tests, MEMC, quintozene, captafol, carboxin, thiabendazole, carbendazim, benomyl and thiophanate‐methyl used as seed treatments gave much better control of cowpea seedling rot in light‐textured sandy and loamy sand soils than in heavy‐textured loam and silt loam soils inoculated with Rhizoctonia solani. Disease control by chloroneb was not altered by soil texture. Amendment of sandy soil with montmorillonite reduced disease control with all fungicides, except chloroneb and carboxin; similar amendments with kaolinite decreased efficacy of MEMC and captafol. Green manuring with cluster bean reduced disease control by MEMC, captafol, benomyl and thiophanate‐methyl; sunnhemp reduced efficacy of MEMC. Most fungicides gave poor disease control when farm yard manure or biogas sludge was added to soil, the sludge having the more marked effect. All the fungicides tested, except carboxin, were inactivated to different extents by humic acid extracted from farm yard manure.
Glasshouse evaluation of fungicides for the control of sunflower downy mildew (Plasmopara halstedii)
Authors: OROS G. , VIRÁNYI F.
Published: February 2008

A precise, reproducible and easy‐to‐handle glasshouse test is described for the evaluation of the systemic activity of chemicals for the control of Plasmopara halstedii, the downy mildew pathogen of sunflower. Four‐day‐old sunflower germlings were inoculated by immersing them in a zoosporangium suspension. Seedlings were then immersed in appropriate concentrations of the chemicals to be tested. Plants were grown in a glasshouse and assessed on three occasions to determine successively antisporulant, curative (systemic fungistatic), and eradicant effects.

Sporulation in general was inhibited by lower concentrations than those required to exert an eradicant effect. There was a highly significant correlation between the ED50 values for visually recognised disease symptoms (stunting, dampingsff and leaf chlorosis) and for both curative and eradicant effects.

Among 13 compounds tested, metalaxyl, RE 26745, furalaxyl, LAB 149202F and cymoxanil showed sufficient eradicant activity, to justify field evaluation for eradication of seed infections.
The effects of time of sowing and harvest on carrot biochemistry and the resistance of carrots to carrot fly
Authors: COLE ROSEMARY A. , PHELPS KATHLEEN , ELLIS P. R. , HARDMAN J. A.
Published: February 2008

Two carrot cultivars which represented contrasting levels of resistance to carrot fly, Psila rosae, were grown in a replicated field experiment at Wellesbourne in 1984–85. Seed was sown on five occasions between April and August 1984 and the crop harvested after a minimum growth in the field of 16 wk on seven occasions between August 1984 and February 1985. A highly significant correlation (r = ‐0.78; P > 0.001) between the levels of carrot fly damage and the concentration of chlorogenic acid in the roots enabled a model to be formulated to predict the relative predisposition to carrot fly larval damage; high levels of chlorogenic acid early in the season predisposed roots to severe attack when they were older.
Inhibition of degreening in the peel of bananas ripened at tropical temperatures
Authors: SEYMOUR G. B. , THOMPSON A. K. , JOHN P.
Published: February 2008

Bananas (Musa AAA Group, Cavendish Subgroup) were ripened over a range of temperatures from 15 to 35°C. The rate of ripening in both pulp and peel was accelerated with an increase in storage temperature up to about 24°C. Above this temperature the pulp softened and sweetened without the development of a fully yellow peel due to a decrease in the rate of chlorophyll breakdown. Peel carotenoid content was higher at 35°C than at 20°C.
The effects of cutting and asulam on numbers of frond buds and biomass of fronds and rhizomes of bracken Pteridium aquilinum
Authors: LOWDAY J. E.
Published: February 2008

The effects of cutting and the herbicide asulam for the control of a dense uniform stand of bracken Preridium aquilinum were investigated experimentally over a 6 —yr period in Norfolk, England. Bracken is a particularly difficult species to control by either mechanical or herbicidal means because of its extensive and complex rhizome network, containing large reserves of dry matter and a large number of frond buds. Cutting bracken in the summer removed dry matter from the system and reduced frond vigour but did not reduce the number of frond buds to a critical level. Whereas the first few cuts substantially reduced the standing crop of fronds, relatively stable standing crops of fronds were observed in future years despite continued cutting. Asulam caused a 99% reduction in the standing crop of fronds in the year after spraying, but in the absence of further treatment, fronds recovered to pre‐spray levels after 6 yr. Asulam caused severe localised damage to frond buds and rhizome apices, but otherwise the rhizome network remained intact. New sections of frond bearing rhizome (short shoots) developed on storage rhizome (long shoots) deep in the soil of both the asulam plots and those cut.
An evaluation of the potential of low temperature pre‐sowing treatments of tomato seeds as a means of improving germination performance
Authors: COOLBEAR P. , NEWELL A. J. , BRYANT J. A.
Published: February 2008

Low temperature pre‐sowing treatment of tomato seeds substantially enhanced germination rates and was much more effective at improving uniformity of germination than equivalent osmotic treatments. Although radicle emergence was inhibited by the low temperature, imbibition studies showed that seeds were maintained at lag‐phase moisture contents during treatment and some aspects of germinative metabolism began. No evidence was found for improved seedling growth rates per se as a result of pretreatment: in fact, initial axis growth may be temporarily reduced, probably as a consequence of depletion of reserves during the treatment period.
The role of parasitic nematodes and hymenopterous parasitoids in causing premature death of Oscinella spp. larvae
Authors: MOORE D. , HUNT D. J.
Published: February 2008

There was a range of severity of parasitism of stem‐borer larvae by Hymenoptera and Nematoda and much premature death of the larvae. A nematode, Panagrolaimus rigidus, normally considered to be saprophytic, was implicated in some mortality of stem‐borer larvae.
The efficacy of sex‐attractant monitoring for the pea moth, Cydia nigricana, in England, 1980–1985
Authors: WALL C. , GARTHWAITE D. G. , SMYTH J. A. BLOOD. , SHERWOOD A.
Published: February 2008

SUMMARY

The efficacy of monitoring the pea moth (Cydia nigricana) in dry‐harvested pea fields with pheromone traps was evaluated on commercial farms in Eastern England used by ADAS as back‐up monitoring sites. In particular the use of a ‘threshold’ catch to determine both the need for and timing of insecticide sprays was evaluated. Fields in which ‘threshold’ catches were achieved had more damage in unsprayed plots than fields in which there were no ‘threshold’ catches. When two sprays were applied to crops at ‘threshold’ sites, the timing of the first predicted by the monitoring system, excellent control was achieved with 85% of crops having less than 1% peas damaged, and none more than 2–3%. Incorrectly timed sprays, or even one correctly timed spray, produced erratic control.

Simple assessments of economic loss show that it is unnecessary to spray crops in which a ‘threshold’ is not achieved. Spraying ‘threshold’ crops, however, is very worthwhile and applying two sprays, the first timed with pheromone traps, will be particularly advantageous to both growers of peas for human consumption when ‘clean’ crops are at a premium, and to seed producers.

The data can be used to predict the probabilities of damage levels, assuming different control strategies.
Variation in annual and regional damage to sugar beet by pygmy beetle (Atomaria linearis)
Authors: COCHRANE J. , THORNHILL W. A.
Published: February 2008

SUMMARY

The reported amount of damage done by pygmy beetle to the sugar‐beet crop varies greatly with year and with region. Annual variation in damage is most strongly correlated with soil temperatures of the previous August, implying improved breeding success in warm summers. The value of predicting damage using this relationship is discussed. Damage is most severe in areas of intensive beet growing, particularly on low‐lying areas around The Wash.

There was no relationship between damage and the numbers caught in a 12.2 m suction trap in the spring. It is suggested that much of the damage is done by beetles which are present in the beet fields at or shortly after sowing, having arrived there before the great majority fly in May‐July.
Infection of sunflower leaves by ascospores of Sclerotinia sclerotiomm
Authors: SEDUN F. S. , BROWN J. F.
Published: February 2008

Ascospores of Sclerotinia sclerotiorum infected fully expanded sunflower leaves in the absence of added nutrients, wounds or senescent tissue. The site of infection was confined to a specific region around the junction of the leaf blade and the petiole and was associated with sites of sucrose secretion by the host. In these areas ascospores germinated and formed extensive colonies on the leaf surface. Simple appressoria were visible at 24 h, and complex appressoria at 48 h, after inoculation. Ascospores that germinated in areas where sucrose was not secreted produced germtubes that were shorter (less than 50 μm at 48 h after inoculation) than those produced at sites where sucrose was secreted (greater than 5 mm in length). Infections also developed on severely wounded main leaf veins. Leaf wetness was required for infection, with maximal infection occurring after a 72 h dew period.
The effect of temperature on the response of canes of red raspberry cv. Mailing Jewel to infection by Didymella applanata
Authors: WILLIAMSON B. , PEPIN H. S.
Published: February 2008

A single population of container‐grown red raspberry plants cv. Mailing Jewel was divided and grown in two environments prior to wound inoculating young canes with Didymella applanata in late July. The plants were then sub‐divided and held in one of three contrasting post‐inoculation environments. Various assessments were made to examine the effect on spur blight of the different environmental treatments.

Inoculation of internodes showed that D. applanta produced longer lesions and more pseudothecia on canes grown in spring in an unheated glasshouse than on canes grown outside, but post‐inoculation conditions had little effect on these aspects of disease. Petiole inoculations showed that dwarfing of axillary buds in the first season and lateral shoot failure in the year after infection were most serious on canes grown outside in spring but held at relatively high temperatures in August and September after inoculation. The results indicate that spur blight may have the potential to cause higher yield losses in areas with warmer spring and autumn conditions than those usually experienced in north‐east Scotland.