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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 32 (1983), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Equations to assist the estimation of national losses from the results of disease surveys carried out at GS75 were derived from five fungicide trials and two inoculation experiments in the field. The equations indicate that the percentage loss in grain yield is equal to 5.412xi0.6, 1.011xior 0.551xii where xi and xii are the percentage area infected on the flag and second leaves respectively.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 26 (1977), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Samples from 265–333 randomly selected crops of winter wheat in England and Wales were taken annually from 1970 to 1975 after heading, the main sample being at the milky-ripe growth stage. The percentage of the area of the top two leaves affected by diseases was recorded and, in the last five years, samples were tested for infection by barley yellow dwarf virus: in 1975 stem base diseases were recorded. Scptoria was the most common and severe disease in four of the six years. In. 1970 mildew was most severe and, in 1975, brown rust. The severity of infection by Septoria tended to be greater in southern and western areas in wetter summers and in crops following a previous cereal. Yellow rust was most severe in 1972, when it was very prevalent on cv. Joss Cambier. In 1973 the disease was less severe, but in 1974 and 1975 the severities of both yellow and brown rusts increased in association with the popularity of susceptible cultivars. There was a tendency for yellow rust to be more severe on early-sown crops. In 1975, eyespot was recorded on 11·8 per cent of the stems. 1·8 per cent of the symptoms being severe. Fungicidal sprays were associated with a slightly smaller incidence of stem base diseases. Estimates of percentage loss in yield due to particular diseases vary from almost zero caused by yellow rust in 1970 to 7·4 per cent loss caused by Septoria in 1972.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 21 (1972), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Samples from 250–300 spring-sown barley crops including all popular cultivars were taken when the grain was milky ripe. The percentage of the leaf area affected by recognizable diseases was recorded for the top two leaves and sub-samples were tested for barley yellow dwarf virus. Mildew was the most severe disease in the first three years. In 1970, brown rust was most severe. Leaf blotch was the second most severe disease in 1969; in other years it was less severe than mildew and brovm rust. Estimated losses in yield due to mildew were revised in the light of recent data on disease progress. Annual losses of 7–11 per cent, with a mean over the four years of 9 per cent were estimated. Losses caused by leaf blotch infection were estimated to have been about 1 per cent in 1967, 1968 and 1969 and nil in 1970. No consistent annual pattern of distribution of mildew between geographical regions was apparent. Brown rust and leaf blotch infection levels tended to decrease from south to north. Disease severity was related to previous cropping only with respect to leaf blotch in 1969 when crops following a previous barley crop were infected more severely than those following another crop.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 38 (1989), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Severe infection with Septoria tritici occurred in four of five experiments designed to create a series of different disease epidemics. These experiments successfully identified periods suitable for infection. They also indicated the effect of sprays, timed before and after these periods, on disease development and yield.Analysis of disease progress and weather records suggested that critical conditions for initial development of S. tritici occurred during early May at four sites. Heavy rain giving at least 10 mm on 1 day or a total of 10 mm or more on 2 or 3 successive days occurred at all four sites prior to the appearance of symptoms on a particular leaf layer, though less heavy rain may suffice to splash inoculum onto upper leaves in shorter, immature canopies where stem elongation is incomplete. At the fifth site, infection occurred later in May and disease failed to develop to a significant degree. At all sites, the length of the incubation period on any of the top three leaves was found to be between 396 and 496 degree days.Control of winter epidemics of S. tritici had little effect on yield, whereas spray sequences commencing later than growth stage (GS) 31 but immediately prior to the critical periods provided the best disease control and yield benefit. Regression models incorporating, as independent variables, area under the S. tritici disease progress curve for any of the top three leaves from their emergence (GS 32-37) satisfactorily explained yield loss at the four sites where disease was severe. Consideration of leaf 2 or leaf 3 alone accounted for more than 82% of the variance at each site and a yield loss from infection of leaf 2 related to thermal time is suggested as 0.00265% per C per day from the appearance of symptoms.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 37 (1988), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An experiment started in spring 1979 tested the effects of different treatments to perennial ryegrass, established as pure stands or undersown in spring wheat, on the severity of septoria diseases on the grass and in a following crop of winter wheat, sown in autumn 1980. Other plots were fallowed in 1979 and 1980 before sowing to winter wheat, also in autumn 1980. Septoria tritici was most severe in winter wheat after fallow and least severe in wheat that had been direct-drilled after ryegrass. These effects were attributed to differences in amounts of available nitrogen, and consequent differences in crop growth, rather than to any differences in primary inoculum.Symptoms attributed to S. nodorum on the ryegrass were more common where the grass had been established under spring wheat than where it had been sown as a pure stand. They also tended to be more common where ryegrass had been inoculated with spores of S. nodorum than where it had been sprayed with captafol. Similar effects on symptoms attributed to Septoria spp. (mostly S. tritici) on the wheat were apparent in July. The results support the conclusion that the greater severity of septoria diseases that often occurs on wheat after grass than after non-graminaceous breaks, is probably due in part to survival of the pathogens on grass and, in some circumstances, on debris remaining from a previous wheat crop. However, other factors are also likely to be involved.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 25 (1976), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In observations made over four seasons, counts of brown rust spores trapped above barley crops and infections of healthy plants placed within crops, indicated that there was a high risk of infection on days when at least 5 far of dew were recorded following a day on which the maximum temperature was greater than 15°C. In spray-timing trials, the fungicidal sprays applied between the first appearance of brown rust in the crop and the beginning of the exponential phase of the epidemic usually were associated with the highest yields. The relationships between levels of brown rust and yields in these trials is discussed in connection with their relevance to the estimation of losses caused by the disease.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 22 (1973), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The development of powdery mildew of barley was studied during May and June in 1971 and 1972. Spore trapping data, and experiments involving the exposure of mildew-free plants in a barley crop, established that periods when there was a high incidence of infection, with subsequent disease development, generally coincided with days on which large numbers of Erysiphe conidia were trapped above the crop. Meteorological criteria are described which have detected high risk infection periods for the two years under consideration.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 26 (1977), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In field experiments with winter wheat in Hertfordshire, seed infection with Septoria nodorum and the incorporation of infected straw into seedbeds were often correlated with reduced seedling establishment and increased seedling infection. Artificially infected straw was a less effective source of inoculum than naturally infected straw, which gave rise to the most severe leaf symptoms in one season when heavy rain favoured the development of an epidemic. In an experiment where a severe epidemic did not develop, organomercury seed treatment was the most important factor increasing seedling emergence and grain yield, also apparently leading to decreased Septoria infection of the flag leaf sheath. Spores from lesions which developed after plots were sprayed with a suspension of pycnidiospores of S. nodorum were not always morphologically typical of that species.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 25 (1976), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Single stems of winter wheat cv. Maris Templar were selected at random along traverses of primary foci of yellow rust (Puccinia striiformis Westend) in a commercial crop. Severity of the disease was recorded as the percentage area affected on the flag and second leaves at the milky-ripe growth stage. The ears were harvested when ripe and threshed individually. Grain weight per ear and mean weight of single grains were negatively correlated with disease severity, but there was no significant relationship with the number of grains per ear. The co-efficient of linear regression of percentage loss on flag leaf rust severity were 0.41 and 0.39 for equations based on single grain weight and total yield per ear respectively. Transformation of percentage yellow rust by exponents of 1.2 and 1.35 led to co-efficient of 0.18 and 0.09 respectively for the regression of percentage loss in single grain weight and yield per ear on disease level.I am indebted to Mrs. P. A. Waples, Miss N. Parsons and Messrs. R. W. Polley, J. G. Waples and J. D. S. Clarkson for their invaluable help in obtaining the data for this work.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 26 (1977), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Randomly selected crops of spring barley in England and Wales were sampled annually in July, when the grain was filling most rapidly, and the diseases affecting the flag and second leaves were assessed. Mildew was the most common disease in all years and was the most severe disease on both leaves, except in 1975 when it was slightly less severe on the flag leaf than yellow rust. Other frequently recorded diseases were brown rust, leaf blotch and, in 1972, 1973 and 1974, Septoria spp. Halo spot and net blotch were infrequent and generally not severe. Fungicides, applied as a seed treatment or foliar spray, were used on up to 47 per cent of the crops assessed and were associated with a decreased severity of mildew. It is estimated that in 1974 and 1975 at least 60 per cent of the crops which received no fungicide would have given an economic yield increase following treatment for mildew control. Annual estimates of national yield losses caused by mildew varied from 5·7 to 13·0 per cent: much greater than the 0·2 to 1·7 per cent estimated for brown rust or leaf blotch. Barley yellow dwarf virus was detected by transmission tests in the majority of the samples tested.
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