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With the threat of certain plant protection products becoming ineffective due to reduced pathogen sensitivity to fungicides or through the removal of products due to changes in legislation, alternative compounds are sought for use in disease management programmes. The effects of an arabinoxylan film-forming polymer derived from maize cell walls to control crop diseases of spring barley was assessed in field experiments. Control of powdery mildew, Rhynchosporium scald, and Ramularia leaf spot on barley was achieved with the polymer but control was inconsistent between trials. However, good levels of disease control were observed when the polymer was applied with a reduced fungicide programme. No yield penalties were associated with use of the polymer in any trial irrespective of the level of disease control. Alternative plant protection products such as this arabinoxylan polymer may be useful components in future integrated disease management strategies aimed at reducing fungicide inputs without any cost to disease control.

Field experiments were conducted over two years to quantify the yield response to fungicide of spring barley ( Hordeum vulgare L.) genotypes differing in disease severity and canopy structure. Fourteen genotypes were selected from a doubled-haploid mapping population to represent three distinct canopy phenotypes; tall with prostrate leaves, medium height with prostrate leaves and medium height with erect leaves. The fungicide treatments were based on a triazole plus strobilurin and chlorothalonil programme applied at the start of stem extension and during booting. Untreated plots served as controls. The major foliar diseases and disorders were powdery mildew and brown spotting in 2006 and powdery mildew, rhynchosporium barley leaf blotch and brown spotting in 2007, and genotypes differed significantly in the severity of each. Fungicide reduced powdery mildew and rhynchosporium symptoms in susceptible genotypes, but had little effect on spotting. The yield response to fungicide averaged across genotypes was approximately 1 t ha −1 and there was no significant difference in response between canopy types or genotype. The increase in yield was mostly via an increase in grain numbers m −2 with smaller or non-significant effects of fungicide on mean grain weight. When effects of fungicide on radiation interception were plotted against those on yield, a yield response of 0.8–1.4 t ha −1 was indicated in the absence of visible disease. The results show that the effects of fungicide treatment on grain numbers cannot be explained just in terms of protection of green area and increase in radiation interception. Nor were they the result of a delay in leaf senescence. Other possible explanations include control of symptomless infection at critical developmental stages, or direct effects of fungicides on plant metabolism. These findings have important implications for fungicide stewardship and disease management in barley, because the requirement for fungicide, as defined in terms of the likely yield response of the crop, cannot be predicted just from an assessment of the amount visible disease present or the risk of a disease epidemic developing.

Cereal farming is moving rapidly towards reduced tillage, with over 100 million ha of land currently tilled using minimum tillage implements. This study reports five years of data from a field experiment investigating the response of different barley cultivars and mixtures to soil tillage practice and nitrogen fertiliser levels. Five tillage treatments were established that imposed different amounts of soil disturbance: (T1) zero tillage, (T2) minimum tillage to 7 cm depth and ploughed treatments followed by power harrowing consisting of (T3) conventional plough to 20 cm depth, (T4) plough to 20 cm followed by compaction by wheeling the entire plot with a tractor fitted with 8.8 Mg total load and (T5) deep plough to 40 cm depth, all on the same site each year. Four winter barley cultivars (Sumo, Fanfare, Pastoral and Pipkin) were selected based on contrasting rooting characteristics, disease resistance and yield sensitivity. They were planted in plots as monocultures and as all 2-, 3- and 4-component mixtures thereof. Significant differences in soil physical properties and carbon content were observed over the five years of the study. Grain yield varied by 13% between tillage treatments, with conventional and deep plough conditions generally the highest yielding and zero tillage the lowest. Sumo gave the highest yield overall under deep plough conditions, whereas Pipkin was the best cultivar under conventional and zero tillage conditions. Rhynchosporium was the most common disease and the mixture gave decreased infection in all years and tillage conditions. Complex mixtures gave around 32% less disease than the simple mixtures. There was an overall differential cultivar response to soil tillage conditions that was buffered by cultivar mixtures. Mixtures offered benefits in both yield response and disease control under all soil tillage conditions.

The effects of field-trial scale, including plot size, and its interaction with fertiliser level and barley germplasm on mixture efficacy in controlling powdery mildew were investigated. Two groups of cultivars, one from cultivars grown in the UK and the other from cultivars grown in Poland, along with all their respective three-component mixtures, were grown in three field trials, one with 13.5 m 2 plots, one with 0.4 m 2 plots, and the third in intermediate size plots, which included a mixture of all the cultivars in both groups in equal size treatments of structured spatial arrangements. Another trial utilised similar structured spatial arrangements to trial 3 was carried out using a combination of cultivars with appropriate matching virulence levels (trial 4). Mixtures showed either a reduction in powdery mildew infection compared with the component monoculture mean, or no significant effect. There was a trend towards greater reductions at the low fertiliser level and smaller plot size. The most structured spatial arrangement was most effective for reducing infection in trials 3 and 4, but the complex-homogeneous arrangement in the fourth trial was also effective. Rhynchosporium was reduced by a similar and substantial amount by both spatial treatments in trial 3. The plot size and structuring effects may be explained by the interaction between host heterogeneity structure and pathogen dispersal scale effects, but resource exploitation for yield was best in the complex-homogeneous arrangement in trial 3 where all components were present to respond directly. These findings have implications for methods of trialling mixtures for large-scale field use and for testing component combining ability.

The phytopathogen Rhynchosporium alismatis occurring on Alisma, Sagittaria and other genera in the Alismataceae is under investigation as a mycoherbicide for alismataceous weeds in Australian rice crops. The type species of Rhynchosporium, R. secalis belongs in the Helotiales while the phylogenetic relationships of R. alismatis were unknown. To identify fungi related to R. alismatis the internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1, 5.8S rRNA gene, ITS2) of 56 isolates was sequenced and compared to those available in databases. Analysis of ITS sequences revealed close relationships between R. alismatis and the teleomorph genus Plectosphaerella as well as several anamorphic fungi which were primarily species of Verticillium. Rhynchosporium alismatis and Plectosphaerella cucumerina clustered together with 98% bootstrap support. Morphological comparisons supported this relationship indicating that R. alismatis and the anamorphic genus Plectosporium are congeneric. Rhynchosporium alismatis is transferred to Plectosporium a name proposed for conservation.

To prolong the effective life of the newer, more active DeMethylation Inhibitor (DMI) fungicides, two-spray programmes were evaluated for their effectiveness in combining good control of rhynchosporium on winter barley with prevention of the build-up of DMI-resistant pathogen strains. Programmes were based on the DMI epoxiconazole alone or in combination or alternation with three partner fungicides with different modes of action, fenpropimorph (a morpholine), cyprodinil (an anilinopyrimidine), azoxystrobin (a QoI/strobilurin fungicide). In the majority of six field trials in Northern Ireland and South-west England (1998–2000), DMI sensitivity of Rhynchosporium secalis isolates was lower after fungicide treatment than before and the least sensitive isolates came from the plots treated with two half-rate applications of epoxiconazole alone. All fungicide programmes reduced disease compared with the untreated control. Epoxiconazole used alone gave the poorest disease control, but did increase the yield. The three partner fungicides all improved disease control and yield; two applications of half-rate epoxiconazole with half-rate azoxystrobin or cyprodinil performed best overall. With the range of pathogen sensitivities found in the present study, a DMI such as epoxiconazole remains a useful component of a control programme for R. secalis, but should be supplemented by a partner fungicide with a different mode of action such as a strobilurin or anilinopyrimidine.

Rhynchosporium secalis causes an economically important foliar disease of barley, rye, and other grasses known as leaf blotch or scald. This species has been difficult to classify due to a paucity of morphological features; the genus Rhynchosporium produces conidia from vegetative hyphae directly, without conidiophores or other structures. Furthermore, no teleomorph has been associated with R. secalis, so essentially nothing is known about its phylogenetic relationships. To identify other fungi that might be related to R. secalis, the 18S ribosomal RNA gene and the internal transcribed spacer (ITS) region (ITS1, 5.8S rRNA gene, and ITS2) were sequenced and compared to those in databases. Among 31 18S sequences downloaded from GenBank, the closest relatives to R. secalis were two species of Graphium (hyphomycetes) and two other accessions that were not identified to genus or species. Therefore, 18S sequences were not useful for elucidating the phylogenetic relationships of R. secalis. However, analyses of 76 ITS sequences revealed very close relationships among R. secalis and species of the discomycete genera Tapesia and Pyrenopeziza, as well as several anamorphic fungi including soybean and Adzuki-bean isolates of Phialophora gregata. These species all clustered together with 100% bootstrap support. On the basis of these results, the teleomorph of R. secalis, if it exists, most likely will be a small apothecium produced directly on dead, infected host tissue. The ITS analysis also indicated that higher-level classifications within the discomycetes need to be revised, and that Tapesia and Pyrenopeziza probably do not belong in the Dermateaceae.

The fungicide propiconazole, applied as a foliar spray to swards of perennial ryegrass (Lolium perenne) at four sites in England from 1990 to 1992, reduced the incidence of powdery mildew (Blumeria graminis), Drechslera leaf spot (Drechslera spp.) and Rhynchosporium leaf blotch (Rhynchosporium spp.), increased the number of leaves per tiller and reduced the proportion of dead leaves. Propiconazole increased yield, by 6–7%, at harvests in mid-May, but had no effect at harvests in late June, when the cut herbage was dried to produce hay, although in one hay crop, in vitro organic matter digestibility was increased from 575.6 to 588.5 g kg−1 (P < 0.05). Further research is required to determine the rationale and optimum timing of fungicide application to grassland.

Laboratory tests on 2000 isolates of Rhynchosporium secalis from throughout the UK over a 4-year period revealed a decline in sensitivity to triadimenol and propiconazole but not to prochloraz. Change occurred throughout the UK irrespective of disease pressure, and was not correlated with fungicide use. Resistant isolates were no less pathogenic than sensitive ones. Selection with triadimenol generated a bimodal population distribution, whereas propiconazole produced a gradual shift of unimodal population towards a less sensitive mean. Some cross-resistance occurred between triadimenol, propiconazole and a third triazole, tebuconazole, although the change in sensitivity to tebuconazole was always less than to the other two triazoles. No cross-resistance was observed to the imidazole demethylation inhibitor (DMI), prochloraz. Field-trial data collected over several years showed that the performance of triadimenol, and to a lesser extent, of propiconazole, had declined. Control of Rhynchosporium with these fungicides could be improved by using mixtures with carbendazim. Tebuconazole, either alone or in mixtures with carbendazim or tridemorph, provided the best disease control, and did not appear to select for lower sensitivity. The findings emphasize that certain DMI fungicides may still be used in strategies where performance of other DMIs has been altered because of resistance.

The incidence and severity of infection by fungal diseases was recorded on youngest fully expanded leaves of perennial ryegrass (Lolium perenne) in May and/or September from 1985 to 1987 at 16 sites in England and Wales. Leaves were collected from swards of a single cultivar, Melle, given the same management at each site. Drechslera spp. were present at all sites, and infection exceeded 10% of leaves at eight sites. Rhynchosporium spp. were present at 15 sites but infection exceeded 10% of leaves at only two sites in southern England. Powdery mildew (Erysiphe graminis) was present at 10 sites and infection exceeded 20% of leaves at four sites. Crown rust (Puccinia coronata) was present at six sites, mainly in central and southern England, and infection exceeded 10% of leaves at two sites. Mildew and rust were present only in September, Drechslera was more frequent in September than May and Rhynchosporium was about equally frequent in May and September. The area of leaf damaged by Rhynchosporium ranged from 5 to 23% overall; the range for the other diseases was 1–3%.

Monographella albescens (Thum.) comb.nov., the perfect state of Rhynchosporium oryzae Hashioka & Yokogi ( = Gerlachia oryzae (Hashioka & Yokogi) W. Gams), the rice-leaf scald fungus, is described and illustrated. The taxonomy of both the perfect and imperfect state is discussed. Scanning electron microscopy confirms that the conidiogenous cells are annellidic. Optimum temperature for perithecial production was 26° and the addition of fresh rice leaves to the culture media was a requirement for perithecial production. The fungus is homothallic.

The rice leaf scald fungus, Rhynchosporium oryzae , produces sickle shaped to oblong apedicellate, hyaline conidia measuring 6–15 μm × 3–4.5 μm. They are bicellular and rarely 2-septate. Twelve strains isolated from the Ivory coast and Sierra Leone were studied and placed into four groups based on morphology on polished rice agar. Cardinal temperatures of these isolates were o, 24, 28 and 36 °C. The effect of various media and light on morphology was studied. Optimum concentration of glucose and peptone on dry weight was 1% and for sporulation on solid media was 1% peptone and 0.25% glucose. The fungus was found to be very variable in culture, especially with frequent subculturing.

The subcuticular phase in the development of Rhynchosporium leaf blotch of barley was studied by scanning and transmission electron microscopy. After direct penetration of the cuticle, hyphae grow beneath the cuticle in the region which is rich in pectic substances, often growing along the line where adjacent epidermal cells meet. The cuticle over the hyphae is stretched but not ruptured and there is only localized disruption of the cell wall. Appositions of cell wall material occur on the inner surface of the epidermal cell wall. Close to subcuticular hyphae, short lengths of the plasmalemma of epidermal cells may be separated from the cell wall. The epidermal cells collapse and, in the underlying mesophyll cells, the chloroplasts show degenerative changes.

Spores of Rhynchosporium secalis (Oudem.) J. J. Davis produced a self-inhibitor of germination, the effectiveness of which was increased by increasing concentration, and decreased by the increasing availability to the spores of exogenous nutrients. Barley leaves provided a source of exogenous nutrients irrespective of their susceptibility to Rhynchosporium (leaf blotch).

Germination of Rhynchosporium oryzae was best from 10- to 15-day-old cultures and at pH 6.8 or in rice leaf exudate. The presence of an inhibitor to germination associated with conidia was suggested by the lower germination of unwashed conidia or conidia at higher concentrations.