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Summary • Winter wheat (Triticum aestivum) and winter barley (Hordeum vulgare) were grown on soil contaminated with different levels of a marked bacterial potato pathogen Erwinia carotovora ssp. atroseptica (Eca) from a previous blackleg-infected potato crop, to determine whether the presence of this pathogen could affect disease development on wheat and barley. • The diseases ‘septoria leaf blotch’ and ‘powdery mildew’ on wheat (caused by Septoria tritici and Blumeria graminis f. sp. tritici, respectively) and ‘scald’ or ‘rhynchosporium’ on barley (caused by Rhynchosporium secalis) were assessed over two growing seasons, and the presence of the marked Eca strain monitored. • Wheat diseases were greater on the areas with high levels of Eca contamination than on areas with low-level contamination. Rhynchosporium on barley was not affected overall, although it decreased on the high-level contamination areas early in the season. The Eca strain was detected on the upper foliage of both wheat and barley. • Increased S. tritici symptoms in the field may be due to ‘synergistic’ interactions between the Eca and the fungal mycelium, as reported in previously published laboratory experiments. The potential importance of such fungal–bacterial interactions is discussed.

The article is devoted to the effect of biofertilizers (Bioklad and Vermix) on the severity of common diseases of spring barley in field trials conducted in the Orel region. The authors estimate risks of spring barley diseases and analyse the results of the three-year experiment, carried out under certain weather and climate conditions. The subject of the research is the spring barley crop Suzdalets under intensive farming (zoned for 2, 3, 5 regions of Russia). For a more comprehensive assessment, the experimental process includes separate and combined application of biofertilizers at two different doses. The results of the experiment shows that spring barley crops have responded to all tested combinations of treatment and, at the same time, biofertilizers Bioklad and Vermix, regardless of the doses of application used, had a positive treatment effect and reduced development of severe plant diseases such as root rot by 8.4%, Helminthosporium spot by 29.2%, powdery mildew by 28.9%, Rhynchosporium by 26.3%, stem rust by 65.9%, Septoria spot by 24.4%, and Fusarium head blight by 12%. The most productive agrocenosis of spring barley was formed with the use of Bioklad: barley yield was 0.59 t/ha at a dose of 1 L/ ha and 0.61 t/ha at a dose of 2 L/ha.

The disease pressure from Pyrenophora teres, Rhynchosporium graminicola, and Ramularia collo– cygni varies widely between years and locations, which highlights the need for using risk models to avoid unnecessary use of fungicides. Three disease risk models were tested in thirty– three field trials during two seasons in five countries in order to validate and identify situations favourable for barley leaf blotch diseases in the Nordic–Baltic region. The tested models were: The Crop Protection Online (CPO), which uses number of days with precipitation (>1 mm), cultivar resistance and disease data as basis for risk assessments; the humidity model (HM) which signals a risk warning after 20 continuous hours with high humidity, and the Finnish net blotch model (WisuEnnuste), which calculates a risk based on previous crop, tillage method, cultivar resistance and weather parameters. The risk models mostly gave acceptable control of diseases and yield responses compared with untreated and reference treatments. In the dry season of 2018, the models recommended 88–96% fewer applications than the reference treatments, while in 2019, the number of applications was reduced by 0–76% compared to reference treatments. Based on yield increases, the recommendations were correct in 50–69% of the trials compared to one–treatment references and 69–80% of the trials when references used mainly two treatments.

Modern cereal cultivars are highly adapted to, and normally bred and trialled under, high input, high soil disturbance conditions. On-farm conditions are often suboptimal for high yield and frequently use minimal soil tillage, sometimes no-tillage, and therefore, cultivars may be differentially adapted to such conditions. We report a series of trials across 10 years comparing multiple cultivars within years and smaller numbers across years to identify stable cultivars showing preferential adaptation to different levels of soil tillage. Cultivars responded differentially to inversion and non-inversion tillage but were not affected by the level of cultivation within each of these tillage types. Yield declined over time but much more so in the non-inversion tillage treatment. Rhynchosporium symptoms were also increasingly suppressed in the non-inversion tillage type. Several cultivars were identified that showed strong adaptation to tillage type, and some of these were consistent across several trial years. These cultivars can be used to identify traits and genotypes associated with tillage adaptation to target breeding for on-farm conditions.

Fungal plant diseases driven by weather factors are common in European wheat and barley crops. Among these, septoria tritici blotch (Zymoseptoria tritici), tan spot (Pyrenophora tritici-repentis), and stagonospora nodorum blotch (Parastagonospora nodorum) are common in the Nordic-Baltic region at variable incidence and severity both in spring and winter wheat fields. In spring barley, net blotch (Pyrenophora teres), scald (Rhynchosporium graminicola, syn. Rhynchosporium commune) and ramularia leaf spot (Ramularia collo-cygni) are common yield limiting foliar diseases. We analysed data from 449 field trials from 2007 to 2017 in wheat and barley crops in the Nordic-Baltic region and explored the differences in severity of leaf blotch diseases between countries and years, and the impact of the diseases on yield. In the experiments, septoria tritici blotch dominated in winter wheat in Denmark and southern Sweden; while in Lithuania, both septoria tritici blotch and tan spot were common. In spring wheat, stagonospora nodorum blotch dominated in Norway and tan spot in Finland. Net blotch and ramularia leaf blotch were the most severe barley diseases over large areas, while scald occurred more locally and had less yield impact in all countries. Leaf blotch diseases, with severity >50% at DC 73–77, caused an average yield loss of 1072 kg/ha in winter wheat and 1114 kg/ha in spring barley across all countries over 5 years. These data verify a large regional and yearly variation in disease severity, distribution and impact on yield, emphasizing the need to adapt fungicide applications to the actual need based on locally adapted risk assessment systems.

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.

The National Centre for Plant Genetic Resources (NCPGRU) formed a genetic collection of spring barley comprising 315 accessions from 25 countries with identified genes of resistance to major diseases, which is of practical value for breeding. The aim and tasks of the study was to analyze literature, to estimate the new gene pool of spring barley, to systematize and select accessions, to form a genetic collection by resistance to disease. Materials and methods. The study material was spring barley collection accessions. The genetic collection of spring barley includes 114 reference accessions. Results and discussion . Multi-year field studies revealed highly resistance to powdery mildew in accessions carrying genes Ml-a3; Ml-g; Ml-a13; Ml-a12 (Reg1t12) reg 6e; Ml- (la), Ml-a7; Ml-k; Reg 1g7; Reg 4ac; Reg 2ac . 7-9 point resistance to dwarf rust was determined by genes Rph12 and Rph3. Genes Un2; Run3; Un-3, Un4, Un5, Un6, rh6, and rh7 were effective against loose smut in our environment. Resistance to rhynchosporium leaf scald was observed in accessions with genes Rh4; Rh-1 . Conclusions. As a result of multi-year studies, the genetic collection by resistance to diseases, which comprises 315 accessions with 113 expression levels carrying 86 gene groups, was formed. It can substantially cover breeding needs for developing modern spring barley varieties that would be resistant to powdery mildew, dwarf rust, loose smut and rhynchosporium leaf scald. Among accessions, we also found sources of valuable traits, in particular, of high 1000-grain weight (Maris Concord – 49.1 g; Harry – 49.3 g; Medina – 49.0 g; Delita – 49.8 g; and Quantum Plus - 50.3 g) and of high yield capacity (Regatta - 780 g/m 2 ; Tennis - 900 g/m 2 ; Keti - 790 g/m 2 ; Jarek - 815 g/m 2 ; and Femina - 820 g/m 2 ). Use of collection accessions with identified genes will improve the breeding efficiency and accelerate breeding under the conditions of the Forest-Steppe of Ukraine

Cultivars and some cultivar mixtures of spring barley were grown under inversion and non-inversion tillage conditions for three or four years and assessed for disease and yield in order to obtain genotypes that can be used to determine the mechanisms of cultivation adaptation. In general, the higher-yielding cultivars under inversion tillage conditions gave lower yields under non-inversion tillage, whereas low-yielding older cultivars showed relatively smaller reductions in yield under non-inversion tillage. A few cultivars showed preferential yield performance for either inversion or non-inversion tillage and this was irrespective of their overall yield performance. There was no pedigree or breeding programme link between these cultivars and no above-ground gross morphological trait observed was associated with tillage adaptation. Root hairs may contribute to inversion tillage adaptation as a root hair absence mutant was associated with non-inversion adaptation and it is likely that other root-associated traits are responsible also for tillage adaptation. There was no overall cultivar or tillage interaction with rhynchosporium symptoms but a differential tillage interaction may occur in individual years. We have identified clearly contrasting cultivars and tested their across-season robustness with respect to tillage treatment for further detailed mechanistic studies and identification of tillage adaptation traits.

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.

Leaf blotch is a globally important disease of barley crops and other grasses that is caused by at least five host-specialized species in the fungal genus Rhynchosporium. The pathogen R. commune (specialized to barley, brome-grass and Italian ryegrass) has long been considered to reproduce only by asexual means, but there has been accumulating evidence for recombination and gene flow from population genetic studies and the detection of complementary MAT1-1 and MAT1-2 isolates in a c. 1:1 ratio in the field. Here, it is demonstrated that 28 isolates of the closely related species R. agropyri (on couch-grass) and R. secalis (on rye and triticale), collected from Europe, were also either of MAT1-1 or MAT1-2 genotype and that the distribution of mating types did not deviate significantly from a 1:1 ratio. Evidence is then provided for MAT1-1-1 and MAT1-2-1 gene expression during mycelial growth for all three species. By contrast, 27 isolates of the more distantly related R. orthosporum (on cocksfoot) and R. lolii (on Italian and perennial ryegrasses) from Europe were exclusively of the MAT1-1 genotype, and expression of the MAT1-1-1 gene could not be detected during mycelial growth. These data suggest that cryptic sexual cycles are more likely to exist for R. commune, R. agropyri and R. secalis than for either R. orthosporum or R. lolii. A phylogenetic analysis of partial MAT1-1 idiomorph sequences resolved these five species into two distinct groups (R. commune, R. agropyri and R. secalis versus R. orthosporum and R. lolii) but provided only limited resolution within each group.

Plectosporium alismatis is a fungal pathogen that is being investigated as a biocontrol agent for suppressing starfruit (Damasonium minus), a significant weed of Australian rice fields. The aim of this research was to study the effect of the fungus on weed competition and its interactions with chemical herbicides. Conidial germination was significantly reduced by Londax® (bensulfuron-methyl), while MCPA had no effects. Glasshouse trials showed evidence of synergism between the fungus and 1.56% of the recommended dose of Londax®, in reducing the weed growth. The application of inoculum (conidia suspended in water) in the glasshouse eliminated weed competition with rice. In the field, the reduction in weed growth caused by the fungus did not significantly eliminate starfruit competition with rice. This is thought to be due to the presence of other weeds.

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.

An outline is given of results for the transfer of new resistances against leaf rust and barley mosaic viruses from Hordeum bulbosum into winter barley. Progenies from backcrosses of barley cultivars with H. bulbosum hybrids were tested both in conventional breeding trials and in additional tests under controlled conditions. Resistance to both pathogens proved to be stable and of good heritability, with differences occurring which depended on the combinations used. Lines with resistance to all leaf rust and mosaic viruses tested, or to either one, were selected. Both resistances segregated independently.

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.

Summary Samples from 200–400 randomly selected winter barley crops were taken annually at growth stage 71–73 from 1981 to 1991, with the exception of 1984 and 1985. The number of samples from each region was proportional to the area of barley growth in each region. The percentage of the area of the top two leaves affected by diseases and the severity of stem base diseases were recorded. Mildew (Erysiphe graminis) was the most widespread of the foliar diseases and in three years (1982, 1986 and 1991) was also the most severe. Rhynchosporium (Rhynchosporium secalis), net blotch (Pyrenophora teres) and brown rust (Puc-cinia hordei) were also prevalent in some years. Of the stem base diseases, fusarium was often the most widespread. Eyespot (Pseudocercosporella her-potrichoides) severity varied widely from year to year ranging from 1.2% of stems affected by moderate or severe symptoms in 1982 to 24.1% in 1988. There were regional differences in the severity of mildew, rhynchosporium, brown rust, halo spot (Selenophoma donacis) and eyespot. Cultivar resistance affected disease severity and previous cropping affected eyespot and less frequently mildew, rhynchosporium and net blotch. Eyespot, and to a lesser extent, sharp eyespot, were less severe in late- than in early-sown crops. The percentage of crops treated with a fungicidal spray increased from 72% in 1981 to 95% in 1991. The use of benzimidazole fungicides for the control of eyespot declined in response to the development of resistance, and more recently the use of prochlo-raz also declined. Broad spectrum DMI fungicides were widely used, and the use of morpholines to improve mildew control increased significantly. The proportion of crops grown from seed treated with a non-mercurial fungicidal seed dressing reached a peak of 47% in 1986 but subsequently declined to 22% in 1990 and 1991.

Summary Samples from 200–300 randomly selected spring barley crops were taken annually at growth stage 73–77 (milky ripe) from 1976 to 1980. The number of samples from each region was proportional to the area of barley grown in each region. The percentage of the area of the top two leaves affected by diseases was recorded. Mildew (Erysiphe graminis) was the most widespread and severe disease recorded. Brown rust (Puccinia hordei) and rhynchosporium (Rhyn-chosporium secalis) occurred frequently but at relatively low levels. Yellow rust {Puccinia striiformis) and septoria (Septoria nodorum) were seen on less than 50% of the samples in most years, and halo spot (Selenophoma donacis) and net blotch (Pyrenophora teres) were rarely recorded. There was an association between the severity of rhynchosporium and the number of rain days in May and June. The highest levels of brown rust occurred in the south and east and rhynchosporium was more common in Wales and the south-west than in the east, but there were no differences in the regional distribution of other diseases. Cultivar resistance, sowing date, previous cropping and fungicide usage were all found to be associated with altered disease levels. The proportion of crops treated with a foliar fungicidal spray rose from 26% in 1976 to 47% in 1980. The use of tridemorph declined but that of triadimefon increased reaching 29% of crops treated by 1980. The use of ethirimol as a seed treatment declined from 16% of crops grown from treated seed in 1976 to 7% in 1980. Estimated yield losses between 1976 and 1980 varied between 4% and 9% due to mildew, between 0.3% and 0.8% due to brown rust and between 0.2% and 0.5% due to rhynchosporium.

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%.

Rhynchosporium secalis is one of the most destructive pathogens of barley worldwide, causing yield decreases of up to 40% and reduced grain quality. Rhynchosporium is a polycyclic disease. Primary inoculum includes conidia produced on crop debris, infected seeds and possibly ascospores, although these have not yet been identified. Secondary disease spread is primarily by splash dispersal of conidia produced on infected leaves, which may be symptomless early in the growing season. Host resistance to R. secalis is mediated by both 'major' or host-specific genes (complete resistance) and 'minor' genes of smaller, generally additive effects (partial resistance). Crop growth stage and plant or canopy architecture can modify the expression of resistance. Resistance genes are distributed unevenly across the barley genome, with most being clustered on the short arms of chromosomes 1H, 3H, 6H and 7H, or in the centromeric region or on the long arm of chromosome 3H. Strategies used to manage rhynchosporium epidemics include cultivar resistance and fungicides, and also cultural practices such as crop rotation, cultivar mixtures and manipulation of sowing date, sowing rate or fertiliser rate. However, the high genetic variability of R. secalis can result in rapid adaptation of pathogen populations to render some of these control strategies ineffective when they are used alone. Sustainable control of rhynchosporium needs to integrate major-gene-mediated resistance, partial resistance and other strategies such as customized fungicide programmes, species or cultivar rotation, resistance gene deployment, clean seed and cultivar mixtures.

The inundative application of conidia of the plant pathogenic fungus, Rhynchosporium alismatis, to seedlings of Sagittaria pygmaea, S. guyanensis, and Alisma canaliculatum resulted in seedling death or significant growth suppression. In quarantine pot trials, inoculation of S. guyanensis seedlings caused reductions in average plant height of 60% and reduced leaf and root dry weights, by 89 and 84%, respectively. There was also high seedling mortality. Smaller, though significant, reductions in various growth parameters occurred in the other species when similarly inoculated. Alisma canaliculatum, Echinodorus rostratus, S. brevirostra, S. guyanensis, and S. pygmaea are recorded as new hosts of the fungus. The data indicate the potential use of this fungus as a mycoherbicide in temperate rice crops. Research is continuing on virulence and formulation to improve mycoherbicide efficacy.

Leaf diseases caused by Mastigosporium rubicosum (cause of eyespot), Rhynchosporium orthosporum (cause of scald), and Cercosporidium graminis (cause of leaf streak) were identified on orchardgrass (Dactylis glomerata) grown for seed. Fungicides (captafol, chlorothalonil, and propiconazole) were applied up to three times per year to plants in different stages of growth for 5 yr (1984-1988). Leaf area damaged by diseases (primarily scald) ranged from moderate to severe depending on the yearly variation in precipitation

Slight infection by Drechslera siccans or Rhynchosporium spp. significantly reduced in vitro dry matter digestibility, water-soluble carbohydrate and the total amino acid content of Italian ryegrass (Lolium multiflorum) foliage. The concentration of all 15 amino acids detected was reduced, with arginine reduced significantly more than the others. Total nitrogen was either increased or not changed, and the amino acid composition was not altered. Limited work with Drechslera festucae on tall fescue (Festuca arundinacea) gave similar results. Small samples of healthy and diseased grass leaves at three different physiological stages were used to detect these changes. Limited leaf spotting by D. siccans caused metabolic changes of the same magnitude as extensive leaf blotching by Rhynchosporium. Impaired photosynthesis and growth of the fungi within the leaf tissues are possible causes of these changes. Decreased digestibility and increased dry matter content of diseased grass foliage could be of great practical importance.

Surveys of perennial and Italian ryegrass swards (Lolium perenne L. and L. multiflorum Lam.) at regular intervals in 1977 and 1978 in Berkshire, Wales and Devon confirmed that leaf infection by Drechslera spp. was the most frequently occurring foliar fungal disease. Rhynchosporium spp. and Puccinia coronata Corda were also recorded but in contrast to Drechslera spp., which caused damage throughout the year, attacks by these two fungi were only sporadic. The incidence of Drechslera was greater in 1977 than in 1978 and was greater in Berkshire where most fields were infected in both years than in Wales and Devon. Both perennial and Italian ryegrasses were infected. The number of leaves damaged increased with leaf age. Damage was greater on fields managed for conservation than those which were grazed. Infection increased from February onwards and was greatest in autumn. It is concluded that Drechslera might be controlled by removing infected herbage in autumn by cutting. Rhynchosporium spp. were prevalent only in Berkshire and more Italian ryegrass fields (ca, 50%) were infected than perennial ryegrass fields (ca, 10%). Infection was confined to the period March to May. This pathogen caused more leaf area damage than Drechslera. Puccinia coronata occurred only once in Devon and Wales. In Berkshire incidence was confined to 1978 and was common from September to November, when 60–70% of both Italian and perennial ryegrass fields were infected. Some difference between perennial ryegrass cultivars was observed.

Leaf scald of rice (Rhynchosporium oryzae Hashioka & Yokogi) is reported from Brunei. The influence of cultivation system and fertiliser regime on the severity of the disease is discussed. The presence of adequate nitrogen appears to increase the severity of the disease. Leaf scald has the potential of becoming a serious threat to rice in the area.

In field evaluation trials nine test fungicides significantly reduced the incidence and severity of leaf scald disease of rice caused by Monographella albescens (Thum)(Rhynchosporium oryzae Hashioka & Yokogi) and increased the yield. Of these fungicides Difolatan (captafol) and Dithane M‐45 (mancozeb) were more effective than the other fungicides. Relatively longer persistence of fungicidal residues was detected in three test chemicals, i.e., Blitox‐50 (copper oxychloride), Difolatan and Dithane M‐45. Amount of rainfall appeared to be a main weather factor in influencing persistence of a fungicide.

SUMMARY Rhynchosporium orthosporum was isolated from Lolium multifiorum from breeders’ plots at Aberystwyth twice as often as R. secalis. R. orthosporum from Dactylis glomerata, L. multiflorum or L. perenne would infect only the host genus from which it was isolated. R. secalis from L. multiflorum would produce symptoms not only on L. perenne, but on Hordeum sativum as well. Significantly, this was of race U.K.1, the most common race on H. sativum. Of 20 genotypes of L. multifiorum cv. RvP, 17 ranked similarly for level of resistance to both pathogen species. However, the remaining three genotypes were resistant to one, but markedly susceptible to the other. Progeny of selected resistant genotypes were far more resistant than the original cultivar. This suggests that there are reasonable prospects for resistance breeding.

SummaryExperiments of balanced design in harvest years 1981 and 1982 were used to measure interactions between plots of winter barley with different amounts of leaf blotch, caused by the splash-dispersed pathogen Rhynchosporium secalis. On the appropriate transform scales (logarithms of counts and logits of percentages), the effects of extreme treatments on neighbouring plots were up to 30% of the effects of the same treatments on the plots to which they were applied. Powdery mildew (Erysiphe graminis f.sp. hordei) was commonly least severe in plots with most leaf blotch except soon after fungicide sprays had been applied which, although chosen to decrease leaf blotch, also had short-lived effects on mildew. Consequently, contrasts in mildew between differently treated plots changed sign during the season. The effects of the same treatments on neighbouring plots similarly changed with time but not necessarily in phase with their direct effects. Analyses of the rhynchosporium data that recognized the effects of neighbouring treatments typically had much smaller residual mean squares than analyses that ignored neighbour effects but assumed randomized block designs.Treatments had mostly small effects on grain yield but these data from two of the experiments showed marked positional variation. Individual plots yields from one of these experiments, testing five treatments, are quoted in the appendix so that they are available to others with an interest in alternative methods, such as nearest-neighbour models, to adjust for local correlations between plots.