No description available.

This study considered a novel approach to selecting isolates of Hyphomycete fungi as mycoinsecticides for biological control of aphids in arable crops in the UK. The approach was designed to select isolates which were compatible with both the biotic and abiotic environment. Aphis fabae was chosen as a representative target aphid for bioassays, based on results of preliminary experiments. Eighteen isolates of fungi were screened at a single concentration of 1x 10⁸ conidia ml⁻¹ against apterous adult A. fabae, which were incubated at 23°C. Spray applications were made using an electrostatic rotary atomiser in both laboratory and field experiments. Isolates that originated from aphid hosts were most pathogenic to A. fabae. Four isolates were selected for further studies; ARSEF 2879 (Beauveria bassiana), HRI 1.72 (Verticillium lecanii), Mycotrol strain GHA (B. bassiana) and Z11 (Paecilomyces fumosoroseus). Isolate HRI 1.72 was most virulent to A. fabae in dose-response assays compared to other isolates; at concentrations of 1x 105 conidia ml⁻¹ and above, mortality of aphids due to infection by HRI 1.72 was 100%. Isolates of P. fumosoroseus and V. lecanii were able to grow and germinate better in vitro at low temperatures (10 & 15°C), than isolates of B. bassiana and Metarhizium anisopliae. Aphis fabae and Myzus persicae, inoculated with isolate HRI 1.72 and incubated at 10°C, succumbed to infection after a significantly shorter period of time compared to other isolates. Rhopalosiphum padi was most resistant to infection by the four isolates compared to five other species of aphid. Aphis fabae, Acyrthosiphon pisum, Sitobion avenae, Metopolophium dirhodum, R. padi and M. persicae were most susceptible to infection by isolate HRI 1.72. Aphids infected with isolates of V. lecanii often had fungal sporulation on their legs and died attached to leaves on which they were feeding. The isolates Mycotrol strain GHA and ARSEF 2879 were pathogenic to the 7-spot ladybird Coccinella septempunctata and the generalist parasitoid Praon volucre. The isolates HRI 1.72 and Z11 had very little impact on these natural enemies tested. When aphids of A. fabae were co-inoculated with isolates of Hyphomycete fungi and Erynia neoaphidis, most individuals succumbed to infection with E. neoaphidis. A significant number of aphids died within 24 hours of inoculation and showed no signs of external sporulation. The potential interactions between these natural enemies in the biocontrol of aphids are discussed. The spatial and temporal distribution of aphids and their natural enemies, in field bean and wheat crops, was determined in two field seasons (1997 & 1998). Aphids sampled from the field, after application of Hyphomycete fungi in 1998, mostly succumbed to infection with E. neoaphidis. Epizootics of E. neoaphidis were recorded in both years. Greater numbers of healthy laboratory aphids succumbed to infection with Hyphomycete fungi when they were bioassayed on leaves sampled immediately following spraying (51 - 100%) compared to 24 hours later (8 - 65%). Microclimate recordings showed humidity in both crops was generally >90% overnight and differences were as great as 15% between the top and bottom of crop canopies. Temperature differences were as great as 5-7°C between individual sensors. The implications of using a biorational approach as part of the development of Hyphomycete fungi as mycoinsecticides for the control of aphids is discussed.

The aim of this work was to assay the effects of previous history of organic amendment to soils in the field on the ability of those soils to mineralise mustard, a non-legume green manure. Soil and 15N labelled mustard mineralisation was followed in laboratory microcosms. Volatilised N was assayed by direct acid trapping of N in glass fibre disks, followed by direct combustion isotope ratio mass spectrometry. Animal manures, green manures and straw added to the soil in the field in the previous season, same season and for 7 years continuously did not significantly affect these soils' ability to mineralise mustard in microcosms. Nitrification and mineralisation were the dominant processes during the first 12 days of incubation. Volatilisation rates were 1000-fold lower than mineralisation or nitrification rates. Mustard N accounted for between 1-3% of the soil mineral N, whereas only a maximum of 0.01% of mustard N was volatilised over 24 days. Soils sampled at different times in the season decomposed mustard at similar rates at stimulated low spring temperatures. Nitrification rate was reduced 5-fold more than the mineralisation rate at 8oC. Straw incorporation for seven years did not affect the subsequent recovery of 15N enriched fertiliser or of 15N from labelled straw, by oil seed rape. 15N labelled fertiliser contributed up to 63% of the winter barley N. The labelled barley straw subsequently contributed 16% of the oil seed rape N in the absence of any applied fertiliser. Ploughing in straw in the autumn, in the absence of applied fertiliser had no yield penalty or effect on crop uptake, and may retain more mineral N in the upper soil layers, lessening the risk of leaching over the winter period. The results obtained here emphasise the importance of additions of organic materials to soil in supplying plant nutrients and minimising nutrient losses.

No description available.

This study was part of a larger research programme designed to obtain a method of improving the feed value of waste straw to ruminants, using a selected microorganism. The work reported here was carried out to assess the potential of Coprinus cinereus (Schaeff ex Fr.) S.F. Gray sensu Konr. for this purpose, to upscale the most promising treatments and to investigate the natural colonisation of straw by the fungus. The breakdown of sterile barley straw was investigated over a range of pHs maintained with ammonia and hydrochloric acid solutions. Hemicellulose and cellulose were found to be attacked, with hemicellulose decomposed preferentially. At optimum growth conditions, in vitro digestibility of the straw was increased to the level of good quality hay, although this declined after peaking. Digestibility increase was correlated with utilisation of hemicellulose and cellulose in the short term. Larger scale biodegradation trials using unsterile straw showed that a consistently upgraded product could be obtained using an inoculum of C. cinereus spores in 1% wjw ammonia solution with loose straw in polythene sacks. The low pro­tein content of the upgraded material indicated that it was unsuitable as a complete ruminant diet. A technique was developed to study the activity of C. cinereus and other fungi in cereal field soil. It was shown that C. cinereus is an active component of the fungus flora of barley field soil, indicating that the propagules of C. cinereus found in harvested straw arise from the soil. The feasibility of linking a straw biodegradation process to an animal slurry treatment system, which serves as an ammonia source was investigated. The economic aspects of such a scheme were discussed.

The antifeedant and insect growth regulatory (KGR) activities of azadirachtin, its natural analogue 3-tigloylazadirachtol and its synthetic analogues 22,23-dihydroazadirachtin and 22-alpha-bromo-22,23-dihydro-23-alpha,beta-ethoxyazadirachtin were investigated using different bioassays on Schistocera gregaria (F.) and Locusta migratoria (R &38 F). The effects of azadirachtin on midgut histology were studied at the light microscopical and electron microscopical level. Light microscopy revealed that azadirachtin affected midgut histology in a dose and time dependent manner. Increasing effects were seen at doses of 5-15 mug g-1 body weight. With a dose of 1 mug g -1, effects were apparent but recovery occurred after three days. Azadirachtin caused the normal elongated midgut epithelial cells to become cuboidal; thickening of the connective tissue with invading regenerative cells. The gut musculature was swollen. Electron microscopy showed the midgut cells to undergo necrosis with swelling of the mitochondria and endoplasmic reticulum, reduction in glycogen granules and increaesd autophagic vacuoles. Bursting and disruption of the cell contents was sometimes seen. Such effects were not seen in starved insects. Feeding activities, measured in terms of antifeedant indices (AI) and consumption rates (CR) in binary choice bioassays on fifth instar nymphs demonstrated dose-dependent variations for all the compounds in both species of insects. S.gregaria was more discriminatory and more sensitive to azadirachtin and its analogues than was L.migratoria. ED_50's were measured for all compounds tested. Ingestion rates of the compounds showed a dose-dependent decrease with increasing dose. The highest intake of the compounds was observed mostly at an AI of 50-60&'37. The short- and long-term effects of topical application and low doses (0.1 and 1.0 mug g-1 body weight) of azadirachtin, the analogues and an additional unidentified compound X (related to bromeothoxyazadirachtin) were measured in S.gregaria. The effects on growth were reduced body weight and reduced feeding as measured by faecal pellet production. Azadirachtin induced the highest mortality and most deaths occurred within the first few days of treatment; the analogues were less acutely toxic. Mortalities at the moults were also dose related. In all the insects which survived, none of the compounds exerted any significant effects on dry body or ovary weights, egg size or fecundity. Thus once toxic effects were overcome, the insects matured and reproduced normally; none of the compounds had any long term accumulative effects.

The present series of experiments were carried out to determine the effect of i) ensiling straw and grass in various proportions, on chemical composition and nutritive value of silage, ii) homogeneity of mixing of grass and straw on fermentation quality and nutritive value of silage, iii) urea and/or enzyme treatment of straw on chemical composition and nutritive value of grass+ straw silage, and iv) co-conservation of grass-straw on nutritive value of straw. In some experiments feeding value is assessed in the laboratory, and in others by actual feeding trial. In addition a method was developed for determining water in silages using near infrared transmittance spectroscopy. Mixing straw with grass during ensiling diluted crude protein but increased the cell wall constituents. Straw modified fermentation, and more lactic acid and acetic acid were produced in grass+ straw silage than grass-only silage. The fermentation was also affected by the type of grass. The concentrations of ammonia were higher and lactic acid and acetic acid were lower in the silages made from grass/legume than that from only grass. A thorough mixing of grass+ straw is required because ensiling grass and straw in alternate layers increased butyric acid content in silage. Animals ate 22% less dry matter from the silage made in layers than from that made from thoroughly mixed grass+ straw. However, more intensive mixing of grass and silage was not beneficial, as it reduced the digestibility of nutrients and only slightly increased dry matter intake. Increasing the proportion of straw in grass+ straw in a grass+ straw silage reduced intakes of dry matter and digestibility of nutrients. Treatment of straw with urea (60 g/kg straw DM) increased lactic acid content and reduced the contents of cell wall constituents. Urea increased intake and digestibility of nutrients, but enzyme had small effect on intake and digestibility of nutrients by sheep. However, a combination of urea and enzyme was most effective, and increases in the intake of dry matter and digestibility of nutrients were significantly greater in these silages than those treated with either urea or enzyme. The straw composition of cell wall constitutents from straw occurred during ensiling. A method developed for determination of water using NITS is fast and reliable. The model uses the absorbance ratio (OD at 1940 nm/OD at 2284 nm) as a predictor of water in dimethyl sulphoxide which was used to extract water from silages.

Chlormequat can be applied to winter barley for growth manipulation with a view to increasing ear number per m<SUP>2</SUP> and hence grain yield, but, reviewing the literature on field trials showed the effects were not consistent. Previous work showed that the grain yield per m<SUP>2</SUP> of winter barley was strongly correlated with the number of grains per m<SUP>2</SUP> which itself was shown to be mostly influenced by the number of ears per m<SUP>2</SUP>. Three agronomic factors, cultivar, sowing date and nitrogen fertiliser, were identified from the literature as important influences on ear production in winter barley. These were therefore considered to have the potential to modify plant response to chlormequat, in terms of ear production, and might thus account for some of the inconsistency of the effect of chlormequat on grain yield in field trials. The intention of these studies was to move towards a description of winter barley production systems into which chlormequat may be integrated to consistently increase grain yield. Because little information was available on the growth, development and grain yield components of field grown modern winter barley cultivars, these attributes were monitored and analysed in detail for a range of modern cultivars grown at two sites in north-east Scotland in the harvest years 1984 and 1985. Tipper and Maris Otter were identified as strongly contrasting cultivars, being good examples of the extremes of the range of growth parameters found. In addition, the analyses identified the extreme importance of high cultivar biomass per plant for the attainment of high cultivar grain yield per plant. Evidence that increases in biomass have already contributed to the higher grain yields of modern cultivars of both spring barley and winter wheat was also found within the literature. The effect of chlormequat at a range of application times in the spring on early and late sowings of Igri, Tipper (low ear production) and Maris Otter (high ear production) was tested. When averaged over all cultivars and sowing dates chlormequat applied prior to stem extension significantly increased the number of ears per m<SUP>2</SUP> in 1983--4 which led to increases in grain yield. In 1984--5 chlormequat applied at the start of stem extension significantly increased the number of grains per ear and significantly increased grain yield; within-plant uniformity, in terms of shoot contribution to grain yield, was also increased. Chlormequat had no consistent effect on the grain yield of the cultivars Igri and Tipper, but did increase the grain yield of both early and late sown Maris Otter by increasing the number of grains per m<SUP>2</SUP>. These higher grain numbers were achieved through consistent increases in the number of ears per m<SUP>2</SUP> which were nearly always associated with increases in the number of grains per ear on the main stem and early primary tillers. These larger sink sizes of Maris Otter followed temporary reductions in shoot height which were offset by compensatory increases in shoot growth. The growth, development and grain yield components of Maris Otter were described in detail with a view to enabling cultivars with similar growth characteristics to be identified. Application of nitrogen fertiliser did not modify the effect of chlormequat on shoot height or shoot dry weight. In these experiments chlormequat increased neither ear number per m<SUP>2</SUP> nor grain number per ear; therefore, the effect of nitrogen application strategy on the ability of chlormequat to increase in sink size could not be evaluated. It was suggested that application of chlormequat to Igri winter barley receiving more than 100 kg N/ha is unlikely to reduce grain yield. These investigations confirmed the extreme importance of high crop biomass for the attainment of high grain yield. The findings of these investigations together with the findings of a re-analysis of advisory service field trial data on the effect of chlormequat on winter barley are discussed in relation to commercial winter barley production. Finally, it is suggested that more consistent increases in grain yield may be achieved by restricting the use of chlormequat for tiller manipulation to cultivars of the Maris Otter type such as Halcyon and Pipkin which are slow developing, produce relatively large numbers of tillers and eventually many ears per plant.

The nutritional value of molassed sugar beet feed as a dietary component was assessed in a series of three experiments. In experiment 1, the effect of molassed sugar beet feed pellets (32 or 64 g/kg fresh weight silage) either ensiled or fed separately with big-bale silage on silage quality and performance of male castrate sheep (initial liveweight 29 kg) was studied. On average, the inclusion of molassed sugar beet feed increased silage dry matter, water soluble carbohydrate and lactic acid concentrations and decreased silage ammonia concentrations. Molassed sugar beet feed either ensiled or given as a supplement, significantly improved total dry matter intakes and liveweight gain (P< 0.05) and metabolisable energy intakes (P< 0.01) in lambs. Experiment 2 was carried out to investigate the effects of feeding two levels of fishmeal in addition to molassed sugar beet feed as supplements to big-bale grass silage fed ad libitum to beef steers of 290 kg initial liveweight. Bale silage was given alone or supplemented with 800 g molassed sugar beet feed/day, molassed sugar beet feed + 125 g fish meal/day or molassed sugar beet feed + 250 g fish meal/day. Supplementation of big-bale silage with molassed sugar beet feed did not increase total dry matter intake or improve liveweight gain. Adding FM to a diet composed of big-bale silage and molassed sugar beet feed significantly increased liveweight gain, total ruminal volatile fatty acid and ammonia concentrations. The effect of diets differing in the ratio of molassed sugar beet feed to barley and the inclusion of yeast culture on growth and rumen metabolism of sheep (initial liveweight 36 kg) was examined in experiment 3. Four diets, which were offered ad libitum , consisted of pelleted or molassed sugar beet feed, barley and soya-bean meal in the following proportions (DM basis) either A, 770:170:60 or B, 470:470:60. Diets A and B were fed with and without 2 g Yea-Sacc/head/day.

Low input grassland systems depend on cheap fertiliser sources, such as clover or animal manures, to maintain sward productivity. Clover is a poor competitor for phosphate (P2O5) and potash (K2O), a mixed sward will therefore require adequate inputs of these nutrients. Nitrogen (N) leads to the suppression of clover. Recycling of cattle slurry would be followed by small N and P2O5 but large K2O effects. The K2O and P2O5 would be expected to have a beneficial effect on the clover while the N would be detrimental. Two investigations into the balance between these aspects of cattle slurry on clover in a mixed sward were performed. Slurry N led to clover suppression, this effect was strongest following spring applications. K2O had a beneficial effect on the clover, the P2O5 supplied had a small positive effect but was insufficient to fully meet the clover's requirements. There was a suggestion that these beneficial effects were strongest following summer applications. In addition to these fertiliser effects, non nutritional secondary effects often followed slurry with a deleterious action on the clover. These effects were most common following higher rates of slurry and summer applications. A further investigation was performed to establish the effect of varying clover variety and companion grass species on the clover's susceptibility to cattle slurry N and secondary effects and the nature of these effects following pig slurry applications. This revealed that clover's susceptibility to slurry N was inversely related to leaf size. No difference in secondary effects susceptibility arose with different clover varieties or companion grass species. Pig slurry was not accompanied by secondary effects. Slurry applications to mixed swards may therefore have positive and negative nutritional effects on the clover component but non nutritional secondary effects may also act with a deleterious effect on the clover.