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Acremonium loliae is an endophytic fungus which infects plants of perennial ryegrass (Lolium perenne), an important pasture grass in New Zealand and much of Western Europe. In New Zealand the endophyte-ryegrass association was found recently to give rise to tremorgenic substances (lolitrem A and B), which are the cause of a serious disorder of grazing and domestic livestock there. The endophyte also confers resistance in ryegrass plants to certain insect pests in New Zealand and enhances plant growth even in the absence of pests. In the present work 61 swards at 52 widespread sites in the U.K. were checked for the presence of endophyte mycelium, and it was found in 14 swards, of which 12 were at least 15 years old. ELISA (enzyme-linked immunosorbent assay) tests confirmed that the fungus was A. loliae. Also, lolitrem B was detected in plants from most of the sites where the mycelium was found; this appears to be the first time this tremorgen has been reported in the U.K. or perhaps in Europe. In a small-plot experiment at two sites with newly sown perennial ryegrass the endophyte appeared to have no effect on infestation by frit fly larvae, a major pest of seedling ryegrass plants. Also, in the present work, the endophyte had no measurable effect on the growth or overwinter mortality of larvae.

Ryegrass swards at fourteeo widely separated sites in England were assessed for yield, botanical composition and invertebrate populations, with and without insecticide treatment during a 4-year period. Treatment with insecticide reduced the numbers of almost all invertebrate groups sampled and increased grass growth at some time at all but one site. Annual DM output was increased by 0-32% depending upon the site concerned. Evidence is presented which suggests that the yield increases were due to the suppression of aphids, plantsucking bugs, stem-boring fly larvae, and perhaps nematodes.

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A comparative study was conducted on earthworm communities in a conventional winter wheat monocropping system and a low-input intercropping system in which successive crops of winter wheat were direct-drilled into a permanent white clover sward. Earthworm abundance, biomass and species composition under the two cropping systems in the second and third years of successive cropping were assessed each spring and autumn in farm-scale field plots at four sites using formalin and electrical extraction methods. The wheatclover cropping system supported larger earthworm communities (overall mean abundance 548 individuals m -2 , 137 g biomass m -2 ) than conventional wheat monocropping (194 individuals m -2 , 36 g biomass m -2 ). Between one and five more earthworm species were recorded in the wheatclover system than in the wheat system at three out of the four study sites. Wheatclover cropping especially favoured species belonging to the epigeic and epigeic/anecic ecological groups such as Lumbricus castaneus, L. festivus, L. rubellus, juvenile Lumbricus and Satchellius mammalis. Earthworm communities in the wheatclover cropping system were comparable in size and species composition to communities normally found in perennial grassland-type habitats such as pastures and grass-legume leys.

109 SummaryIn three field experiments carried out during 1989-91, a permanent sward of pure white clover (Trifolium repens) was established to provide a source of N for winter or spring wheat crops (Triticum uulgare) directly drilled into the legume. Spring-sown wheat failed to compete with the clover, but wheat sown in the autumn established successfully. N fertiliser was applied to all three experiments at rates of 0,50 and 100 kg N ha-' and measurements of grain and whole-crop silage yields were made. Yields were low for all treatments, probably because of the dry conditions prevailing and the low soil N status of the site used. Yield responses to fertiliser were significant, despite the contribution to plant nutrition that the clover was intended to make. A key feature of the work was that the clover survived successive cereal crops and could be grazed and used as an understorey for later crops. Further, response to fertiliser N diminished with a successive crop implying a build-up of available soil N, which measurements confirmed had occurred. Use of the system obviated the need to use pesticides, although reasons for the lack of pest damage were not clear. Key words: Wheat, white clover, low input, understorey, soil N residues clover. Journal British Grassland Society 31:29-35. Heard A J. 1965. The effect of the nitrogen content of residues from leys on amounts of available soil nitrogen and on yields of wheat. Journal of Agricultural Science, Cambridge 64329-334. Hommay G, Briard B. 1988. Apport du pregeage dans le suivi des peuplements de limacos en grande culture. Haliotes 1855-74. Jarvis S C, Barraclough D. 1991. Variation in mineral nitrogen under grazed grassland swards. Plant and Soil Science 138:177-188. Jones L. 1992. Preliminary trials using a white clover (Trifolium repens L.) understorey to supply the nitrogen requirements of a cereal crop. Grass and Forage Scierzce 47:36&374. Jones L, Clements R 0. 1991. Cereals in clover. Crops, 24 August 1991, pp. 16-17. Ladd J N, Amato M. 1986. The fate of nitrogen from legume and fertiliser sources in soils successively Rhodes I. 1991. Progress in white clover breeding. REUR Technical Series, pp. 1-9. Rome: FAO. Watson E R. 1963. The influence of subterranean clover pastures on soil fertility, 1. Short term effects. Williams E D, Hayes M J. 1991. Growing spring cereals in a white clover (Trifolium repens) crop.

A series of laboratory and field studies were done to evaluate a range of leguminous plant species for their feeding potential by adult weevils of the genus Sitona Germar. (Coleoptera: Curculionidae). Three species of Sitona, S. lineatus L., S. flavescens Marsh. and S. hispidulus E all of which are found commonly on white clover (Trifolium repens L.) in the UK were offered a range of 11 legume species, Z repens (white clover, cv. Olwen), T. pratense L. (red clover, cv. Marcom), T. fragiferum L. (strawberry clover, cv. Palestine), T. hybridum L. (hybrid clover, cv. Tetra), T. incarnatum L (crimson clover), T. dubium Sibth. (lesser yellow trefoil), Lotus corniculatus L. (birdsfoot-trefoil, cv. Leo), L. uliginosus Schkuhr. (large birdsfoot-trefoil), Melilotus alba Desr. (white melilot), Medicago sativa L. (lucerne, cv. Europe) and M. lupulina L. (black medick) in two laboratory experiments. The weevils were offered a choice of these legumes in one experiment whilst in the other they did not have a choice of food material.These legumes were also sown in the field and a number of measurements of damage, together with counts of Sitona spp., were made. In the laboratory S. lineatus and S. hispidulus favoured some of the legumes to a greater or lesser extent than white clover. S. flavescens was more restricted in its feeding than the other two weevil species. In the field study S. lineatus invaded the experimental area quickly and tended to favour Medicago spp. and Melilotus spp. Later in the year S. flavescens dominated the sitona fauna on the experiment, with the exception of aggregations of S. lineatus on M. sativa and M. alba. In a separate screen of 5 varieties of white clover (cvs Donna, Menna, Kersey, Olwen and Grasslands Huia), cv. Olwen appeared to be the most susceptible to sitona attack.

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