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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.

Observations at three grassland sites in England and Wales on nine perennial ryegrass genotypes infected or not by the endophytic fungus Acremonium lolii , showed that populations of plant-parasitic nematodes were not reduced on endophyte-infected plants during the two years of the experiment. There was evidence at two sites, where numbers of plant nematodes increased during the trial period, that there were significantly more nematodes on endophyte-infected plants. At the third site, where nematode populations did not increase, there was no difference between endophyte treatments. Nematode population changes on one genotype, known to grow better when endophyte-infected, were similar to the average for all genotypes. In a glasshouse pot experiment, invasion and development of root-knot nematode, Meloidogyne naasi , was the same on endophyte-infected and endophyte-free plants of the responsive genotype. In samples from field plots and in the pot experiment, roots of endophyte-infected plants were larger and probably accounted for the increased nematode populations.

Fungicide seed treatment using benomyl+captan, combined with postemergence sprays of the insecticides chlorpyrifos and omethoate increased herbage yield 10 weeks after sowing in five of eight sowings of Italian and perennial ryegrass. At one sowing, five other fungicide seed treatments—carbendazim+captan, thiabendazole+captan, thiabendazole+thiram, thiabendazole+metalaxyl, and drazoxolon—combined with the insecticide sprays, also increased yield. The insecticides were shown to give good control of shoot-fly larvae, but the yield response to insecticides alone was not as great as that from the combined treatment. As fungicide seed treatment alone increased seedling emergence at one sowing only, possibly the fungicides improved seedling vigour by reducing sub-lethal attacks from soil-borne diseases. The combination of a fungicide and insecticide seed treatment was used at five sowings with no effect.