Effect of ryegrass endophyte in mixed swards of perennial ryegrass and white clover under two levels of irrigation and pesticide treatment

In a small-plot experiment at Hurley, UK, infection of perennial ryegrass with the endophytic fungus Acremonium lolii had no apparent effect on seedling populations and herbage yield of ryegrass and white clover sown in mixture. The plots were maintained under two levels of irrigation with or without pesticide (carbosulfan granules) to study possible interactions with stress due to drought or pest damage. The higher level of irrigation consistently increased yield of both grass and clover during 1989 and 1990, but the effects of endophyte and pesticide on yield were not consistent, nor were the few significant interactions between factors. It is concluded that infection of ryegrass does not appear to increase ryegrass production or to decrease white clover production in the UK, in contrast to reports from New Zealand.