Effects of barley yellow dwarf virus on simulated swards of Nui perennial ryegrass

Abstract

Abstract Total herbage produced from simulated swards of perennial ryegrass-white clover over aperiod of 18 months was not significantly affected by infection of the ryegrass with barley yellow dwarf virus (BYDV). However, seasonal production was affected by the virus. In summer when drought did not limit growth, virus-free swards outyielded those in which all and those in which half the ryegrass plants were infected with BYDV. In winter, those swards in which half the ryegrass plants were infected with virus outyielded both the healthy and the wholly infected swards. Clover production was greatest in swards where all ryegrass plants were infected with BYDV. In simulated swards of pure ryegrass, healthy swards outyielded wholly-infected swards by 22.4% over the 18-month period.