Argentine stem weevil (Hyperodes bonariensis Kuschel) resistance in perennial and hybrid ryegrasses. I. Field resistance in perennial ryegrass (Lolium perenne L.).

Abstract A high level of host plant resistance to Argentine stem weevil (ASW) (Hyperodes bonariensis Kuschei) has been recorded under field conditions in a line of perennial ryegrass (Lolium perenne L.) collected from the Takapau district in Central Hawkes Bay. When compared with the commonly sown cultivars of perennial ryegrass, ‘Grasslands Ruanui‘ and #x2018;Grasslands Nui‘, this ryegrass suffered minimal adult ASW damage, harboured low number of eggs and larvae, and hence suffered low levels of larval damage. Another ryegrass cultivar, Ellett, was also found to be more ASW resistant than Nui but its superiority over this cultivar was less marked than that recorded for ‘Takapau‘. The production and persistence of Ruanui and Nui swards was severely affected by ASW damage and as a result these became white clover (Trifolium repens L.) dominant whereas swards of ‘Takapau‘ ryegrass persisted as well balanced grass–clover mixtures. The production of Nui and Ruanui ryegrass was similar but was approximately 6...