Pasture nematodes: the major scourge of white clover

This paper reviews current research within AgResearch to reduce the impact of plant-feeding nematodes. Plant-feeding nematodes reduce pasture production by around 15% annually, mainly through their effect on white clover. Nematicide application increases clover yields in pasture by an average 40% and N-fixation levels by over 50%. The problem occurs nationally. When pasture nematode burdens are reduced in established or newly sown ryegrass-white clover pasture, white clover can generally assume dominance during periods of active plant growth. The impact of clover nematodes in reducing nitrogen inputs and forage quality is estimated to exceed $1 billion annually in lost production potential. A gain of 1% in clover performance applied nationally is estimated to be worth up to $48 million. The research programme on pasture nematodes conducted within AgResearch has included evaluation of management practices that may reduce nematode impacts, selection of white clover seedlines for resistance or tolerance to nematodes, and identification of agents for biological control of nematodes within New Zealand pastures. Keywords: clover nematodes, Heterodera trifolii, impacts, Meloidogyne trifoliophila, M. hapla, Pratylenchus spp., Trifolium repens