Tolerance of white clover cultivars to stem nematode (ditylenchus dipsaci)

Observations were made in a white clover (Trifolium repens L.) evaluation study on differential cultivar resistance to stem nematode [Ditylenchus dipsaci (Kuhn) Filipjev] damage in 1983. The cultivars (followed by country of release) were: ‘Grasslands Huia’ (New Zealand), ‘Grasslands Pitau’ (New Zealand), G18 (New Zealand), ‘Aran’ (Ireland), ‘Bianca’ (Belgium), ‘Donna’ (United Kingdom), ‘Menna’ (United Kingdom), ‘Nesta’ (United Kingdom), and ‘Sabeda’ (United Kingdom). In pure swards, G18 and Sabeda showed least damage and Pitau and Huia showed most damage. In mixture with perennial ryegrass (Lolium perenne L.), Pitau and Huia had the lowest clover ground cover and large, conspicuous, clover-free patches developed in Pitau plots. Stem nematode damage appeared in early September, was greater in October, and disappeared by late November. Pitau was slowest to recover from the damage. Our observations suggest that stem nematode infestation contributed to poor stand vigour of Pitau and that the development of G18 represents an advance in breeding for nematode resistance. Susceptibility to stem nematode will probably not limit the adaptability of the overseas cultivars to Waikato conditions.