Winterkilling in puresown ryegrass, the importance of fungal pathogens and possibilities for their control. 1. Results from field trials with natural infection
1986
Winter, W. (Eidgenoessische Forschungsanstalt fuer Landwirtschaftlichen Pflanzenbau, Zuerich-Reckenholz (Switzerland))
Rotten plants, incomplete stands, a reduced number of shoots and a decline in dry matter yield were observed after hibernations of perennial and Italian ryegrass. Isolations from damaged plants showed that the main pathogen was the causal agent of snow mould Monographella nivalis (Schaffn.) E. Muell., asexual stage Gerlachia nivalis (Ces. ex Sacc.) W. Gams et E. Muell., synonym Fusarium nivale Ces. et Sacc. The following fungi were also isolated: Laetisaria fuciformis (Mc Alp.) Burds., synonym Corticium fuciforme (Berk.) Wakef., Gibberella avenacea Cook, asexual stage Fusarium avenacearum (Fr.) Sacc. and Fusarium culmorum (W. G. Sm.) Sacc. The field trials were located at 440 and 630m a.s.l. These elevations correspond to plain and mid-mountain climates, respectively. The tetraploid varieties 'Lipo', 'Tetila', 'Citadel', and 'Bastion' showed a higher level of resistance to snow mould compared to the diploid varieties 'Ursus', 'Lemtal', 'Melino' and 'Pablo'. Tetraploid ryegrasses contaminated the soil with Gerlachia nivalis to a lesser extend than diploid ryegrasses. The influence of the date of cutting and of nitrogen fertilization in autumn on snow mould was also tested. Lowest values at both locations were observed when the last cutting occurred at the end of October. Severity was higher when the last cutting took place earlier (mid September, end of September, mid October). Since parts of stands of the last cutting were strongly damaged by the cold, last cutting should take place in the middle of October, although infection with snow mould will not be as much reduced as if the last cutting was done at the end of October. The plant rotting caused by Gerlachia nivalis was increased with 80 kg N/ha in autumn compared with 40 kg N/ha
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