Post-emergence damping-off in Poa pratensis and its relationship with seed weight and seedling establishment.

Seed lots representing 30 cultivars of P. pratensis, sown at 30 g/m2 were assessed for post-emergence damping-off severity and establishment in a field experiment. Diseased shoots from 10 of these cultivars revealed the presence of Fusarium culmorum or Cladochytrium spp. in > 95% of cases. Cultivars showing a higher incidence of 1 pathogen tended to have a lower incidence of the other. On av., post-emergence damping-off was more severe when cultivar seed lots with lighter seeds (more seeds/m2) were sown. Initially there was a positive relationship between reflectance ratio meter readings (used to assess establishment and severity of disease) but eventually plots which had high levels of disease tended to be less well established. Time taken to reach 50% germination on damp filter paper was weakly, but significantly, negatively associated with severity of post-emergence damping-off. Av. seed DW and germination characteristics on damp filter paper were associated, to different degrees, with initial reflectance ratio assessments.