Fig. 3.

Relationship between Broadbalk and national survey data over the period 1970–2003. Broadbalk data are ratios of P. nodorum to M. graminicola DNA from winter wheat leaves/stems at harvest of the Broadbalk experiment. National disease survey data were collated from 300–400 randomly selected commercial crops in England and Wales in each year (including crops with different cultivars, agronomic regimes, and geographical variation in soil types and meteorology) (refs. 3–5 and the Department for Environment, Food and Rural Affairs, Central Science Laboratory). These data are ratios of visual severity of diseases caused by P. nodorum and M. graminicola on penultimate leaves of winter wheat at grain-fill (growth stage 73–75). Linear regression, r = 0.84; P < 0.001.