Variations in Infection by Mycocentrospora acerina in Carrot Monoculture Plots at Four Sites during 1985-1995

Infection by Mycocentrospora acerina in carrots was examined in the period 1985-1995 in monoculture plots at four sites with crop-rotation experiments in Norway. At two of the locations, with the most variable climate, the incidence and severity of M. acerina infections on leaves and roots varied most through the different years. At these locations M. acerina attack on the roots was positively correlated with precipitation in July. At one location the incidence of leaf infection corresponded significantly with the incidence on the roots. At one site the length of the storage period correlated with the incidence and severity of liquorice rot in storage.