White rot caused by the fungus Sclerotium cepivorum Berk., is a serious disease of onions and garlic in the Lockyer Valley in southern Queensland. Options for controlling the disease are limited. Experiments and trials were conducted to determine the effect of planting time on disease appearance, the relative effectiveness of applying fungicides before infection and after infection, the influence of different irrigation strategies on disease severity and the interaction between the numbers of sclerotes in the soil and yield losses, with the aim of predicting potential yield losses in a particular field before planting.