Control of white rot in dry bulb onions with artificial onion oil

Abstract

SUMMARY Artificial onion oil was evaluated as a soil treatment for control of white rot in onions caused by Sclerotium cepivorum . The treatment was tested at Werribee South in a red brown earth with a sclerotial population of c . 40–100/kg soil; and at Colac in a black clay loam with c . 180/kg soil. Treatments were applied before sowing and their effect on numbers of sclerotia, disease incidence and yield of dry bulb onions determined. At Werribee South onion oil reduced numbers of sclerotia at the 0–10 and 10–20 cm depths in soil, reduced disease incidence and increased yield in comparison with the controls. Onion oil at a concentration of 5% in water and injected (440 litredha) at 10 cm was most effective. The treatment reduced sclerotial numbers at 0–10 and 10–20 cm by 77 and 91% respectively, reduced disease from 57 to 13% and increased yield by 103%. Onion oil at 25% in water had no significant effect on populations of sclerotia or on incidence of disease. In an experiment at Colac, the application of onion oil at 5% in water reduced sclerotial numbers from 187 to 87/kg, but not incidence of white rot.