Progress towards an integrated control strategy for onion white root rot disease, including the use of artificial germination stimulants

The control of onion white root rot (OWRR) has been demonstrated to be most successful when an integrated management strategy is adopted. Disease incidence was reduced from 58% in early sown high density onions grown without fungicide application, to 0.3% in late sown low density onions grown with a single fungicide application. Differences in disease incidence of up to 70% have been recorded between cultivars. A degree of control with a fungicide treatment was demonstrated using Folicur-treated Lime Super which was drilled with the seed. An artificial germination stimulant, diallyl disulphide (DADS), has been incorporated into the soil and reduced sclerotia populations, and has resulted in a 45% reduction in disease levels. Integrating the fungicide treatment with DADS treatment, has resulted in the production of a commercially acceptable crop, reducing disease levels from 75% to 11% and increasing yield from 15t/ha to 44t/ha when compared to onions grown in untreated soil and without fungicide application. Another control option being investigated is the use of Eucalyptus leaf mulch which has shown a very high level of control in pot studies.