What was it all about?

This project developed a soil DNA test and improved management strategies to help onion growers better assess and manage the risk of onion white rot. The DNA test can detect and measure onion white rot levels in soil before planting and is now available through the PREDICTA Hort Veg service. This gives growers a practical way to assess onion white rot risk before planting and make more informed decisions about crop planning and disease management.

Growers and researchers evaluated a range of management options to reduce disease pressure and improve crop outcomes. Participating businesses contributed information that helped assess onion white rot levels and evaluate different treatment options. Outputs from the project included the soil DNA test, a plain-English “In a Nutshell” summary featuring four case studies, and a recorded industry workshop.

Onion white rot remains one of the most damaging diseases affecting onion production and can be difficult to manage once established in soil. Research confirmed that tebuconazole applied at sowing remains the foundation treatment for disease control, while the recently registered fungicides Luna Experience and Intuity provide additional management options as part of an integrated disease management program.

A commercially available garlic extract, NemGuard, was also assessed as a germination stimulant to help reduce disease inoculum in soil, but it did not lower onion white rot levels under the conditions tested. Together, the findings highlight the value of combining soil testing, targeted fungicide use and ongoing monitoring to support more effective management of onion white rot.