The disease onion white rot – Sclerotium cepivorum – is a serious problem in bunching Allium crops, which include spring onions and shallots, sometimes causing crop losses of up to 50% in eastern Australia.
Before this project began vegetable growers used the fungicide procymidone to manage white rot, but complained that they were not getting good control.
The purpose of this project was to evaluate chemical and biological treatments for the control of the disease onion white rot on bunching onion crops.
This project has provided vegetable growers with more control options and an integrated strategy for the sustainable control of this soil-borne disease and to better inform them of the most appropriate and effective use of chemical and biological treatments for disease management on their farms.
This project has successfully developed new treatments which can be used alone or as part of an integrated package by vegetable growers to control onion white rot of bunching onions in their farms.
The project also provided valuable information that will assist vegetable growers to make informed decisions about the use of the biological control Trichoderma for managing onion white rot and soil health.
More successful control of white rot will be obtained when using an integrated management strategy that incorporates different treatments, strategies and tactics for disease control.
In general, there are three key strategies that growers can use to obtain effective and sustainable control of white rot on bunching onion crops.
The project developed valuable information that will assist vegetable growers to make informed decisions about the appropriate use of the biological treatment Trichoderma for managing white rot and soil health in vegetable farms.
In sandy soils, the use (in-furrow) of pellets containing humic acids (eg Agrolig, AgChem) will be required to help Trichoderma to grow better in these soils with low levels of organic matter.
Trichoderma growth is inhibited by nitrogen released from fertilizers and fresh composted chicken manure.
Therefore, these materials should not be applied for at least 2-3 weeks before and after sowing to allow Trichoderma spores/propagules to germinate and establish in soils.
Field rates of Filan and low-nitrogen soil amendments can be applied to soil treated with Trichoderma.
Trichoderma can be applied to soils treated with DADS several weeks after it was injected into soil.
In summary, in the short and medium-term, onion white rot can be managed with new fungicide treatments and biological controls, when possible.
For the long-term, the challenge remains to secure supply and registration of synthetic DADS for Allium industries in Australia.
The future of onion white rot research in Australia will be directed towards the development of cost-effective soil treatments to eradicate sclerotia of S. cepivorum and other important sclerotial pathogens of onions and vegetable crops from soils and development of integrated approaches for sustainable disease control.
There were many people and organisations that provided assistance to make this research possible. They include:
This project was commissioned by Horticulture Australia Limited with funds frrom the Vegetable R&D levy..
The Australian Government provides matched funding for all HAL’s R&D activities.