Basil Downy Mildew management options – is it seedborne?

Abstract

Basil downy mildew (Peronospora belbahrii) was identified for the first time in Australia in 2017. Since the first report, the fungal organism spread rapidly with incidences reported in all states other than Tasmania and Western Australia. There have been significant impacts on both field and glasshouse grown crops of basil with growers unable to manage the level of infection, this led to a shortened growing season and a reduced number of picking cycles.
The purpose of the research study was to examine whether seed was the primary source of disease spread in Australia and to identify potential management strategies for the disease The research results showed no evidence to suggest that the commercial basil seed used was infested with basil downy mildew. However, the overseas literature states that the level of seed detection can be as low as (0.03%), therefore a higher sampling frequency would be required to confidently conclude that seed is or isn’t infected.
The project delivered on a number of aspects:
• The successful detection of the basil downy mildew (BDM) organism in seed (known field infection) using molecular technology.
• A technique developed to inoculate plants artificially which could be used to determine cultivar susceptibility to the disease and to screen products for disease management (fungicides/biologicals).
• Molecular assays tested and implemented that can detect the BDM organism in pure form, infected foliage and in seed.
• Provision of advice in relation to chemical permit applications, which has led to an additional five fungicides permitted for use to manage BDM.