Parsley summer root rot, or SRR, is a disease complex affecting all parsley-growing regions of Australia. Crop losses from SRR can be as high as 100 per cent – a concerning figure for the parsley industry, which has an estimated annual production value of around $34 million.

Both immature and mature plants can be affected, with characteristic symptoms including leaf chlorosis, plant stunting, browning and rotting roots, loss of secondary roots and – in some instances – a spongy soft rot developing around the crown. Plants eventually wilt and collapse if the crown rot and root damage is severe.

A research project funded through the Hort Innovation Vegetable Fund has investigated SRR to determine the causal pathogen (or pathogens) of this disease and understand its epidemiology, particularly in relation to any predisposing practices or environmental conditions.

Through a combination of research and field work, including surveying 19 farms across four states to collect plant samples affected by SRR and interviewing growers about their experiences, the project team has investigated the causes and management of this disease complex.

Among its findings, the study has identified that improved farm biosecurity and crop hygiene is a basic strategy to minimise the risk of SRR, and that improved production technologies such as protected cropping in soilless systems could be applied to avoid the one major environmental predisposition: excess soil moisture.