Pink rot, caused by Phytopthora erythroseptica, is a disease of increasing importance to the potato industry, particularly in key potato production regions of Tasmania, and to a lesser extent, small regions on mainland Australia.

The disease is characterized by pink colouration of the cut tubers, with the rapid rotting of the tubers, whether in ground or in storage, leading to significant yield losses and product downgrades or rejection.

Research in the USA suggests that increasing pH and Calcium levels may reduce early infection of the pink rot pathogen on root and stolon tissue. Additionally, anecdotal evidence in Tasmania suggests the usage of acidifying fertilisers are all contributing to greater pink rot problems. Both these areas are worthy of further investigation via scientific experimentation.

Currently there is no one single control measure to provide effective control of pink rot. Current strategies are also becoming less effective, for instance resistance to metalaxyl (the active ingredient in the fungicide Ridomil) is of particular concern and demonstrates the need to pursue other control options.

To combat this, a new project is underway to investigate how soil pH and nutrition may play a role in reducing the impact of pink rot disease in potatoes, with the results to inform future research in this area. The project will review existing pink rot research and survey growers and agronomists to find out more about their experience of pink rot.

Pot trials and targeted field surveys will be conducted to assess disease factors and analyse soil, particularly the effect of pH, acidifying fertilisers and specific soil chemistry such as calcium on pathogen load and pink rot expression.

This project will provide thorough scientific rigour to determine what role soil pH, acidifying fertilisers and specific soil chemistry play in negating the negative impacts of pink rot disease.

It will look at whether there are any other nutrients of interest (e.g. Boron, Manganese) which show a correlation with pathogen and pink rot disease development, while exploring other potential co-factors such as soil structure, irrigation, compaction, and potato volunteer management that correlate with pathogen and pink rot disease development.

The outcomes will provide direction for research priorities and recommendations related to pink rot management, to maintain productivity and long-term sustainability for the potato industry.

If you would like to get involved in this research, please contact Dr Robert Tegg from the Tasmanian Institute of Agriculture on 0417 738 456 or at robert.tegg@utas.edu.au.
In the meantime, take a look at this fact sheet to find out more about the pink rot pathogen, its lifecycle and management options.

The project Investigating soil pH and nutrition as possible factors influencing pink rot in potatoes – a pilot study (PT19000) is a strategic levy investment under the Hort Innovation Potato – Fresh and Potato – Processing Funds.
The pink rot fact sheet was developed by RM Consulting Group (RMCG), coordinators of Program approach for pest and disease potato industry investments (PT17002), a strategic levy investment under the Hort Innovation Potato – Fresh and Potato – Processing Funds.