VG08026 Pythium control strategies – overview

Pythiums have been described as the “common colds” of plants. They are ubiquitous in vegetable crops and the damage they cause often goes unnoticed except in extreme situations, e.g. damping off disease of parsley seedlings and cavity spot of carrots.

Pythiums are fast growing and reproduce rapidly. They damage root hairs and lateral roots, which impairs water and nutrient uptake and reduces productivity.

The aim of this 3 year project is to determine the role of Pythium in causing root rot and canker; identify predisposing factors to disease and disease control strategies using P. sulcatum and parsnip, parsley & coriander as the model pathogen and hosts.


Liz Minchinton Dolf de Boer
Joanna Petkowski Len Tesoriero
Victor Galea

Pythium root rots of Apiaceae and other vegetables - 2009
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Environmental effects :

Pythium induced root rots are most noticeable in field grown Apiaceae vegetables over the cooler months in southern Australia, especially when the soil temperatures drop to 10ºC or less.

Parsnips: Field trials for VG05045 showed that controlling Pythiums during winter reduced canker in parsnips sown in February and harvested in October.

Parsley: Trials for VG04025 showed that when temperatures were low, severe damping-off developed about a week after rain but not after irrigation.

Chemical control

The fungicide metalaxyl can control cavity spot of carrots, damping-off disease in parsley and parsnip canker. However, the high risk of fungicide resistance and biological break-down of this chemical in soil means that finding other control options should be a priority.

Hydroponics :

Because pythiums are water-borne pathogens, major crop losses can occur in hydroponic vegetable production.

The controlled environment of a hydroponic system lends itself to managing Pythium by manipulating the temperature and chemistry and adding biological control agents.

Acknowledgements :

The authors acknowledge the financial contributions from the National Vegetable Levy (AusVeg), Horticulture Australia (HAL) and the Federal Government which made this work possible.

Special thanks to vegetable growers Frank and Angelo Lamattina and Darren Schreurs for providing the field site & crops.

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