VG08426 Parsnip – Pythium Notes 2010

Pythiums have been described as the “common cold” of plants. They are ubiquitous in the vegetable industry and their damage goes unnoticed unless extreme, such as damping off of seedlings and cavity spot of carrots.

Pythiums attack root hairs and lateral roots impairing water and nutrient uptake thus reducing productivity in the early stages of crop production.

This project update was presented to a workshop meeting of vegetable growers and agronomists at Cranbourne, Victoria in March 2010.


Liz Minchinton

Dolf deBoer

Joanna Petkowski

Des Auer

Len Tesoriero


VG08026 - Identification of IPM strategies for Pythium induced root rot complex in Apiacae vegetable crops - Workshop Notes 2010
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  • On sandy soil metalaxyl effectively controlled canker. This supports the view that Pythium species are important in the development of canker.

  • On clay soil, neither metalaxyl or strobilurin couldt control the disease, due to enhanced degradation of this chemical in the soil.

  • Metalaxyl degradation has been reported to occur in slightly alkaline soils under anaerobic conditions.

  • Clay soils may require other options for disease management such as aeration and improved structure using appropriate rotation crops e.g. plants with deep root systems. Rotation crops are likely to assist control

Monthly surveys of pathogen genera at trial sites at Clyde and Devon Meadows :

  • This study confirms the view that Pythium species are involved in the development of canker on parsnip roots, perhaps by providing a means of entry of other pathogens or saprophytes.

    Only Pythia were isolated early in the coolest period of the cropping season (no competition from other pathogens)

  • Only Pythia were isolated early in the coolest period of the cropping season (no competition from other pathogens) .
  • Pathogenic fungi (Fusarium, Phoma, Rhizoctonia & others) entered crops after the cool period.

    Pathogenic fungi (Fusarium, Phoma, Rhizoctonia & others), entered crops after the cool period

Testing the pathogenicity of different fungi to parsnip :

  • F. oxysporium proved to be the most pathogenic of the fungi tested on parsnip roots, but produced relatively small lesions. Similar symptoms have been observed in the field.

  • Pythium sulcatum was not particularly pathogenic on the mature parsnip roots.

  • This experiment will be repeated on parsnip seedlings to determine whether infection by Pythium depends on the age of the plant.

Efficacy of biological control agents for Pythia in hydroponic Coriander crops :

  • SAR (Systemic Acquired Resistance) – resistance activator (Bion™) had no effect, but was phytotoxic.

  • Bacillus subtilis (Fulzyme Plus™) provided 3 week protection.

  • Pythium oligandrum (mycoparasite) had no effect though this was a ‘home grown’ preparation.

Acknowledgments :

The authors wish to thank Frank and Angelo Lamattina and Darren Schreurs for providing the field site & crops.

Funding was provided by Australian vegetable growers (through the R & D levy) and the Department of Primary Industries, Victoria. The Australian Government provides matched funding for all HAL’s R&D activities.

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