Pink Root (Phoma terrestris): Onion Disease & Prevention Techniques

Pink Root And Its Effect On Onion Crops

An onion suffering from pink root (phoma terrestris)Pink Root isn’t a disease that’s just limited to potato crops. It also has a large, wide-reaching impact on New Zealand’s onion crops. 

Also referred to by its binomial name – Pyrenochaeta Terrestris – it can be a pain to eradicate, often surviving in the soil, diseased roots and debris of previous crops for several years. It’s here that the disease often spreads either through the soil itself, or is carried on the dirt’s surface by water.

The disease generally develops in warmer, moist areas. Soil that sits between 24-28c, for example, provides optimum conditions for the growth and development of the disease.

Symptoms & Signs Pink Root May Be Affecting Your Onion Crops

Onion roots infected with the Pink Root often show a light pink colour. Becoming a deeper pink or red over time. Finally progressing to a purple-brown as the roots shrivel and eventually disintegrate.

The crops themselves often appear as though they’ve been affected by severe drought or nutrient deficiencies, though this is actually the result of this troublesome soil pathogen. With the leaves turning a while, yellow and then brown colour before eventually dying out.

Affected onion crops will also start bulbing earlier, with bulbs usually smaller in size compared to healthy, uninfected crops.

Pink Root Prevention & Management Techniques

Ways To Manage Pink Root In Onion Crops

  • Plant crops so that the bulk of the growth occurs before soil temperatures are able to reach ranges that favour Pink Root development.
  • Plan for long-term rotation (4-6 years) with non-host crops including Cereals.
  • Proven, Effective Soil Fumigation Methods.

Image via Texas Plant Disease Handbook

  • Contact Information

    Leicesters Soil Fumigation
    6 Waitane Place
    PO Box 4036
    Marewa, 4143
    Napier, New Zealand

    Phone: +64 6 843 5330
    Fax: + 64 6 843 5158

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