Diagnosing allelopathy in narrow-leafed lupins

Allellopathy is a disorder of germinating plants caused by plant phytotoxins.

Plants may emerge then curve back into the soil
The hypocotyl is thickened and bent
Affected plants often germinate in or near organic matter
Reduced plant density in the foreground due to allellopathy in seed stored with green wild radish seed

What to look for

    Paddock

  • Poor germination and spindly seedlings in patches, rows or scattered plants where the plant is in contact with plant residues.
  • Severity may vary with soil type or amount of plant residues.

    Plant

  • Seeds germinate but fail to reach the surface, or appear later with yellow cotyledons and new growth.
  • The hypocotyl is thickened and bent, often to the extent that the plant fails to emerge or emerges then re-enters the soil.
  • Roots are grossly distorted and reduced.
  • Affected seedlings usually slowly die, leaving an overall reduction in plant density

What else could it be

Condition Similarities Differences
Diagnosing poor quality seed in narrow-leafed lupins Reduced and staggered germination. Malformed seedlings Allelopathy affected plants remain pale, distorted and stunted
Diagnosing seedbed constraints in narrow-leafed lupins and field peas Reduced and staggered germination The problem is more likely to vary between rows, and with changes in soil or landscape position. Established plants grow normally.
Diagnosing water repellence Reduced and staggered germination The problem is more likely to vary between rows, and with changes in soil type.
Diagnosing waterlogging in narrow-leafed lupins and field peas Reduced and staggered germination Waterlogged and saline areas are often clearly defined, and the problem is ongoing.

Where does it occur?

  • Phytotoxicity most often results from toxins leaching into the soil from dead or dying plants in the following situations:
  • Allelopathy from summer weeds such as goosefoot (Chenopodium pumilio).
  • Where previous season's crop or pasture residues are left in contact with the seed during seeding.
  • Where crops are sown into weedy seedbeds sprayed with a herbicide before the weeds have died.
  • Toxicity tends to be worse where crops are sown in a moist drying seedbed, where there is insufficient rainfall to leach toxins through the soil profile, and in cold, cloudy weather.
  • Toxins that cause allelopathy predispose plants to fungal root rot.
  • Lupins have been affected in a silo by toxins released by green wild radish seed that was harvested with the seed.

Management strategies

Weed and pasture control
Weed and pasture control
  • There is no treatment for affected plants.
  • Allelopathy can be avoided by minimising summer weed growth and plant residue contact with the seed at sowing.

Where to go for expert help

Geoff.j Thomas
+61 (0)8 9368 3262
DDLS Seed Testing and Certification
+61 (0)8 9368 3721
Page last updated: Tuesday, 20 January 2015 - 10:51am