Diagnosing allelopathy in narrow-leafed lupins

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

What to look for

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.

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

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.

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.

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.

DDLS Seed Testing and Certification

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Page last updated: Tuesday, 20 January 2015 - 10:51am