Diagnosing allelopathy in cereals
Allelopathy is an uncommon disorder of germinating plants caused by a toxins in the soil that have leached from plant residues.
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.
Paddock
- Seeds germinate but roots and shoot are deformed and spindly.
- The emerging shoot frequently wanders through the soil without reaching the surface.
- Plants that do emerge are poor and rarely produce grain.
Plant
What else could it be
Condition | Similarities | Differences |
---|---|---|
Diagnosing deep seeding in cereals | Reduced germination, weak seedling and/or older leaf death | Surviving plants recover |
Diagnosing poor seedbed soil structure | Reduced germination, weak seedling and/or older leaf death | Surviving plants recover |
Diagnosing poor seed-soil contact in crops | Reduced germination, weak seedling and/or older leaf death | Surviving plants recover |
Diagnosing pythium root rot in cereals | Root browning, stunted plants. Phytotoxins that cause allelopathy may predispose plants to pythium root rot | Mostly in cold wet conditions, distinctive root lesions |
Root chewing insects
|
Reduced germination, weak seedling and/or older leaf death | Chewed root or lower stem |
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.
- Toxins that cause allelopathy predispose the plants to fungal root rot.
- 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.
Management strategies
- 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
Page last updated: Tuesday, 20 January 2015 - 9:32am