Onion smut is a declared pest in WA
Onion smut is not known to occur in WA and must be reported to DPIRD if found or suspected to be present in WA.
Onion smut (Urocystis cepulae) is a fungal disease of onions. It affects the Allium family, in particular onions and shallots. Spring onions, leeks, garlic and chives are less susceptible to the disease.
What to look for
- Onion smut causes distinctive narrow long dark streaks, usually on the cotyledon or the first true leaf, and the leaves become thickened.
- The streaks are evidence of an infection inside the leaf which later bursts through the leaf surface releasing masses of dark-brown powdery spores.
- Onion plants can only be infected in the first three weeks after germination and most infected seedlings die within 3–5 weeks of infection.
- Diseased plants that survive are stunted, distorted and may not produce a bulb.
- Infection is most likely when the temperature is between 12–25°C during germination.
Damage that this disease can cause
Onion smut causes production losses and may have trade implications for Western Australian onion growers.
Urocystis cepulae (Schltdl.) Rabenh. 1861 is a declared pest under section 12 of the Biosecurity and Agriculture Management Act 2007.
This means that any person who finds or suspects the presence of onion smut must report it to the Department of Primary Industries and Regional Development.
WA’s freedom from onion smut is supported by surveillance and specific import requirements to prevent its entry.
How onion smut survives and spreads
- Onion smut is caused by a fungus that produces many spores as it matures.
- The spores are reported to survive in the soil for up to 15 years even when no onions are grown.
- The disease usually spreads when hosts come into contact with diseased seedlings or soil infested with spores.