Ug99 wheat stem rust

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Exotic to Australia

Life form: Fungus
Origin: Uganda
Distribution: Africa (Egypt, Eritrea, Ethiopia, Kenya, Mozambique, Rwanda, Tanzania,
South Africa, Sudan, Uganda, Zimbabwe) and Middle East (Iran, Yemen)
Features: Reddish brown, powdery, oblong spore-producing pustules characteristic
of wheat stem rust
Pathways: Trade/movement of infected plants, windblown spores
At risk: Grain (wheat, barley, oats and rye)


Ug99 pathotype of Puccinia graminis is a fungal pest causing wheat stem rust that poses a high biosecurity risk to the wheat industry. It could cause total crop failure to Australia’s economically important cereals wheat, barley, oats and rye.

A number of pathotypes of wheat stem rust are already present in Australia, and resistant wheat varieties have been developed for those. Unfortunately, Ug99 has overcome many wheat resistance genes, and can attack all parts of the plant that are above ground. However, stem and leaves are most impacted by the fungus.

Puccinia graminis has a complex life cycle. In countries where this species undergoes its entire life cycle, it produces five spore types and has two host plants – cereals and common barberry (Berberis vulgaris). The common barberry is rare in Australia, and so the fungus cannot fully complete its lifecycle.

An incursion of this fungus could severely disrupt international trade and have a major economic impact on our agricultural industry as a major exporter of wheat.

How to identify Ug99 (a pathotype of Puccinia graminis f.sp. tritici)

Everyone needs to keep an eye out for stem rust symptoms of Ug99.

Stem rust is characterised by reddish brown, powdery oblong pustules on stems as well as leaves, leaf sheaths and heads.

There are other wheat rust diseases that have similar symptoms to Ug99. These include: leaf rust (Puccinia triticina) which causes small brown circular pustules that are normally on the upper leaf surface, but can also be on the wheat sheath in severe epidemics; and stripe rust (Puccinia striiformis f.sp. tritici) characterised by long stripes of small yellowish orange pustules on the leaves.

In Australia if stem rust is detected on any wheat lines that were thought to be resistant to wheat stem rust, they need to be tested for Ug99.

The ability of rust plant pathogens to spread rapidly makes these pests extremely difficult to eradicate. Rust spores can spread large distances with wind and human-assisted movement of infected plant material and contaminated clothing.

Symptoms of wheat rust Ug99 on stems of wheat (source: David Mowbray/CIMMYT)
A single wheat steam showing symptoms of wheat rust Ug99. There are reddish brown pustules growing all over the stem of the wheat.
Symptoms of wheat rust Ug99 on the leaves (source: R.L Croissant,
Two leaves of the wheat plant showing the symptoms of wheat rust. The same reddish brown pustules also can grow on the leaves. Only have a couple of parts of the leaf is infected in this picture.
Ug99 lifecycle (source:…)
Diagrammatic drawing of the lifecycle of Ug99. There are 5 spores types being produced teliospores, basidiospores, pycinospres, pycnospore and aeciospores. These form on two hosts.
Stem rust spores visible on wheat head (source: Ida Paul,

Close up of a single wheat head showing the tiny reddish brown spore rusts that are visible.


Importers and travelers

Pathotype Ug99 of stem wheat rust is a production pest and will also affect leaves and grain.
If you work around imported goods, you need to look for grain that is infected with reddish brown, powdery pustules. Also ensure that all imported agricultural machinery is clean and free of wheat seeds and other contaminants.

It is important that people and luggage, clothing and shoes are clean and free of soil or plant material when entering Australia.

Growers and grain handlers

It is important that growers monitor their crops regularly to ensure early detection, especially during warm spring conditions.

Walking through cropping paddocks in a ‘W’ shape checking 5 plants at 10 different locations can help with early detection. Try to keep checking every 7-10 days. Every stage of growth should be monitored!

Protect your farm from biosecurity risks, practice good on-farm biosecurity and regularly monitor your fields.

Keep Ug99 (Puccinia graminis f.sp. tritici) out of Australia

All Australians and international tourists have a role to keep out exotic pests and diseases.

Australia remains free of this exotic pest. We need your help to keep it this way.

Check what you can and cannot bring into Australia, whether you are a:

Our wheat industry depends on you!

Australia has a well-deserved reputation for marketing quality wheat to the world. This favorable status depends on good biosecurity practices, including growers and grain handlers inspecting their wheat, and taking action if they see any problems.

Import restrictions and biosecurity measures

Some items, by law, are subject to certain import conditions to be allowed into Australia. Please check the Biosecurity Import Condition System (BICON).

Be aware of any Ug99 biosecurity measures that may be in place for incoming goods and conveyances. Industry advice notices are reviewed regularly and could change.

Secure any suspect specimens

Containment is critical.

If you suspect you have seen Ug99 in cereal crops, take a photo and record the location.

Report detections of exotic pests

Any detections of Ug99 must be reported to the authorities.

Import community

If you receive or work around goods imported from overseas, including mail, you need to be vigilant to stem rust symptoms from Ug99 and other exotic pests.

If you see an unusual pest, secure the goods to limit the movement of the pest and immediately report it to the Department of Agriculture's SEE. SECURE. REPORT. Hotline 1800 798 636 or by using the online form.

Growers and home gardeners

If you see symptoms of stem rust from Ug99 or anything unusual, report it to the Exotic Plant Pest Hotline 1800 084 881. This will put you in touch with the Department of Primary Industries or agriculture in your state or territory.

When reporting your concern, you will be given advice on handling the specimen and what to do next until an officer can investigate.

Additional information

Last reviewed: 13 December 2019
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