Stem Rust of Wheat and Triticale
Puccinia graminis f.sp. tritici
Dark reddish brown, oval to elongated pustules, full of powdery spores appear on both sides of the leaves sheaths, stems and heads in spring and summer. They tend to appear initially on the leaf and the pustules tend to protrude through both sides of the leaf. At the end of the season the pustules produce black spores as the plant hays off. Leaf and stem surfaces appear torn from ruptured pustules.
The red brown spores will rub off the leaf onto your finger rubbed. The black spores at the end of the season don't rub off.
Species Affected:Infects Barley, Cereal Rye, Durum Wheat, Triticale and Wheat.
Triticale is especially susceptible to Stem Rust.
Biology:Requires warm, 15-300C, moist and humid conditions for infection.
Requires green host plants to survive and cannot survive on stubble or in the soil.
Epidemics are most likely in years when host plants survive over summer.
The red brown spores are infectious whereas the black spores aren't.
Life Cycle:Origin and History:
Can cause complete crop loss in a short time at the end of the season on rare occasions.
Late infections or infections on the head tend to increase screenings rather than reduce yield.
New strains of rust are likely to develop that infect previously resistant varieties.
In 1973/74 season Stem Rust of Wheat caused losses of $100-$300 million in south eastern Australia.
A new strain (Ug99) was found in Uganda in 1999 that is not controlled by current stem rust resistance genes in wheat but was not present in Australia in 2009.
Management and Control:Sow resistant varieties. See Disease Susceptibility of Wheat Varieties
Control volunteer and out of season Wheat, Triticale and Barley.
Seed treatments are not usually effective. Foliar sprays are rarely economic and must be applied early. Spraying is not likely to stop the spread of stem rust in most cases. Propiconazole and triadimefon have shown some worthwhile results when applied just after head emergence.
Fungicide Resistance:None reported.
Related and Similar Species:Leaf Rust of Wheat (Puccinia recondita) has lighter brown spores, circular to oval pustules and tends to be mainly on the topside of the leaf and later in the season occasionally on the sheath. The tend not to noticeably rupture the leaf surface.
Stripe Rust of Wheat (Puccinia striiformis)
Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.