Three different rust diseases occur on wheat and other small grains in the High Plains: stem rust, leaf rust, and stripe rust. The diseases are named for the dry, dusty, yellow-red spots and stripes found on infected plants. Rusts are caused by the fungi Puccinia graminis f. sp. tritici (stem rust), P. recondita f. sp. tritici (leaf rust), and P. striiformis (stripe rust). Numerous pathogenic races of each pathogen exist, and some can infect wheat, barley, rye, and other grasses. Rust fungi have a complex life cycle that involve alternate hosts and as many as five different spore stages. The pathogens overwinter on living hosts (small grains or alternate hosts) and as dormant teliospores within plant debris (leaf and stem rusts). Infection by the stem, leaf, and stripe rust pathogens occurs when moisture is abundant and temperatures are between 60 to 70ºF, 60 to 72ºF, and 37 to 60ºF, respectively.
Rust disease symptoms include dry, dusty, yellow-red spots and stripes found on infected plants. Uredinia, the fungal fruiting bodies that produce urediniospores, are most abundant on upper leaf surfaces (leaf rust), stems, leaf sheaths, and occasionally on glumes, awns, and even seed (stem rust), and leaves and heads (stripe rust). Uredinia of stripe rust are often arranged in lines or stripes that can extend the entire length of the leaf blade. Rust diseases reduce photosynthetic area, increase transpiration, reduce feed quality, and reduce plant vigor. Overall, they reduce root growth, yield, and seed filling, and can make plants more susceptible to other diseases.
No biological control strategies have been developed for rust diseases of wheat.
Resistant varieties effectively control rust diseases, but new races of the rust pathogens quickly develop that can overcome single-gene resistance. “Slow rusting” varieties are available and appear to have more stable resistance to rust diseases. Sanitation of volunteer grains and alternate hosts can reduce pathogen survival, but epidemics can still occur from urediniospores blown in from long distances. Resistant varieties are available and may become susceptible with changes in the virulence of rust pathogen. Variety mixtures and multilines each carry different rust resistance genes, can reduce damage.
Several fungicides are available that effectively control rust diseases, but may not be economical for some production systems.
Product List for Stem Rust, Stripe Rust and Leaf Rust:
Pesticide |
Rate per Acre |
Application Frequency |
Remarks |
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Manzate 75DF |
2 lb |
7-10 days; beginning early heading |
Maximum of 3 applications; 26 day PHI; grazing restrictions |
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Triazole |
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PropiMax EC |
2-4 fl oz |
One application. Apply no later than Feekes 8 |
40 day PHI |
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Tilt 3.6E |
2-4 fl oz |
1 spray at Feekes 8 |
40 day PHI |
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Strobilurin and Strobilurin/Propiconazole |
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Headline |
6-9 fl oz |
10-14 days, begin at Feekes 10.3-10.5 |
Maximum of 2 applications; 14 day PHI |
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Quadris |
6.2-15.3 fl oz |
10-14 days, begin at Feekes 10.3-10.5 |
Maximum of 2 applications; 45 day PHI |
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Stratego |
10 fl oz |
10-14 days, begin at Feekes 8 |
Maximum of 2 applications; 35 day PHI |
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Quilt |
14 fl. Oz. |
14 days. Apply no later than Feekes 9 for barley, rye, triticale and Feekes 10.5 for wheat. |
Maximum of 2 applications; 45 day PHI |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Small Grains, Disease, Stem Rust, Stripe Rust, Leaf Rust
Date: 9/22/06