Understanding Stripe Rust in Wheat
October 28, 2024
KEY POINTS
- Stripe rust appears as long yellow to orange linear stripes along wheat leaves and can cause substantial yield and quality loss.
- Mild winters and cool, wet spring conditions favor the development of stripe rust.
- Planting tolerant wheat products is an economical control method of stipe rust.
- Fungicides with triazoles and strobilurins chemistries can provide good to excellent activity against wheat leaf rust diseases.
Introduction
Stripe rust, also known as yellow rust, is a foliar disease of wheat caused by the fungus Puccinia striiformis f. sp. tritici. Rust diseases are the most economically significant fungal diseases in wheat and other cereal crops worldwide. Stripe rust is a problem disease in wheat-growing regions across the United States and Canada along with two other rust diseases, leaf, and stem rust, which make up the rust diseases complex affecting wheat. While wheat is the main host for stripe rust it can also infect barley, triticale, barley grass, and brome grass. Grain losses due to stripe rust can range up to 40% and higher with some fields destroyed if heavy disease pressure is present before heading and goes untreated.1 Higher yield losses can be expected if weather during grain fill is cool and wet, and the wheat product is highly susceptible. Additional losses can occur from poor grain quality because of heavy disease pressure.
Identification, Characteristics, and Diagnosis:
- The fungus Puccinia striiformis f. sp. tritici is the pathogen that causes stripe rust in wheat.
- Initial symptoms appear as small, yellow spots or flecks around the infection site within seven to ten days after infection.
- Stripe rust symptoms eventually develop into long stripes of small yellow or orange pustules that make a blister-like lesion (Figure 1).
- These small yellowish lesions (uredinia) appear in linear rows on the top of the leaf surface.
- These same lesions can also occur on the glumes and on the base of the awns.
- The source of infection often originates from volunteer wheat plants or winter wheat where the pathogen can overwinter on a live host, or spores blown in from southern wheat production areas where stripe rust can overwinter on living host plants.
- Inoculation may also come from nearby early sown fields, later-maturing fields, or from an alternate host species.
- Windblow spores (urediniospores) are the primary method of dispersal for stripe rust.
- Stripe rust infection occurs when temperatures range from 32 to 77 °F.
- Optimum temperature for stripe rust development ranges from 50 to 64 °F.
- Stripe rust infection requires humid and damp conditions with six to eight hours of free water on the leaf surface.
- Hot and dry weather can cause sporulation to stop but can restart when cool, moist conditions return.2,3,4
Management
Stripe rust management starts with scouting wheat fields for rust throughout the vegetative growth stages for the first signs of the rust pustules on the leaf surface. It is especially critical to watch the crop from stem elongation through flowering (Feekes 6 to 10.5) as spread of this disease can happen very rapidly under favorable conditions. The upper leaf tissue, and especially the flag leaf, on wheat plants are critical for providing energy necessary for grain fill, so it is vital to protect these leaves from leaf surface damage and loss due to rust pustules. The potential for yield loss due to stripe rust is reduced if the infection shows up after the wheat crop has reached the dough growth stage of grain development.
Control
Selecting resistant cultivars is the primary method of control for stripe rust in wheat. Controlling volunteer wheat can effectively limit the spread of stripe rust as the causal agent does not survive long on plant debris and requires living leaf tissue from a viable host for survival.
To control stripe rust, a labeled fungicide application may be indicated if it is observed before or during the boot growth stage, the weather forecast calls for cool and damp conditions, and if the wheat product planted is susceptible to stripe rust. Two classes of fungicides, triazoles and strobilurins, are used most often and can provide good to excellent activity against wheat rust diseases. Prosaro® PRO 400 SC fungicide which has three classes of fungicides, pairs powerful preventive and curative disease control with long residual activity for consistent performance across a variety of growing conditions against key cereal leaf diseases including rusts.
To help suppress early stripe rust infections, use a seed treatment. Seed treatments can help protect young plants from rust disease and other threats to plant health and yield potential. Raxil® PRO MD Seed Treatment helps provide consistent, early-season protection and EverGol Energy Seed Treatment Fungicide offers dual modes of action to enable increased stand establishment and early season vigor. For more information about stripe rust and other rust diseases in wheat, read Wheat Rust Diseases.
Sources:
1 Wheat stripe rust. USDA Agricultural Research Service. U.S. Department of Agriculture. https://www.ars.usda.gov/midwest-area/stpaul/cereal-disease-lab/docs/cereal-rusts/wheat-stripe-rust/.
2De Wolf, E.D. 2018. Wheat stripe rust. Kansas State University Research and Extension. Department of Plant Pathology. EP167. https://bookstore.ksre.ksu.edu/.
32020. An overview of stripe rust of wheat. Crop Protection Network. https://cropprotectionnetwork.org/publications/an-overview-of-stripe-rust-of-wheat.
42022. Wheat stripe rust. USDA Agricultural Research Service U. S. Department of Agriculture. Cereal Disease Lab: St Paul, MN. https://www.ars.usda.gov/midwest-area/stpaul/cereal-disease-lab/docs/cereal-rusts/wheat-stripe-rust/.
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