Glume blotch in cereal crops is often confused with Septoria. At the heading stage, when the disease is typically first noticed, glume blotch appears on upper portions of the crop as dark – and sometimes purplish – blotches and streaks.
Similar to other diseases that occur at heading, glume blotch poses one of the greatest threats to wheat and other cereal crops, from the southern U.S. to the western wheat-growing provinces of Canada. In some states, glume blotch is one of the main causes of poor-quality seed production and yield loss.
Glume blotch disease is caused by the fungi Stagonospora nodorum and can also affect other small grain crops such as barley, rye and oats. It’s part of the Septoria disease complex that advances from early season to flag stage through heading. If management precautions are in place, disease development is discouraged.
Identification and Lifecycle
Glume blotch can be tough to distinguish from Septoria and other leaf spot diseases. Although glume blotch can infect both leaves and heads, it’s not typically recognized until heading.
The lower leaves of overwintered wheat plants usually show the first signs of glume blotch. Lesions first appear as dark brown flecks with a yellow margin. At the heading stage, glume blotch appears on upper portions of cereal crops as black or dark-brown blotches and streaks, sometimes appearing purple in color.
Temperatures ranging from 68 to 82 degrees F and accompanied by cool, wet, humid and windy weather enhance glume blotch infection and allow spores to spread among canopy layers. As temperatures warm, the disease will decrease.
Wheat glume blotch overwinters on crop residue and in infected seed. The disease begins as spores that create leaf spot lesions over a period of 10 to 20 days. As the disease moves from lower to upper leaves, new spores splash onto leaves and wheat glumes, which become infected with glume blotch.
When lesions severely infect upper leaves and cereal heads, wheat glume blotch shuts down photosynthesis and uptake of valuable plant nutrients. Seed fill is diminished, resulting in shriveled grain at harvest that can be lost with chaff. Research shows that wheat yields can be severely reduced – as much as 30 percent – by glume blotch.
Managing Glume Blotch
Farmers have several options to manage glume blotch in wheat and other small grains such as barley.
All wheat and cereal varieties have some susceptibility to glume blotch disease, so choose varieties that offer some level of resistance to protect yields. Excellent disease resistance is not available to manage all disease threats in high-yielding cereal varieties. It’s best to select two or three high-yielding varieties that offer the best resistance to common diseases found on your individual farm.
When scouting for diseases, start early and check for the presence of both foliar and cereal head diseases. Glume blotch appears on head portions of cereal crops as black or dark brown blotches and streaks, sometimes appearing purple in color.
Frequent scouting, beginning at the seedling stage, helps you time a fungicide application, which will vary by geography. It also provides information to help you select appropriate disease management practices for future crops. If you suspect glume blotch, take samples and work with your county Extension agent to confirm a diagnosis. Crop identification guides are also helpful.
The glume blotch disease fungi can survive in infested crop residue for several years. Cultivation can break down crop residue that harbors certain diseases, but it is not advised in dry geographies that need to conserve moisture. Plant disease-free, certified seed. Controlling weeds during preplant, at planting and throughout the growing season also helps protect against some diseases and insect pests.
Excellent glume blotch control can be achieved with commercially available fungicides. In some states, experts recommend a fungicide spray when 3 of 5 scouted locations within a field show 25 percent of leaves with one or more lesion. Fungicide application timing should be aimed at keeping the upper leaves of the wheat plant disease-free, allowing full potential for grain fill. The flag and flag-1 stages of development are the most important times to control cereal diseases with fungicide applications. The leaves in these stages are critical to photosynthesis and occur close to the time of plant heading.
Bayer Solutions for Glume Blotch
Prosaro® fungicide provides broad-spectrum disease control to help maximize yield and profit potential in wheat by protecting your crop from both scab and leaf diseases, including glume blotch. Prosaro stops the penetration of the fungus into the plant and the spread of infection within the plant. Prosaro inhibits the reproduction and further growth of the fungus. It provides powerful control of glume blotch, leaf rust, septoria leaf blotch, stem rust and tan spot in wheat, and net blotch, scald and spot blotch in barley.
For information on Bayer’s portfolio of products to help cereal growers maximize yields and protect crops, contact your local Bayer representative.