Wheat Diseases: Updated Facts and Pictures_Part 1

Septoria tritici blotch: This is usually one of the various diseases to show up during the wheat seasons. It develops best under cool, wet conditions, with symptoms commonly detected on lower leaves. Initial lesions appear as yellowish or chlorotic flecks that later enlarge into irregular, brown-to-reddish brown lesions. As the lesions age, the centers become bleached with gray or ash-white centers, with small, dark-brown to black specks. The presence of these specks, called pycnidia, is the most reliable characteristic to help tell this disease apart from other disease such as Stagonospora leaf blotch and tan spot that typically develop later in the season. Read more about Septoria and other leaf blotch diseases of wheat at:

http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/PLPTH-CER-07_Leaf_blotch_diseases_of_wheat_2016.pdf

Powdery mildew: This is another disease that usually shows up early in the season. Wheat plants are most susceptible during periods of rapid growth, especially between the stem elongation and heading growth stages. As a result, mildew is most prevalent on the lower leaves of susceptible varieties in late April or early May, especially when the wheat stand is dense (heavy tillering) due to high nitrogen application and seeding rates. Powdery mildew is one of the easiest foliar diseases to identify since it is the only disease that produces powdery, fluffy, white-to-gray fungal growth on leaves, and eventually on stems and even heads. Read more about wheat powdery mildew at:

http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/PLPTH-CER-11_Powdery_Mildew_of_Wheat_2016.pdf

Leaf RustLeaf Rust: Unlike powdery mildew and Septoria tritici blotch, leaf rust typically develops toward the latter half of the wheat season. This is mainly because the fungus that causes this disease does not usually survive in Ohio, and as such, spores have to be blown up from the south. However, under mild winter conditions similar to those we experienced this past winter, the fungus survives on volunteer plants and may infect the crop just as early as powdery mildew and Septoria. Leaf rust is the most common of three rust diseases that affects wheat, and can be identified by the presence of rusty-colored pustules erupting through the leaf surface. It can be distinguished from other leaf diseases by rubbing the leaves and looking for the rusty color on your finger.  Read more about rust diseases of wheat at:

http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/PLPTH-CER-12_Rust_diseases_of_wheat_2016.pdf

Septoria, powdery mildew, and leaf rust are all capable of substantially reducing wheat yield and test weight, especially if your cultivar is susceptible and the flag leaf is damaged between Feekes 8 and Feekes 10.5, before grain fill is complete. Scout fields and look for these diseases and use this information to help you make your fungicide application decision. This would be a good time to apply a fungicide to protect the flag leaf if your cultivar is susceptible. There are several fungicides to choose from, select one that is effective against all three diseases. Read more about wheat fungicides at:

http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/NCERA_184_Wheat_fungicide_table_2016_V1.pdf

About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.