Septoria Tritici Blotch

• Zymoseptoria tritici is the name of the anamorph of the causative pathogen and Mycosphaerella graminicola is the name of the teleomorph.
• This pathogen was discovered in 1842 and is now considered the 2nd ranking global pathogen of wheat.

Zymoseptoria tritici on wheat leaves, note how leaf veins delimit the lesions and pycnidia is visible in lesions.

• The primary inoculum is spread from infected crop residues via airborne spores and raindrop splash.
• Beginning symptoms start right after seed emergence as chlorotic spots develop.
• These irregular or elliptical lesions become tan and develop dark fruiting bodies, pycnidia, within lesions.
• Pycnidia will produce whitish ooze as spores disperse. Lesions are delimited by leaf veins, developing in substomatal cavities, which cause them to be evenly spaced.
• Secondary inoculum is spread through direct contact with infected plants and wind dispersal of spores.

Ascospores of Zymoseptoria tritici emerging from a pseudothecia (dark colored overwintering structure). Photo courtesy of Mary Burrows, Montana State University, Bugwood.org.

Asexual spores of Zymoseptoria tritici. Photo courtesy of Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org..

• This pathogen persists in the system from infected seed, residues, and cereal crops that are overwintering.
• Disease is polycyclic, re-infecting as long as the conditions are cool and wet, which is favorable for this pathogen.

• Resistant cultivars are economical but their effectiveness varies greatly from one region to the next.
• Zymoseptoria tritici overwinters in crop debris, so practices that reduce the amount of crop residue on the surface such as tillage, late planting, and crop rotation, will decrease the amount of primary inoculum.
• Foliar sprays are available, but this pathogen quickly develops resistance to fungicides.

• Ponomarenko, A., Goodwin, S. B., & Kema, G. H. 2011. Zymoseptoria tritici blotch (STB) of wheat. Retrieved from the American Phytopathological Society.
• Salgado, J. D., & Paul, P. A. 2016. Leaf Blotch Diseases of Wheat—Zymoseptoria tritici Blotch, Stagonospora nodorum Blotch and Tan Spot. Retrieved from Ohioline.