NPIPM:Septoria/Stagnospora blotch
Authors: Byamukama, E., Ali, S.
Causal Organism
Septoria/Stagonospora nodorum blotch is caused by Parastagonospora nodorum (previously named Septoria nodorum, Stagonospora nodorum).
Symptoms and Signs
Small lesions begin on the lower leaves as irregular water soaked patches that will eventually develop into lens-shaped lesions with dark brown borders. As the lesions expand, the centers will become lighter, necrotic, and take on the shape of a lens. Mature lesions have small black and brown flecks that can be visible under magnifying glass or hand lens. The fungus can also infect the wheat head causing purple-brown blotches on the glumes starting at the glume tip.
Disease Impacts
Severe infection can cause significant grain loss, light weight grain, and shriveling of grain, which results in a negative effect on yield and test weights. Planting infected seed can result in seedling blight and a low germination rate.
Life Cycle and Epidemiology
This pathogen overwinters on volunteer plants and on wheat stubble from the previous season. Seed can also be the source of inoculum. Wet (12-18 hours of continuous free moisture) and warm weather are optimal for infection. Optimal temperatures range from 68°F to 81°F. For this reason, this disease develops at a higher rate around the time of heading.
Management Approaches
Rotating crops with non-host crops prevents inoculum build up. Plant treated clean and certified seed to avoid seed-borne inoculum. Nitrogen based fertilizers, when applied in excess, will promote fast flush growth which is conducive for fungal growth. Foliar fungicides timed at flag leaf emergence are effective against Septoria/Stagonospora nodorum blotch.
Other Online Resources
http://ohioline.osu.edu/factsheet/plpath-cer-07
