Cause The fungus, Neospermospora avenae (syn. Spermospora avenae), which infects oats and the weedy winter wild oat (Avena sterilis). It was first reported on oats in western Oregon and then Washington in the 1930s. It has occurred on the east side of Washington as well as in Idaho. It is rarely a significant problem in the Pacific Northwest but is commonly a problem on oat crops in Australia and can occur in the UK as well as other regions where oats are produced. Disease is more severe during cool (41 to 61°F), moist conditions. The fungus can be seedborne. The fungus can survive on infected oat stubble, producing spores which can be moved by wind or water and infect oat plantings. Leaf spots that develop may produce spores on the upper leaf surface, which can lead to greater disease severity on affected plants as well as spread of disease across affected plantings. Significant losses in grain yield may occur when the fungus is present during higher rainfall winter and spring seasons. This pathogen can also decrease leaf biomass.
Symptoms Disease first appears as blue-green areas on leaves that transition into pale areas smaller than 0.75 inch in length with red-brown borders and a chlorotic zone beyond the lesion borders. Spots expand on leaves, developing an irregular, elongated shape and take on a red-brown appearance due to anthocyanin pigment production. The tissue may break down in the center of lesions, leaving a hole in the affected leaf blade portion. Affected leaves typically die when disease is severe. Plants may be stunted. Disease symptoms may be confused with manganese deficiency.
Cultural control
- Avoid sowing oats in or next to a field where the disease appeared previously.
- Rotate out of oats for 2 to 3 years.
Reference Cunningham, P.C. 1990. A serious attack by Spermospora avenae on oats--a disease new to Western Europe. Plant Pathology 39(1):191-196.
Pascoe, I., and Woodcock, T. 1981. Plant pathogenic fungi from Victoria, I. Spermospora avenae on oats. APP : Australian Plant Pathology 10(3):60-61.