- Symptoms: When no pathogen can be identified as the cause of leaf spotting (see picture), the symptom may be caused by a physiological disorder or a mineral deficiency (for example, manganese deficiency).
- Development: "Splotch" of winter bread wheats and durum wheats is reported as a physiological leaf spot; the spots begin appearing during heading and increase in size and number toward the top of the plant. Spotted plants otherwise are normal. Leaf spots may also occur when cool, cloudy, and moist weather is followed by hot, sunny weather, or as a result of large fluctuations in temperature.
- Hosts/Distribution: The occurrence of physiological leaf spots is related to variety and its interaction to the environment.
- Importance: Usually not a serious problem; ongoing breeding efforts tend to eliminate genotypes prone to spotting.
