Key Features
- Brown spots on leaves
- Blighted brown areas on leaves
- Fewer or smaller blooms
Symptoms
Iris leaf spot symptoms first appear as small brown spots surrounded by water-soaked margins. Spots enlarge slowly until the iris blooms, then the spots enlarge rapidly. Multiple spots may coalesce on the leaf tissue causing premature death of the leaves. Severe outbreaks of this disease may cause a reduction in bloom, and plants with severe repeat infections may eventually weaken and die. See Leaf Spot-Mycosphaerella, too.
Biology
The fungus overwinters in the previous year's leaves. Therefore, good sanitation in the fall of all debris is important to prevent the disease the following year.
Management Recommendations
Remove and destroy spotted or dead plant material, cutting out diseased foliage, especially in the fall, to reduce the number of spores available for infection the following spring. Plant iris in full sun. Fungicide application may be necessary during wet years. Fungicides may also be applied after infected portions of the leaves are cut off to prevent further infections.
Effective Pesticides
Active Ingredients include: Chlorothalonil, Myclobutanil, Thiophanate-methyl
Resources
- Not satisfied with ID? Contact the Purdue Plant and Pest Diagnostic Lab
- Sign Up for the Purdue Landscape Report
