Iris Diseases

Informational table showing disease name, symptoms, pathogen/cause, and management of Iris diseases.
Iris Diseases - Articles


Bacterial Leaf BlightFaint water soaked spots on leaves enlarge along the leaf when weather is wet but cease activity when it is dry.Xanthomonas campestris pv. tardicrescensRemove infected leaves. Avoid overhead irrigation.
Botrytis Rhizome rotFew leave emerge in the spring. Leaves are yellowed, turn brown, and die. Gray masses of fungal spores form on infected leaf tissue. Rhizomes have a dry, mealy rot. Large, shiny, black, granule-like structures (sclerotia) form on the surface of infected rhizomes.Botrytis convolutaDo not plant infected rhizomes. Destroy infected plants.
Crown RotLeaves die slowly from the tips. White fungal threads can be found at the leaf bases. Tan, spherical structures (sclerotia) form between rotting leaves.Corticium rolfsiiDiscard infected bulbs.
Ink Spot (Bulbous Iris)Tiny spots and streaks on leaves enlarge and become dark reddish brown. Spots may become gray in the center. During wet weather, dark masses of spores form in the spots. The plants yellow and die prematurely. Heavily infected bulbs may rot before flowering occurs.Drechslera iridisDestroy leaf debris. Remove and destroy infected bulbs. Apply a fungicide to protect plants.
Leaf SpotSmall brown spots with water soaked margins turn yellow, ehlarge and develop reddish-brown borders. Leaves die. Dark fungal spores can be seen within the spots with a magnifying glassMycosphaerella macrospora (Didymellina)Remove and destroy infected leaves and leaf debris. Apply a fungicide to protect plants.
NematodesBlack streaks develop along the veins of outer leaves of bulbs. The basal plate is gray and separated fro the outer scales by a dark sunken groove.Ditylenchus destructorDestroy infected bulbs. Plant in nematode-free soil
Soft RotLeaves collapse suddenly or die gradually from the tips. The base of infected leaves and infected rhizomes have a foul smelling soft rot.Erwinia carotovora pv. carotovoraDestroy infected rhozomes. Control iris borers which often cause the injury where the bacteria initially gain entry.
VirusMild mosaic on flower stalks and spathe (mild mosaic virus). Yellow green stippling and stunting (severe mosaic virus). Flower color breaking and puckering can occur.Iris mild mosaic, iris severe mosaic, cucumber mosaic (all aphid transmitted), broad bean wilt, tobacco ringspot, tobacco rattle, bean yellow mosaic, narcissus latent virus, bearded iris mosaic, beardless iris mosaic.Most iris cultivars tolerate viruses. Destroy severely affected plants.

Leaf spot symptoms.

Prepared by Gary W. Moorman, Professor of Plant Pathology