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What is it?

A common plant disease of bearded and other rhizomous irises, caused by the bacterium, erwinia carotovora.

What does it look like?

Dieback often starts at leaf tips and progresses down to the base with leaves turning yellow and wilting. Entire leaf clusters may be found on the ground. Leaf bases and rhizomes often smell foul and are rotted.

How does it manifest?

Wounds are frequently left in plants by iris borers. The bacteria enter the plant through such wounds in leaves and rhizomes and infection develops. Plant tissue decays into a foul-smelling mass and the plant dies as the inner tissue of the rhizome rots and disintegrates. Bacteria spread by contaminated plants touching healthy ones, soil, insects, tools and other similar contact as well.

What can you do about it?

Any plants, which show signs of infection, must be discarded as there is no cure. It may be possible to save a partially infected rhizome by cutting off the diseased portion, but this may lead to additional infection of surrounding plants if you did not get it all. The safest course of action is to destroy all infected rhizomes before planting. Avoid inflicting wounds on rhizomes when digging them up. When wounds do occur, let them heal for a few days prior to planting. Plant irises in sunny, well-drained soil. The upper portion of the rhizome should be exposed slightly. In the fall, clean up all plant debris to avoid rot, and keep tight control on iris borers.