Answer: In iris, iris borers work their way through the foliage and into the rhizome. Sometimes borer damage is an invitation for bacterial soft rot or other infections to also occur. Rot may also simply appear on its own. Digging the rhisomes, trimming away infected portions and removing any borers or worms, and dipping your tools and the trimmed rhizome in a bleach and water solution may help; allow to air dry and then replant. Make sure to replant so that the rhizomes are not fully covered with soil and avoid placing mulch over top of the rhizomes. Also make sure that the planting location is well drained (no excess moisture) and in full sun if possible. Iris are generally not mulched as this can provide a moist damp area where rot may occur.
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