|I have a large area of African Iris that are browning every week. When completely brown the leaf is easily removed and the base appears to be rotted. Any idea what may cause this problem? I have begun to assume excessive watering. Is this a possibility? Any help will be greatly appreciated. Thanks.|
|It sounds a bit like a borer infestation. The caterpillar tunnels through the leaves and downward toward the rhizome, where they begin to feed. Iris borer feeding can allow the entry of a bacterial soft rot. Rhizomes infected by soft rot are slimy, soft and foul-smelling.
There are other possible culprits, including iris diseases such as bacterial soft rot, iris scorch (probably caused by a phytoplasma), and fungal leaf spot.
I would dig up a rhizome and see if it is rotted. If it is, discard it. If it appears firm, I'd leave it for a while.