Iris Borer
Iris Borer
The insect overwinters on old leaves or debris as eggs. The eggs hatch in the spring when the leaves are about 6 inches tall. The young larvae burrow into the leaves. The and eventually bores into the rhizomes. The insect pupates in the soil or the rhizomes and the adult moth emerges in late summer to lay eggs.
One of the most visible symptoms is poor growth. However the insect often introduces bacterial soft rot which will cause a foul smelling rot.