The iris borer is the most serious insect pest. They overwinter as eggs on debris. The larvae enter the leaves when the leaves are 5 to 6 inches high and may pupate in the rhizome.
Thrips rasp the foliage causing russeting and blackening of growth.
In older clumps the tops die out and turn brown. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This information becomes public property upon publication and may be printed verbatim with credit to MSU Extension. Reprinting cannot be used to endorse or advertise a commercial product or company.