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Wilted, discolored or dying iris plants mean the iris borer has invaded your plants.
We often discover iris borer when digging and dividing our iris plants. This plump pinkish white caterpillar feeds inside the rhizome, creating an entryway for disease.
Reduce the risk by removing all the leaf litter and debris from around your iris plants each fall. This eliminates the overwintering site for the eggs laid by the adult iris borer, a day flying moth.
The borer eggs hatch in spring when the leaves are about 4 to 6” tall. The small larvae enters the leaf and begins eating its way to the rhizome. In spring watch for water streaks in iris leaves and crush the borer inside.
Remove and destroy any borers in the rhizome when digging and dividing iris. Cut away any soft areas and replant large healthy sections with one or two growing points.
A bit more information: Beneficial nematodes that parasitize the iris borer have been quite effective. Check with your local garden center, many have a special mail-order program, or check online for sources for these and other beneficial insects. Follow the directions for applying these living creatures as a soil drench in summer.
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