I found large grubs in bearded iris rhizomes when dividing them in late July. What are they?
Iris borers. Eggs are laid in the fall near the basal leaves and hatch in April. The larvae eat their way down, inside the leaf, until they reach the rhizomes. They then grow to 1-2 inches long with a soft, fat, pink body with a brown head. Not only can the larvae eat rhizomes, but more damaging can be the bacterial soft rot which enters the wounds. This often has a foul smelling odor. Larvae then enter the soil in late summer, pupate, fly around as moths in early fall and lay eggs for next year. Chemical controls prior to bloom may be effective, but best control is prevention. Remove any diseased foliage in the fall. Monitor in spring for small holes in the lower leaves where larvae enter and feed on their way to the rhizomes. Then if signs of fairly quick dieback and poor vigor after bloom, check rhizomes for rot and cavities where the larvae feed before entering the soil. Destroy affected rhizomes, and larvae (wire in their cavities works well), and sanitize with one part bleach to
Related Questions
- Perennials and Vines: Q– Why are my bearded iris leaves dying? (Later in month) why are some of the rhizomes mushy and smelly? A– Probably you have an infestation of iris borer. See information sheet in this section.
- I found large grubs in bearded iris rhizomes when dividing them in late July. What are they?
- When are iris rhizomes shipped, and what is the shipping fee?
