Iris Basics: Unwanted Guests
Irises do occasionally draw pests and diseases. Here are links to a few articles that might help you;
The American Iris Society website has an excellent article offering basic information on iris pests and diseases. Use this as a starting point. The photos are excellent.
A powerful new weapon against iris borer has emerged: a tiny nematode that can be sprayed on a garden. Find information and sources in this article.
For information on the iris borer life cycle and several other treatment methods, including spring burning of the iris leaves, visit this link.