I think I have Iris Borers afflicting some of my irises; unusual, since I've never had an infestation before in 15 years of tending irises, using good advice from a late neighbor who was a dedicated irisarian, a Master Gardener, and my mentor in iris matters. I've dug up the plants whose rhizomes turned a gooey yellow-orange and discarded them, but are there any other measures I should take for the remaining seemingly healthy plants: replace or sterilize the soil, use chemical or biological intervention, other? Is our warming climate perhaps the cause (I'm ignoring Republican naysayers who are clueless about emergent environmental issues)? I'll be grateful for any information. Thanks again.
Take a look at our website for information on the iris borer. We recommend cultural controls. http://extension.umd.edu/hgic/iris-borer-flowers