Well, it doesn't sound too plausible to me
. Granted, the irises need "food"...whether it's derived from compost, or chemical fertilizer, but , as far as being "too hot for borers", my thinking is that it would be "too hot for the irises", as well....that is, if my definition of "hot"...…….heat caused by the rapid decomposition of organic matter (in this case, the rhizome ??) by action of a high nitrogen fertilizer....is the same as his. The "rule of thumb" about not letting the fertilizer (again, either 'chemical" or "organic") actually touch the rhizome is based on the possible damage to the rhizome, from the action of the nitrogen "burning" (is this the "too hot" ?)the rhizome, causing a wound , that allows the bacteria to enter, and cause rot.
I think I'll continue to add fertilizer....as a plant food only.....according to what a soil test indicates is needed, and rely on a combination of bed clean-up, beneficial nematodes, and insecticides, to control borer.
with Arlyn. There are still borers at times despite clean-up and insecticides. Mostly I have them on occasion near bushes or other foliage that the moths can fly from since they are low flyers. Even the search and squeeze method not using bleach water kills them. They are tenacious little buggers.
