I live in a drier environment than you, Mary Ann, so take this for what it's worth, but my advice would be to do nothing except maybe scoop out the soft parts. The barrage of chemicals approach is rarely effective with fungi. They are amazingly resilient organisms. The
spores of fungi are ubiquitous and all but impervious to environmental factors. They survived in the blast zones of nuclear weapon test sites, they aren't going to be deterred by anything we can throw at them.
The other thing at people often fail to consider is that most perennial plants, including irises, develop symbiotic relationships with mycorrhizal fungi that actually live in the plants' roots. Mycorrhizae greatly enhance a plant's ability to take up water and nutrients from the soil. Fungicides probably aren't any better at actually killing mycorrhizae than other fungi, but they do drive mycorrhizae out of plants' roots, making for weaker and less healthy plants that are then more vulnerable to pathogens. Consequently, relentless spraying of fungicides probably does more harm than good.
I had outbreaks of Botrytis last year and this year. It cost me quite a bit of bloom last year, and probably will again this year, on newly planted varieties. But it's only actually killed two plants, Boy Genius and Vow of Silence. Both were bonuses, which made it easier to take I suppose, but I just shrugged, figured they weren't tough enough to live here, and started thinking about what to put in their spots.
Looking back, I'm pretty sure Botrytis has been present in my iris beds from the start, it just didn't do enough damage to really catch my attention. I think the weather the past couple of winters was really favorable for its growth. When we get back to more normal winters (if we do), I expect it will fade back to insignificance. If not, there are plenty of iris varieties that seem to be able to shrug it off, I'll just limit myself to growing those.
