I have now done a close inspection of my Iris collection and identified a number of cultivars (besides my inherited NOIDs) that I am suspicious about (one in particular I intend to get tested and fully expect to test positive based on the discussion thus far). I have a lot more thoughts and concerns regarding the possible sources of the virus, but won't say further until I have evidence to indicate whether I am right or wrong.
My research has also lead me to the worrying possibility that viruses in Irises are so wide-spread that effective control may not be practical or cost-effective for people wanting to grow a variety of Irises. Until the industry changes such that large growers regularly test their plants and an effort is made to eliminate virused stock, I fear that it will be a case of needing to closely manage pests and avoiding close plantings of other susceptible genera.
We also may need to simply select for virus-tolerant or virus-resistant cultivars; ones that show no symptoms are no guarantee of no infection, unfortunately, just that the plant tolerates the infection. If my white NOID tests positive, then I can only conclude that the other three NOIDs (lavender/mauve, yellow and russet) are simply virus-tolerant, as there is no way in their long history that they weren't exposed (and some of my earlier photos suggest possible symptoms as well, whereas the white NOID is almost certainly virused and does not perform well). In that case, it will be interesting to try selfing or crossing them to try to get virus-free seedlings that are similar to the parents, as some viruses are not transferred to the seedlings.
I have this horrible suspicion that very few, if any, of my Irises are virus-free, but I'll have to get some testing done and see. Due to the cost it is impractical to test everything, so I will concentrate on a select few.
