welcome to the forums jan ... with 18 year old plants.. not much in the way of weather is going to kill them ... especially the huge old root mass ... so though they might have taken some above ground damage.. and need some pruning after they bud out ... i suspect they will be back ... even if they die to the ground.. with no insult to the root mass.. you might be surprised how fast they can regrow ... but.. you might lose this years bloom.. give them a month or 2 longer.. to see how and where they bud out.. and then we can go from there ... [you dont mention where you are???] i suggest you take some pix then.. and start your own post.. with the pix.. and we can opine from there ... ken

The scoop is that the specific mite Phyllocoptes fructiphillus is the only proven acarid (a kind of mite in the Eriophyid group of multiple genera, each with many species) vector. There's a problem with science: it's impossible to prove a negative. Leafhoppers, for example, are proven vectors of some phytoplasmas (a disease that is not a virus and not a bacteria), and not all leafhoppers vector all viruses. And there are so many insects: a recent paper tested five different species of aphids: two transmitted a particular disease, three didn't, although it had to be worded that the three did zero successful transmissions, or some such. There is some research at Iowa State now looking at the other insects and mites and.....that are on infected multiflora to see if they are potential vectors. IMO there is a potential for root to root trasmission of RRD; it's been shown to happen with RMV. But my idea can't be tested until the disease that is RRD is catagorized as a virus or virus-like or phytoplasma. And that isn't being worked on. It is unlikely that your shears, pruners or secateurs are sharp enough to cut smoothly through a rose cane....such that the xylem and phloem elements are left open to the influx of RRD. To get RRD INTO a rose stem, it has to get into the phloem for transport within a stem/cane. That's why Epstein taught farmers to bud/graft buds of infected multiflora onto healthy bushes they wanted to be rid of. That budding required the sharpest of knives to cut both parts and then to allign the xylem and phloem elements so the graft would take. That's why we are unlikely to spread RRD within our gardens with our relatively dull cutting implements.

I bought a tropicanna last year from Lowes and through even this summer it has grown without any visable problems. I bought a black one a couple weeks ago from a local nursery and it turned out that after spending a couple weeks noticing its growth to be odd, that it was diseased. I have thrown it in the trash, luckily it grew far from my canna and my neighbors. Locally I have noticed most cannas in nurseries are diseased now that I know the traits. I have to wait to see if my other canna was contaminated by pruning off old flowers, though I don't recall having to cut any off. I didnt realize this had all gotten so serious. How is the wholesale trade keeping thier stock alive to even sell them? I would almost think it wouldnt be long before they have nothing left. I had hosta that had virus before among roses and even black eyed susan. Gardening seems too difficult these days with a global plant market distributing out of one place. There are no guards in place to protect our plant supplies and communities. I have a feeling that cold regions probably have the least diseased material since here many people don't plant them yard to yard for which I am thankful. My neighbors have huge numbers of a heritage canna that has been in their family for years so I am trying to keep my yard clean for them too. Isolation by being zone 5 is my only comfort at the moment.

" in spite of showing the most common, everyday symptom of lack of nitrogen: general yellowing. " And this may be where some of the confusion is coming in. A nitrogen deficiency is NOT characterized by a "general yellowing".....at least in an established or older plant (may show as a generalized off color in seedlings). It is the oldest (lower or inner) growth that first shows symptoms of yellowed foliage, never the new growth. That's where the plant pushes all of its nutrient reserves. If this were the issue with the plant in question - lack of adequate N - then we would see internal discoloration, not the external coloring the photos illustrate. And the new growth would not be as lush or profuse or as dense as is shown. And that is simply the way that specific nutrient deficiency works....it is not really up for debate! Yard, I am really having trouble understanding why you are not willing to accept this, including the input from two quite experienced horticulturists/plantspersons (floral and Embothrium), leaving my comments aside. It's not like yews of all types are rare commodities in either the PNW or the UK and both individuals confirm that very chartreuse, acid yellow/lime green is not an uncommon coloring for any new growth yet you seem to dismiss that as inconsequential or limited to only selected cultivars. I wish I had taken photos of the new stock at my local nursery when I was there last week, as ALL the yews were showing similarly colored new growth. It only lasts a matter of a couple of weeks before it takes on the more typical darker green color. And there is also the very real consideration that color perception is largely subjective - what seems anemic or bleached out to you looks perfectly normal to others - and that photos seldom portray color with total accuracy. I have to say that I do not see any "yellow" in the OP's photo.....just a very vibrant lime green. And the shrub appears to be extremely healthy with dense new growth and no obvious need for any fertilization at this time.