It is hard to tell without giving us your location and soil type. Your approximate location will tell us whether you are in a Mediterranean (arid) or subtropical climate. Salvias have evolved to grow in many different environments. Even better, describe the microclimate if you know what it is. This involves exposures to wind and sun, as well as soil.

The apparent catastrophic failure is probably caused by a gradual failure of the root system over time.

Foliar nematodes like Indigo Spires in particular. In most situations, their effects are negligible. When plants get stressed, they weaken plants further and accelerate their demise. Their mark is a dark patch on the leaves neatly bordered by the veins.

These pests are found on most plants. Very few nurseries control them, let alone realize they are on their stock. They were controlled collaterally in the past by the nasty, stronger pesticides that have been discontinued.

Re Salvia websites, you could take a look at mine
www.robinssalvias.com (you must have java enabled) and for more botanical information, look at Richarde Dufresne's site.

Robin.

Thanks for the reply. Let's see...I'm in the middle of South Carolina so it's hot and humid but we have had drought or borderline drought conditions for several years. This year we are about 9 inches behind in our rainfall total. Add to that the fact that my well is failing due to the dropping aquifer so that I can't water as generously as I might and you have some pretty stressful conditions.

The soil here is pure sand but I have been amending it with composted cow manure, horse manure, and "stall cleanings" - wood shavings, straw, and such. I do keep the beds heavily mulched to avoid moisture loss to some extent.

The beds where the salvia are planted are at the eastern edge of fairly thick woods (mostly oak, hickory and other hardwoods with some pine). The woods shelters the flowers from wind and from the strongest direct afternoon sun.

Your description of the nematode damage sounds right on. Is there anything I can do to save the "victim" or to protect the "survivors"? I'd really hate to lose these beautiful plants. I don't like to use chemical pesticides and such - after all, ground water will eventually find its way into my well and might, in the meantime, find its way into my dogs! Would more environmentally friendly pest control measures be of any use?

I'm sure that Rich can give you the best info, but I might add a further insight based on what you just told us, in particular the part about heavy mulch. We have HOT temps with low humidity all summer with drying winds as well, so I know drought. One mistake that people make here is to mulch so heavily that the mulch absorbs all the water and none gets into the ground, then wonder why the plants die. ANother thing I've noticed about Salvias, and it probably has to do with their wide-spreading root systems, is that spot watering doesn't work. I need to deeply water a wide area around the plants, I think so their whole root system gets watered. You might want to dig down into the surrounding soil a foot or so to make sure that the soil is damp further down.

Good points, Westelle. I do try to leave a bit of space between mulch and plant stem so that there is at least that much clear entry for water and to avoid some problems I've heard of that arise when the mulch is right on the plants (now if I could just convince my dh of the use of that!). But I have been spot watering in order to conserve as much water as possible - what I can collect in the rain barrel doesn't go far if I start flinging it willy nilly. Actually, things have been so stunted and growing so slowly in my gardens during this inhospitable weather that I'd be very surprised to find an extensive root system under ANYTHING. But I will file that information for what I hope will be more normal growth years.

I've been searching online for more about the nematode problem and, while scared witless that those may be my villains, I've come across pictures of downy mildew that look more like what is on my leaves. I didn't examine the back sides (I'll be doing that the moment I get home this evening) but I'm hoping that is what's happening...it appears it would be a lot easier to deal with. And, heaven knows, we've had the humidity to induce fungus!!

RATS!! When I got home I checked out the poor "victim" closely and I'm 99.5% sure you got it right, Rich. There was no indication of the mildew on the back of the leaves. (sigh) So I ripped out the poor thing roots, clinging soil and all and pitched it in the trash. I also picked up and off every leaf I could find that showed the dark spots. My plan is to watch the two survivors and if they get any more of the spots, well, they will have to move on to the big garden in the sky. I HATE that because they were about the nicest plants in my whole garden. ARRRRGGGG!

I also checked out the hostas - which are luckily about 20 feet away from these salvias. No sign of the nematodes. They do have some dark edges but I think it's sunburn and lack of water. It doesn't follow the veins at all.

The plants nearest to these salvias are a California poppy, lantana, and day lilies. Are any of those endangered? (Tell me no, tell me no!)

I've just uploaded an Acrobat file I prepared on foliar nematodes. It has a link in it to a University of Florida web site with more info.

Hostas are pretty resistant. The pest spreads by splashing water. Droplets that go from leaf to leaf are the vectors, as well as old foliage that carries the dormant forms of the nematode.

One advantage of buying Tony Avent's expensive plants at Plant Delights is that he controls vigorously for foliar nematodes, one of the few nurseries to do so.

Here is a link that might be useful: Foliar nematodes

How certain is it that the problem came from the nursery with the plants? They were planted in late May and have done very well til now. I realize that the nematodes can lurk about while it is dry for quite a while but would it be possible, say, for them to come in on the stall cleanout I've been getting from the stables and adding to my mulch? There is quite a lot of spoiled hay and straw and such in there. Could those plants carry the nematodes in?

In my experience, the nematodes are around most of the time but manifest when the plant is getting weak from stress. I think that the straw can be a possible but unlikely source.

I'll update the UFla link in the Acrobat file later.

Well, I'm glad to hear that. The stall stuff is my main source of amendment for this sand that we have in place of dirt. It would have really discouraged me to think I'd have to find something else!

I'm anxious to read the pdf but every time I try to access a pdf file on the internet on my computer at work it crashes my browser. And for some completely inexplicable reason, dh has eradicated Acrobat reader from our home computer! One way or the other, though, I WILL access that file. And thanks so much for your expert advice and help, Rich.

Now I'm off to browse Robin's site. Thanks for that, too.