This morning I went into my semp garden for my usual fix of sunshine-on-the-sempervivums. I looked down upon my Jovibarba 'Blaze' and decided the situation had gone on long enough. There were three individual plants that had come with an order from Young's. One was a largish rosette looking quite spry. Another was a a smaller rosette divided in two, also looking quite happy. I could feel that both of them were quite firmly rooted. Between them, however, was a third plant with three rosettes dividing it. It was obviously struggling. The leaves were small and leathery, and there were multiple dried, brown leaves around the perimeter. It seemed to actually be shrinking slightly from week to week. It also did not feel solidly anchored. Pulling it from the ground revealed the obvious, lack of root development. But why? Then I noticed small white creature moving quickly around the old dead root stump. Then another. I immediately recognized them as the dreaded Garden Symphylan, an agricultural pest that wreaks havoc along the west coast of North America and is impervious to any controls available to the home gardener. I believe this is the biggest reason the farmers around me fumigate their soil on a regular basis.
Anyway, this is the second plant I've found with these symptoms although previously I had not suspected Symphylans. But it does make perfect sense. In both cases I found a few brand new tap roots although there had been time for extensive root growth. Those roots I believe would be soon discovered and attacked. The Symphylan loves to eat tender new root tips. As the semp desperately tries to grow new roots to establish itself, those roots are nibbled right back. The semp keeps trying and trying, losing vigor with each lost root. The plant ends up looking very much like a plant that has been left on a table top, unable to root.
Symphylans are a regular pest in my vegetable garden, especially with squashes. I hadn't thought Symphylans to be a Sempervivum pest but I now know otherwise. My garden is particularly vulnerable since it is at least slightly moist throughout the year. The Symphylan requires moist surroundings and soil that dries out completely from time to time will limit their numbers. In no case have I found plague-like numbers, just nuisance levels.
The good news is that I don't think that semps with healthy root systems are much affected. However, rootless transplants may have trouble establishing new roots if Symphylans happen to find them. Going forward I don't think I have much to worry about except an occasional victim. Although I will take some special care for any rootless specimens received from Europe.

Wow, Tim this is very interesting. Can you get us a photo of what they look like? Even if it is from your veggie garden.

Yikes. Never seen or heard of them before but reading about them, they sound even worse than gophers. At least one can lay down hardware cloth to keep the gophers out.

Actually, even when present, they are very hard to find. They are tiny, fast-moving, and detest the light of day. To get a photo I'd surely have to kill it and in doing so it would be disfigured and my camera couldn't even get a decent picture.

Here is what Google images returns: https://www.google.com/search?...

In reality they are smaller than a tiny ant, these pictures make them look quite larger. You have almost doubtless run across them from time to time. If you've ever been digging, even in potting soil, and noticed a tiny white arthropod scampering for cover, that's a Symph. If they weren't snow white, you might never even be able to spot them. If you do see one you would just think that it is a leaf-litter creature subsisting on organic matter in the soil. And for the most part that's true, but they also have an appetite for tender, juicy root hairs and they can do serious damage. Generally to tender, domesticated plants like vegetables. They have been nicknamed the Achilles Heel of organic gardening.

I'm suspicious of this particular semp pictured below. These two rosettes were planted together at the same time. The one on the left is solidly rooted and looks happy. The one on the right though feels a bit loose and clearly has some issues. I'm certain that its root development is not what it ought to be. Or course, I can't say that Symphs are to blame but it surely wouldn't surprise me. I know this plant had some roots when I planted it and I suspect they are being attacked by a couple of Symphs, maybe just one. They are highly active and mobile in the soil and will traverse a small root system looking for tender tips to taste. I think this particular one has enough roots left to barely survive, for the time being at least. The four chicks on this plant have rooted themselves and appear more solid than their parent. I'm going to leave this alone until the chicks are a little more established and then lift the parent rosette and see what I can see. I don't like mysteries.

Hopefully with your diligent watching the EU semps can prosper! Good Luck and thanks for sharing this with us, Tim.

Oh no, sorry to hear that Tim. Sounds like you've done plenty of research though and hopefully you won't have many problems with them. It's always something, isn't it?

Oh Tim, I'm so sorry, what a bummer. I hope those horrible, little devils' never show up here! I have enough to worry about. We get the most awful, humid heat. Not every semp cultivar can handle it. Even in the shade it's terrible. Yep, it's always somethin'!

It's not all as bad as I may have let on. It's just another part of nature that will take its toll from time to time. I doubt I will ever completely lose a cultivar because of it. Now that I think of it (too late)... my 'Blaze' rosette could easily have been rinsed free of the scourge and replanted. Since it was clearly able to grow new roots if they weren't being chewed off.
This is a West coast pest. See? It's not all roses in the Willamette Valley... just mostly.

Just mostly. Who are you kidding? You PNW folks have it made over there. Believe me, if we could have moved my studio and Bill's shop to your side if the continent, We would have! Moving all the heavy equipment and large kilns would have cost at least a trillion dollars.
You guys have a longer growing season too, that alone is very appealing! Gotta love the PNW!

I have to agree with you Terri, to me the PNW is paradise on earth.