Recognize This Polka-Dot Succulent Pest?

A succulent pest that dots leaves with raised bumps recently showed up on this sempervivum.  "Understandable if you audibly gasp," wrote its owner, who sent photos so I could identify it and suggest treatment.

I did gasp. It made the leaves look like dotted Swiss fabric. I had no idea, so I forwarded the photos to Annie Schreck, research director at a Northern CA nursery that offers dozens of varieties of semps: Mountain Crest Gardens.

Endophyllum sempervivi

Annie identified the disease as Endophyllum sempervivi. "It's not the most aggressive spreader," she replied, "but it is European and we don't need any more of it on this side of the Atlantic. I would burn all the affected plants."

It's a fungus similar to the "rust" that affects rose bushes. The Latin name suggests it's specific to sempervivums, so initially I assumed it wouldn't affect succulents in hot, dry climates like Southern CA's. However, a credible online source that Annie mentioned---Plant Pests of Europe---shows an infested aeonium, lists echeverias as susceptible, and adds, "It can destroy the plant."

Fortunately it's not especially aggressive. But it does spread, and can even be deadly. So if it pops up, don't bother treating it with fungicide. Bag the plant and put it out with the trash.

Hail damage on Aeonium 'Lily Pad'

Speaking of polka-dots

Every spring I get emails from people anguishing over spots on their succulents. For the most part, their plants are fine. It's ususally impact damage from winter storms. Shown here is my own Aeonium 'Lily Pad' which was about as beautiful as a succulent can be...before it got battered by hail. (I didn't expect hail in March, so I neglected to move its pot a few feet, beneath eaves.)

Especially susceptible are thin-skinned, soft or juicy succulents like echeverias, Agave attenuata, and Glottiphyllum linguiforme. Don't despair: They may look awful now, but by summer, new growth will hide most of the damage.

Above: Impact damage on aeoniums caused by a strong wind blowing small rocks. Right: Same plant with new growth. From my Succulent Pests, Diseases & Problems page.

Thanks to the Polka-Dot Pest...

This new malady made me want to update my popular YouTube succulent pest video, but unfortunately I no longer have the original file. Actually, the video's fine as is, except for the music. Back then I thought a video had to have music. Maybe it won't bother you.

Even better: Bookmark this site's continually-updated Succulent Pests, Diseases and Problems page. No...even better is that you never need it!

You know, I hadn't planned to become a succulent pest expert, but evidently it goes with the territory. Actually, I don't mind ID'ing diseases and problems, especially for cherished newsletter subscribers. Btw, if you subscribe, you'll be able to send me photos.

Just know that if you're outside my region, you may have a pest I've yet to see. This polka-dot fungus popped up in Oregon. So if/when you contact me, be sure to mention where you're located (city or region), OK?