Unidentified pest is attacking all my succulents

In the last two months I've gotten really interested in succulents (with only minimal gardening experience before this) -- I only kind of know what I'm doing. My plants were flourishing here in the San Francisco Bay area, but a week or two ago I noticed some little white/beige spots on my Echeveria Mexican Snowball. They seemed harmless at first, but after a while they expanded into little cancerous-looking marks -- at which point I removed it from the window box in hopes of saving the other plants.

It was too late, though, and over the next several days I noticed it on some echeverias, crassula ovatas, graptoverias, and I think also my crown of thorns plant. I'm trying to figure out how to stop whatever these are, but I can't figure it out.

I don't know anybody who knows anything about garden pests, so I researched online and decided it was probably scale. An employee at my nearby nursery said he thought it was aphid damage, but I can't find any bugs anywhere even though new marks have continued to appear.

So I tried a bunch of things: I got some Bayer "insect protection" spikes and poked them under my plants. I also got some tomato and vegetable insect killer with 0.012 pyrethrin and sprayed it on as thoroughly as possible. (I did it a bit too early on a sunny day and my plants got a little red on the edges, but nothing too serious.) A few days later, with the marks appearing on even more plants, I got some Year-Round spray oil and sprayed that on every surface I could. It must have taken me twelve minutes to feel like I got full coverage.

In related news, I used to see some miscellaneous brownish bugs hopping/flying around on the soil, but I haven't seen any since I initially sprayed the insect killer -- about nine days ago. Despite that, more marks have appeared on more plants -- the echeveria harmsii went from perfect condition to all spotty between last night and this morning.

Does anybody have any ideas what this could be? I would be incredibly appreciative! Sorry for such a long post -- I just wanted to include as much information as might be helpful. The photo of the Mexican Snowball echeveria is probably the best one for seeing the mystery pest.

Thank you!

PS - I found a couple of slugs last month, so I spread some Sluggo around. I have since found two dead slugs, so I don't really think they're likely to be causing this damage.

Wow...what a bummer. I can not tell you exactly what is harming your plants, but I can give you info that may help you determine what is happening. I am also fairly new to growing succulents so my experience is limited. It sounds as though you are trying to cover all bases on getting rid of the problem.It is possible that the damage is being done by "fly through" insects...those that feed and move on, or possibly insect larva in the soil. I think these links cover all the bases from bug to environment to disease...

http://www.youtube.com/watch?v=onqH_yYV2I4

http://www.succulentguide.com/cactipests/

http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/mealybugs/insect-pests-of-cacti-and-succulents.aspx

http://www.botanicalgardening.com/candspests.html

http://www.cssainc.org/index.php?Itemid=212&id=251&option=com_content&task=view

Thanks very much! Sadly, nothing on those sources looks like what I've got. The Succulent Guide link looked really useful, but it was hard to use for identification with so many broken images. This morning I noticed no new damage, at least, and it's the first time in several days that I've been able to say that. Maybe the various chemicals I applied made a difference. If anybody recognizes the damage from the photos, though, I'd sure feel a lot better if I knew what the actual problem was so I could prevent it in the future.

I am so sorry the info wasn't helpful to you. Good that you saw no further damage.

The last picture does look like something is eating the leaf, eating small holes, then the leaf turns white where the damage happened.

Try trapping some bugs.
Many pests live in the soil, or under the pots (if the plants are in containers) during the day.
You can trap them by loosely rolling some newspaper and setting the roll near the plants. The bugs may come out to feed overnight, then go hide in the rolled paper in the morning. Open the roll of paper into a white bucket and see if you have trapped anything.

Also, check the plants at night with a flashlight.

If you have no pets that might eat it, you can use other baits with different attractants and different pesticides to try to kill pests other than snails and slugs.

The last picture is the only one I looked at, and the spots on that plant remind me of 'shot hole fungus'. My cacti --growing in heavy clay soil-- have it, and it starts out eating the surface of an area away, but eventually eats all the way through, and the plant seals the sides of the hole.

From what I understand, it is caused by either over-watering &/or poor draining soil. It is a fungus, and its spores are air-born. They can also get splashed on other plants from infected leaves or infected ground, whilst watering.

I've never tried to figure out how to eradicate it, so can't help you with that, other than to warn you to stay away from chemicals. They are *very dangerous* when used alone (no matter what the labels say), however, they become a *thousand times more* toxic when combined together . . . That is *POISON* with a *capital* 'P'!!!

You might need to start over with new plants, new soil, and new pots, unless you can find a way to sterilize them all. The pots & soil can be sterilized, but I doubt that the plants can be. And, baking the soil the only way I've heard of to sterilize it) is *horribly* smelly, I'm told.

That is . . . if that is what the problem is.