Need help identifying white spots on shingle siding!

We were doing a light house wash and this home is freckled with white spots. I did a finger test and it was kinda chalky in spots and hard to pick at in other spots. It didn’t budge with a water wash and and a brush. It fades when wet but just drys back to the same as it was.

The home-owner only wanted Eco-Safe chems so we tried diluted (10-1) Cedar Wash but that didn’t remove the spots either. However, we didn’t let it dwell at all. Just an application and immediate rinse.

Most of the home’s finish is in relatively good shape.

Could it be efflorescence? I’ve seen that it can be on wood but should it be on wood that still has stain or oil that’s in good shape? Or what else could it be?

Here’s a few pics to check out. Tell me what you think.

  1. never let a customer dictate what you use
  2. since you did, now your stick with a job where you probably won’t get paid

3). Looks like paint splatter, bird crap, …I don’t do wood though so it’s probably neither of those


I told her in the beginning I didn’t know what it was and couldn’t guarantee it would come off with the treatment she was asking for. I would do a wash and see what happens. She was still happy and paid. Just wanted to see if any wood guys recognize this stuff. I don’t think its from birds, it’s all around the house. Seems like maybe a moisture problem and something’s growing. Lots of gardens on a river. We were going after dust and cob webs and if that came off too, then great. But it didnt. Hoping someone’s seen it before.


Any chance they ever sprayed for bugs or other pests?


Got a more distant pic so we can see what rest of house looks like. Looks like paint splatter from pic but if no light colored paint anywhere, don’t have a clue. Never anything like it before that wasn’t splatter.

I’m sure they have sprayed for bugs, they have alot of vegetation around the house.

Here’s a farther out pic. The spots are under the light in this one. No white paint near it, or anywhere really. All dark colored paint. Just white freckles everywhere.

Are most the spots on the house near lights?

No, the spots are sporatic around the house. Some high, some low. Some on 2and story. Doesn’t seem to be a pattern. I’ll take more pics this Thursday when I go back to retrieve my sign. I’ll keep you posted.

If it was just around lights I was going to say could be bug or spider droppings

What ingredients were in the Cedar Wash that you used?

I wonder if the specks are just some form of fungus. I would do a test spot with some sodium percarbonate, light agitation, followed by about an 800 psi rinse.

Yeah, that came to mind too.

The cedar wash is peroxide based. Diluted it way down so as not to remove the stain.

I do have F10. I’ll try that.

More pics to come later this week

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OK, here’s some more pics to add to the pile in case anyone who’s seen this before stumbles across this post. Not sure if they’ll be helpful or not. Might zoom in on some. There’s one pic with the gutter in it, you can tell how high the spots are.

Note: The homeowner says she doesn’t spay for bugs. They are way too organic for that.

Is white mold an option? The back yard butts up to a river. Moisture problem?

Anyway, Thanks for the ideas and taking a look.

I have these same issues with my cedar siding and am wondering how to remove these stubborn white stains. They weren’t there when we bought the house last January!

I never did figure out what it was or how to remove it. Sorry, Wish I could help.

Maybe woolly aphids?

Looks similar to what I have all over outside AND inside. Never knew this thing existed until a few days ago.

I’ve used rubbing alcohol, fire and neem oil to kill them and they all do the job. But haven’t made a dent.

Anyone out there know alot about these pests? There’s not much info out there about the woolly and I can’t find answers to my questions.

Every page says they feed on sap from trees. Not much about other plants but seems they do. But how are they thriving and surviving inside the house when there are no plants?