Thank you Agrigirl. I'll get some horticultural oil tomorrow. =)

Last year we noticed a bunch of what we thought were tiny black bugs all over one of the plants' leaves. I bet it was this scale stuff.

It very well might have been. They can spread from plant to plant as well (Especially in a greenhouse environment). I hope the oil works out for you. Please do post an update, I would hate for you to lose your hibiscus to these pesky critters. :-)

Here's another opinion. Doubt it's scale. (I have an idea but don' want t blurt it out without a better look-see.)

Any chance of posting an image we can enlarge? And/or close-ups?

I enlarged the images until they were pixelated.

I think it's Nectria (the small coral blobs), a weak fungal pathogen which typically attacks plant parts which have had previous damage, even though minimal. Often the underlying problem is cold damage.

If I'm correct, fungicide won't help. Instead, cut out the branch & discard, including the parts with the small black/dark blobs. Same fungus.

Thank you Jean. I'm sorry I'm just now getting back to this thread. I went into the garden center for some stuff to treat scale, and the employee asked to see a sample. She believed it to be just what you said. I have cut off hopefully all affected stems, though I suspect I will find more. The stems that had it were D.E.A.D.

Does this stuff spread? All of my hibiscus are over 10 feet tall. One is a tree form and the pride of my flower beds.

I am hoping it's not scale as that would be deadly. This black stuff was more widespread than I realized.

Jean, my most favorite tree form hibiscus has coral bumps all over it. I didn't notice them before because the black ones stood right out. If I were to cut the branches with bumps, there would be none left. Do I have another option?

Thank you in advance.

Nectria is considered a weak pathogen (disease agent). It attacks tissue previously damaged by something else, typically moderate cold damage.

You wrote:
"If I were to cut the branches with bumps, there would be none left."
It will re-grow if the roots are still alive.

You asked: "Do I have another option? "
Nope. Dead is dead. The plant is likely marginally hardy in your region. So if it's totally dead, your best option is to go shopping!

Thank you Jean, even though you didn't tell me what I wanted to hear. =P

The plants have been in the beds for 8 years, and after a very mild winter, I just cannot imagine cold damage this year ... unless this all stems from (no pun intended), an ice storm we had in early December in 2008. Ugh. Groan.

This is a helpful thread, are the black spots Necteria too? Or is it treatable? Thank you

I was horrified when suddenly I noticed a branch on my Alyogyne Huegelii...blue Hibiscus...full of black bumps!!!! Upon further examination I found it over all the branches but one young one, all the way down to the soil. They were clustered in places and more spread out in others. Some about 1/8 inch. Also, some were not totally black, but the overall look was blackish or gray. I took them all off by hand. Some were squishy and many were dry and crispy. None of my other plants have them thank goodness. I don't know if my picture is too dark, but the silhouette may be telling...Some almost look fuzzy!!? This was the worst branch.

Hi, this is what I’m seeing on my hibiscus plants. The plants are in the tropics and the branches look like they have a little roots and black stuff that almost looks like mold. Does anyone know what this is and how to treat it? Thank you.