This is killing a big hydrangea bush, and is now on a dahlia. White spikes with black tips.
It may be not fungus but Gall Mites.
Here is a similar appearance on the cherry leaf: Black Cherry Leaf Gall Mite (Eriophyes cerasicrumena) - JungleDragon
This could be a slime mould (Myxomycota) Diachea leucopoda -White-footed Slime or similar.
I think you nailed it. It does look like picture posted.
The internet didn’t suggest remedies for that specific thing. I found remedies for dog vomit spin slime mold* do you think it’s the same?
“Slime mold, as well as any mushrooms or toadstools, can be knocked out with baking soda, potassium bicarbonate, cornmeal, cornmeal tea, hydrogen peroxide, or commercial products like BioSafe Disease Control. Physical disturbances, such as mowing the grass or scratching the slime mold in beds, are also effective.”
If you watch the NOVA episode on Slime Mold, you will never look at that stuff the same way ever again…
Here is a short clip, but you should really watch the full episode…