Yes, it looks so. The genus has changed, it is now Sclerencoelia fascicularis, because Encoelia furfuracea is very distantly related, and this one belongs in Sclerotiniaceae.

There is, however, a North American species on Populus, S. pruinosa. We know it, e.g., from a recent collection by Joey Tanney from Quebec, on Populus grandidentata or P. tremuloides.

It has abundant crystals, probably therefore the name, but crystals occur also in S. fascicularis. I am not sure about a certain record of that species in America.

Zotto

Thank you, Zotto.  The "abundant crystals" of S. pruinosa are the fine hairs on the outside of the fruiting body, or something else?

Nono, I mean octaedric crystals. maybe I see very small ones on your excipulum, but when you look at Tanney's photos they are striking (folder Sclerencoelia in Sclerotiniaceae on my homepage).

Last weekend I collected what is likely S. fascicularis on a dead Populus tremuloides branch still attached to a living tree. The branch was covered in S. fascicularis apothecia as well as Valsa sordida pycnidia; it was quite impressive, at least until my dog destroyed the specimen that I brought back with me (at least she waited until I had taken photos).

Yesterday I took my dog for a walk and found a nice specimen of S. pruinosa on the bark of a dead Populus tremuloides tree. Macroscopically, the apothecia are quite smaller than S. fascicularis, more densely coated in crystals (it looks like they are sprinkled with salt), and when dry they are inrolled and appear triangular or clam-like. From my few observations of these species, it seems that S. fascicularis is on dead branches and S. pruinosa on the bark of dead trees... maybe S. fascicularis is a branch endophyte that sporulates after branch death while S. pruinosa causes sooty bark canker? Sclerencoelia fascicularis apothecia are also erumpent from the branch and appear in clusters (fascicular) whereas S. pruinosa apothecia are gregarious but not in such distinct clusters.

I will moisten my S. pruinosa specimen, which is out of the dog's reach, and try to take better photos tomorrow.

Hi Joey!
I fully agree with your hypothesis, I think it is also what is known about S. pruinosa being the caus of a canker. And with "bark" you mean trunk bark, because all Sclerencoelia species grow on bark. 

Your last pic refers to S. pruinosa?
Zotto

Yes the bark on the trunk of the tree, not the branches. The last picture is of S. pruinosa - I just took some rather poor low-res pictures now, but you can see the crystals and some hydrated apothecia.

I will have to keep an eye out for sooty bark canker symptoms on living trees, because I have only noticed the apothecia on dead trees with the bark already sloughing off. In my area (eastern Canada), Entoleuca mammata is the major canker-causing fungus on poplar, whereas sooty bark canker is apparently the most important poplar canker in western Canada.

O.k., this is impressive!