Moldy stuff on Trichocereus spines?

[nitrogen]

Anybody know what this is or what its from? - my longer spined bridgesii seem to get it...

[mutant]

does it get 'black rot' too?

[AndyAmine.]

There is no need for x2 of the same thread, this one should really be deleted/merged.

FYI after having another loook at my cacti it seems to me as though it is caused my morning dew/mumidity more than anything else.

That is unless the spines exude some kind of mositure on their own, which I swear they do at times but its probabaly just left over dew or something.