black soot on lemon leaves
There is a mysterious thick, black soot covering the leaves of my Meyer
lemon tree. The tree is around 15 feet from the trunks of my neighbor's
redwood tree. It's in our backyard which is quite far from the street. In
other words, I can't figure out where this soot may be coming from except
from the redwood debris.
We've had intense rains here in the SF Bay Area and even these don't clean
the stuff off. Of course some of the tree is under the thick branches of
the redwood but much of it isn't. Well-some of them look like they're not
under branches because the branches they're under are from 20 to at least
100 feet high.
Any ideas about what this nasty stuff could be and what can be done about
it (other than hand cleaning each leaf every week or so!)?