g'dat tonto,

most likely going to becasued by infestations of either scale insect or
mealy bugs, most of those black sooy appearances caused by the sugary sweet
excrution the bugs put out and that is what the ants use as food so you
should see ants as well.

the only othe time i have seen black soot on trees is when they are right
beside a major road and they get stained by diesel air emissions. my money's
on the bugs.

len

http://www.users.bigpond.com/gardenlen1/

snipped