North American Fruit Explorers mailing list at ibiblio

["Ernest Plutko" <ernestplutko@wiktel.com>]

I never spray my fruit trees.  Because I don't have to.  Have not had
fireblight for a long time.  I see the older trees' branches and
trunks have a lot of different colored lichens on them.  Doesn't seem
to bother the trees but I'm not sure.  Trees in the woods here also
have a lot of lichens growing on them.  Do lichens hurt trees? 
Lichens do secrete acids to dissolve rocks.