Expert: Long Island Gardener - 9/4/2009

Question
I have a dogwood tree that doesn't look very good this year...I had some firewood that had what looked like patches of a light green fungus on it and now it is on the tree. I have seen other trees with these light green patches...will they kill the tree?  Is there anything I can do for the tree to make it better and/or kill the patches?

Answer
Sounds to me like you're looking at Lichens -- exotic, harmless organisms considered hypersensitive to pollution and noxious chemicals, therefore a good test of air and environmental purity.

It takes years for Lichens to develop.  You can't plant them, and growing them at all is pretty much impossible.  Some moth larvae, possibly certain butterflies, eat them.

But this does not solve your Dogwood problem.  And that's something you have to identify before it gets worse.  Cornell University posts a Dogwood Factsheet just for you:

plantclinic.cornell.edu/treeshrub/dogwood.htm

Anything look familiar?

Think hard about how the ground around the trunk of this tree was mowed this summer.  Even one careless bang with a lawnmower can begin a whole series of problems that develop into serious damage, especially if it's done early in the season, before the bark has toughened up.  Overfertilizing, in an attempt to make the tree feel better, makes the problem(s) worse.  Then there's the possibility of weedkiller used under the tree; this is murder on Dogwoods.  Even a neighbor's use of RoundUp floating in the air to your side of the fence can do its own collateral damage before you even know it happened.

I would head over to your house to take a look, but who knows where in the world you might be writing from?  Much better to get an up close and personal diagnosis from a tree expert.  It's worth its weight in gold, and you'll know exactly what to do.  Don't put this off.  Find out what's wrong.  It's not the Lichens.  Thanks for writing,

THE LONG ISLAND GARDENER