Hi Lorenzo,
Do you know what variety of apple this is?* In looking at your picture I'm thinking the problem could be one of several different diseases.* This site has some good pics and info.
http://www.caf.wvu.edu/kearneysville/wvufarm8.html
I'm thinking maybe nectrotic leaf blotch aka golden delicious necrotic leaf blotch.
http://www.caf.wvu.edu/kearneysville...ages/fig72.jpg
Here's the overall symptoms on a Goldend Delicious tree.
http://www.caf.wvu.edu/kearneysville...ages/fig73.jpg
Here's the info on this disease.
http://www.caf.wvu.edu/kearneysville...ons/gdnlb.html
Here's the list of symptoms for apple.
http://www.caf.wvu.edu/kearneysville/wvufarm8.html
Any of that look like what you see?
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.