Luca wrote:

I have planted a little cherry about a month ago. The tree seems
healthy, only in the last couple of days I noticed several tiny
(4-6mm) green caterpillars (if that is what they are), happily chewing
away some of the new leaves. Some even smaller black spots /dots are
always very close to the area that is being eaten.

Caterpillar poop.

These worms seem to like being snug either in a new leaf that still
has to unfold, or in between two adjacent leaves stuck together.
So far the damage to the tree is very small, however, like they say,
better safe than sorry.

Hand pluck the infested leaves off, then hose off any
caterpillars that are wandering around. On a mature tree they
don't do much damage, but it's just a baby.

Tsu

--
To doubt everything or to believe everything
are two equally convenient solutions; both
dispense with the necessity of reflection.
- Jules Henri Poincaré