  In this paper, we investigate the derivations in evolution algebras that are
power-associative. This problem is reduced to that of power-associative
evolution nilalgebras. We show how to calculate derivations in decomposable
algebras. This caculation shows that it is enough to describe derivations in
indecomposable evolution algebras. We first determine the derivation algebra of
$n$-dimensional indecomposable associative evolution nilalgebras with
one-dimensional annihilator. We describe the derivation algebra of
indecomposable nilalgebras, up to dimension $6$, that are associative or not.
In each cases, we give the commutator of two derivations. We also describe the
ideal of inner derivations.
