Either way it is believed by some that a curse will take effect if it said by a parent.  For example if a parent curses a child to never be successful in their life, if the child never amounts to nothing it will be attributed to the curse.

The most dangerous curse is said to not be from a father but rather from a mother.  The mother is said to have a special bond with the child as the child is carried in the mother's womb for many months.  If the mother curses the child it is believed  that the child must have been extremely disrespectful, and will be punished. 

In fact, in no circumstance is disrespect towards a parent acceptable.  It is believed that we can pay for disrespect in this life as much as in the next.  God is said to be all seeing rewarding those who are righteous and punishing those who are not.  In the case of disrespect towards a parent the punishment is said to come sooner, and then later as well!

Directly Related:

Take a look at a Greek Folk Tale which warns you to avoid the curse of a mother:  The Good Bee.  (A tale about how a mother's curse should be feared, and her praise most wanted.) 
A Parent's curse · This is a Greeks saying associated with losing a parent's blessing what could possibly be worse!