I know the Patronus Charm is the only effective spell against Dementors - but does any other spell have an effect on a Dementor?
E.g. in The Order of the Phoenix Mundungus Fletcher was supposed to look for Harry Potter in Little Whinging. If he had not left he would have had to help Potter with the Dementors. But I really doubt that he was able to perform the Patronus Charm so he would have tried any other spell on the Dementors.
edit: What are the other ways of tackling dementors? and How can Voldemort counter a Dementor? are related to this question but both do not answer how especially spells could have affected Dementors. Mundungus Fletcher couldn't have helped Harry Potter just by controlling his feelings, becoming an Animagus or getting a ghost, he would have tried something like the Stunning Spell - maybe without any success.