do you require something that will be wax safe and not effect it or are you happy to remove any wax layer and re wax after? most will affect you wax layer though, but in theory a well protected car the sap should wash off fairly easily. Is your car waxed or sealed at the moment?
AF citrus power does a reasonable job and is wax safe but won't remove it all.
if not waxed or will be applying wax after, a tar remover will go some way to removing the majority IMO, or using a clay to remove stubborn areas. once it's all removed get it sealed or waxed and it should simply wash off during the life of the product you use.
beaten by JD, ^ as above will see you right