There are not many Wizard spells that do ability damage, and off the top of my head, there are no good ones (the only one that comes to mind is chill touch, which is an awful spell for a non melee wizard).
However, fear not, for a debuffing Wizard has lots of other options. Remember, debuffing doesn't have to be ability or level damage. Any spell that succeeds in making your enemy weaker is a debuff.
If you want to make a debuffing wizard, check out color spray at level 1, when you get second level spells, consider either Blindness/deafness or Glitterdust (but not both - they are redundant), when you get level 3 spells, Slow is a great mass debuff, though I have a soft spot for Ray of exhaustion (for single opponents), as it has a partial effect on those who save. When level 4 spells become available, then Enervation is a nasty debuff with no save, though against mass enemies, look at confusion or fear.