Are there any U/W spells that give creatures -1/-1? MTG Magic the Gathering?

Well, you could toss the clic Prodigal Sorcerer alongside the Samite Archers. Lightmine Field could create a sort of demilitarized zone, practically stopping combat (unless you added something like Eldrazi Monument). And there's always Gideon Jura to combine with Lightmine or Choking Fumes to force their creatures to attack.