Scenario: Black Mercy Plants!

So here's the scenario. Mongul's son has infected a small Ohio town with the Black Mercy plants. Superman comes in to save the day with Linda Danvers (who I'm pretending hasn't gone to hell). Logically, how would the two defeat Mongul and destroy the Black Mercy plants if Mongul also has a Sinestro Ring?

They would bring the recently unshrunk Kandorians with them.