Torpor Orb is left in the sideboard. It only stops abilities that trigger when creatures enter, and Selesnya's engine runs on landfall, which triggers when a land enters. Earthbender Ascension, Mightform Harmonizer and Mossborn Hydra all ignore it, and it would only shut off your own enters-the-battlefield creatures. Day of Black Sun is the sweeper for this matchup. At X=1 it destroys their mana creatures like Llanowar Elves and Sazh's Chocobo, and at higher X it also hits Mossborn Hydra and the four-drops like Icetill Explorer and Mightform Harmonizer, so you can reset the board before their landfall scaling snowballs. It is symmetrical, so it also destroys your own creatures with mana value X or less. Shoot the Sheriff stays in because none of their creatures are outlaws, which makes it clean removal for whatever survives. We Say Thee Nay! is the cut, as it is too slow against a deck that builds its board and mana through lands rather than spells.