Free Mossy Lure Module in the in-game shop for the current Harvest Festival Event.
The Mossy Lure Module is a PokéStop module used to attract wild Pokémon to the PokéStop's location for 30 minutes, especially Bug, Grass, and Poison types. PokéStops that have an active Mossy Lure Module placed will have green leaves floating around them. All players can utilize the effect, and any player viewing the PokéStop can see the username of whoever placed the Lure Module. Only one Lure Module can be active at a PokéStop at once, and another Lure Module cannot be placed until the previous one expires.
During the Harvest Festival Event there's an increased chance for apples to appear at PokéStops with an active Mossy Lure Module. These Apple can be an encounter with Applin/Alolan Exeggutor/Snorlax or a Sweet/Tart/Syrupy Apple used to evolve Applin.