What is the main conflict in Lords and Ladies: A Novel of Discworld by Terry Pratchett?

The novel's main conflict revolves around the mysterious crop circles that are appearing in Discworld and the three witches of Lancre, who must discover their origin. In the end, it is a battle between Granny Weatherwax and Diamanda, a young woman who has been dabbling in witchcraft..... Granny Weatherwax wins the battle.