Minecraft wiki entry for Cocoa_bean_farming, associated text: Cocoa beans will break if the bean itself is hit by the player or a piston, if the jungle wood itself is pushed by a piston, if water occupies the same space as the growing bean, or if the jungle wood block is destroyed. All automated harvesting relies on these methods. Theoretically, TNT would also remove the beans but would be costly to implement and difficult to replant.