An apparatus for destroying weed seeds for use in a combine harvester where the combine harvester comprises a separation system for separating from harvested crop at a first discharge location a first material comprising straw and at a second discharge location a second material comprising chaff and said weed seeds, the apparatus comprising: a straw chopper section comprising: a chopper housing arranged to receive from the first discharge location the first material containing straw; a chopper rotor mounted in the chopper housing having a plurality of chopping blades for chopping the straw for discharge from the chopper housing; and a spreading device for receiving the straw discharged from the chopper housing and spreading the discharged straw to rear and sides of the combine harvester; a weed seed destructor section comprising: a destructor housing (38, 39) arranged to receive from the second discharge location the second material; a rotor arrangement mounted in the destructor housing (38, 39) for rotation about an axis and including rotor surfaces (46, 46C) thereon for engaging the second material and for accelerating the feed material in a direction outwardly from the axis of the rotor; a stator arrangement mounted at a location along the direction and including a plurality of stator surfaces (48A, 48B) for engaging the weed seeds in the accelerated second material to cause a plurality of impacts with the weed seeds; and at least one a discharge mouth for discharge of the second material after the plurality of impacts; characterized in that there is provided a guide wall component movable between a first position and a second position where: in the first position the chaff and said weed seeds from the second discharge location are directed into the weed seed destructor section, while the straw from the first discharge location enters the chopper housing; and in the second position the chaff and said weed seeds from the second discharge location are directed into the chopper housing with the straw. a chopper housing arranged to receive from the first discharge location the first material containing straw; a chopper rotor mounted in the chopper housing having a plurality of chopping blades for chopping the straw for discharge from the chopper housing; and a spreading device for receiving the straw discharged from the chopper housing and spreading the discharged straw to rear and sides of the combine harvester; a weed seed destructor section comprising: a destructor housing (38, 39) arranged to receive from the second discharge location the second material; a rotor arrangement mounted in the destructor housing (38, 39) for rotation about an axis and including rotor surfaces (46, 46C) thereon for engaging the second material and for accelerating the feed material in a direction outwardly from the axis of the rotor; a stator arrangement mounted at a location along the direction and including a plurality of stator surfaces (48A, 48B) for engaging the weed seeds in the accelerated second material to cause a plurality of impacts with the weed seeds; and at least one a discharge mouth for discharge of the second material after the plurality of impacts; characterized in that there is provided a guide wall component movable between a first position and a second position where: in the first position the chaff and said weed seeds from the second discharge location are directed into the weed seed destructor section, while the straw from the first discharge location enters the chopper housing; and in the second position the chaff and said weed seeds from the second discharge location are directed into the chopper housing with the straw. a destructor housing (38, 39) arranged to receive from the second discharge location the second material; a rotor arrangement mounted in the destructor housing (38, 39) for rotation about an axis and including rotor surfaces (46, 46C) thereon for engaging the second material and for accelerating the feed material in a direction outwardly from the axis of the rotor; a stator arrangement mounted at a location along the direction and including a plurality of stator surfaces (48A, 48B) for engaging the weed seeds in the accelerated second material to cause a plurality of impacts with the weed seeds; and at least one a discharge mouth for discharge of the second material after the plurality of impacts; characterized in that there is provided a guide wall component movable between a first position and a second position where: in the first position the chaff and said weed seeds from the second discharge location are directed into the weed seed destructor section, while the straw from the first discharge location enters the chopper housing; and in the second position the chaff and said weed seeds from the second discharge location are directed into the chopper housing with the straw. in the first position the chaff and said weed seeds from the second discharge location are directed into the weed seed destructor section, while the straw from the first discharge location enters the chopper housing; and in the second position the chaff and said weed seeds from the second discharge location are directed into the chopper housing with the straw.