Implements hook_menu_local_tasks_alter().
Remove the 'Add Forum' and 'Add container' local tasks on the delete form.
function forum_menu_local_tasks_alter(&$data, $router_item, $root_path) {
if ($root_path == 'admin/structure/forum' && !empty($router_item['map'][3]) && $router_item['map'][3] == 'delete') {
$data = array();
}
}