You can delete magento all category programatically by id or single category or specific categories.

//Delete bulk category in magento
// $catid is your category id




//Mage::register(“isSecureArea”, 1);

  for($catid=1;$catid<=34;$catid++){
      Mage::getModel("catalog/category")->load($catid)->delete(); 
 }

//For delete single category in Magento.

$category_id = 2; //category id
Mage::getModel("catalog/category")->load($category_id)->delete();  

Check Magento category exist or create category Click Here
Delete All product in magento Click Here