How do I destroy my Spawned Object, if does not toach anything?

Hi I am pretty new to Unity and have the Problem that I cant destroy my spawned object if they are not toaching my Ground. I spawning random Traps and want them be only On my Ground. Her is my SCript attached to my trap Prefab which gets Spawned:

using UnityEngine; using System.Collections;

public class Rotator : MonoBehaviour {

 // Use this for initialization
 void Start () {


         


 }
 
 // Update is called once per frame
 void Update () {
     transform.Rotate (new Vector3 ( 0, 0, 100) * Time.deltaTime);
 }

     
 //public static bool IsTouchingLayers(Collider2D other)
 void OnCollisionExit2D (Collision2D other)
 {
     if (other.gameObject.tag == "Ground")
     {
         gameObject.SetActive (false);
     }
 }

}

What am I doing wrong? (Its probably a noobie question) :)