Cisco Storm Control – How to Filter Packets on Trunking Port

We have an unknown device causing broadcast storms on the network. I have applied storm control to ever single access port in the location, and yet the broadcast storm exists. I was wondering if I could apply Storm Control to an trunking interface to protect that switch by simply filtering excess broadcasts. So I setup storm control as follows

interface GigabitEthernet0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 storm-control broadcast level pps 1k 100
end

I then cleared the interface counters and checked the interface stats

show interface g0/1
GigabitEthernet0/1 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 0019.e781.b981 (bia 0019.e781.b981)
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, 
     reliability 255/255, txload 1/255, rxload 2/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP
  input flow-control is off, output flow-control is unsupported 
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:03, output hang never
  Last clearing of "show interface" counters 00:00:04
  Input queue: 1/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 8188000 bits/sec, 10874 packets/sec
  5 minute output rate 5000 bits/sec, 3 packets/sec
     43901 packets input, 4142320 bytes, 0 no buffer
     Received 43855 broadcasts (0 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 43763 multicast, 0 pause input
     0 input packets with dribble condition detected
     33 packets output, 4676 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

So its been 4 seconds, and I've already got 43855. That was WAY above the 1,000 packets limit I set. However, it doesn't seem to care about filtering at all and just keeps forwarding/processing the traffic.

show storm-control g0/1
Interface  Filter State   Upper        Lower        Current
---------  -------------  -----------  -----------  ----------
Gi0/1      Forwarding         1k pps      100 pps       13 pps
show storm-control g0/1
Interface  Filter State   Upper        Lower        Current
---------  -------------  -----------  -----------  ----------
Gi0/1      Forwarding         1k pps      100 pps       29 pps

Does encapsulation prevent storm control from working? Does storm control simply not work on trunking ports? I'm worried that storm control might not be in effect at all on any of the switches, despite having it enabled.