B737 CREW BEGINS PUSHBACK WITH ONLY 1 WING DEICED.

Narrative

ON ARR INTO LAX WE CALLED FOR A SPRAY OF WATER DUE TO ANTICIPATED FROST BUILDUP ON THE WINGS AFTER FUELING. DURING PAX BOARDING; RAMP PERSONNEL CAME UP AND QUESTIONED IF WE WANTED A HOT WATER SPRAY. I TOLD THEM WE DID; AND BOARDING OF PAX AND CARGO WAS COMPLETED. CHK-IN WITH PUSHBACK CREW WAS NORMAL AND WE BEGAN THE PUSH. WE NOTICED THERE WAS ONLY WATER ON 1 SIDE OF THE RAMP; AND ASKED THE TUG DRIVER IF BOTH WINGS WERE SPRAYED. HE SAID ONLY THE L WING WAS SPRAYED. I SENT THE FO BACK TO CHK THE R WING AND HE RPTED HE COULDN'T SEE IF THERE WAS FROST BUT THE WING WAS DRY. I CALLED OPS TO CHK WITH THE DEICING CREW IF THEY DID BOTH WINGS. THEY SAID NO. I REQUESTED THEY COME OUT AND COMPLETE THE DEICING. WE SHUT DOWN #2 AND DEICING WAS COMPLETED. MY CONCERN IS WE WOULD HAVE TAKEN OFF WITH ONLY 1 WING DEICED IF WE HADN'T NOTICED THE WATER ON THE RAMP. CHANCES ARE NOTHING WOULD HAVE HAPPENED; BUT WE COULD HAVE ALSO HAD AN ASYMMETRIC SITUATION. THE DEICE CREW COULD HAVE STOPPED THE PUSHBACK UNTIL BOTH WINGS WERE COMPLETED BUT CHOSE NOT TO; CREATING A POTENTIAL SAFETY ISSUE.