The accident occurred during an aerial application flight. The pilot made the first spray pass over the field during which he flew under a wire at the end of the field. He stated he flew under the wire to avoid spraying chemical on a neighboring field. The pilot stated that he misjudged his altitude as he entered the field for the second pass, again flying under the wire, and the top of the vertical stabilizer contacted the wire. A piece of the vertical stabilizer separated from the airplane. The rudder was bent and partially detached from the vertical stabilizer. The airplane nosed down, impacted the terrain, and slid about 200 yards prior to coming to rest. The pilot stated there were no pre-impact mechanical issues with the airplane that would have precluded normal operation.