On April 14, 2000, approximately 0930 hours mountain daylight time, an Air Tractor AT-401, N1524H, registered to and being flown by a commercial pilot, was substantially damaged during collision with an irrigation system and terrain near Acequia, Idaho. The pilot was uninjured. No flight plan had been filed and visual meteorological conditions existed. The flight, which was an aerial application, was operated under 14CFR137, and originated from an airstrip at the accident site. According to a deputy from the Minidoka County Sheriff's Office, the pilot was taking off when the aircraft clipped a 12 foot high irrigation pivot. The aircraft then impacted terrain, sustaining right wing and empennage damage, and spilling chemicals and aviation fuel. The accident occurred approximately five miles east and three miles north of Rupert, Idaho (refer to CHART I). According to an inspector assigned to the Federal Aviation Administration's (FAA) Flight Standards District Office (FSDO) at Boise, the FAA was not immediately notified of the accident by the pilot/operator. An FAA FSDO inspector traveled to the accident site, but found that the aircraft had been removed and its whereabouts were not established. The pilot reported to the Boise FAA FSDO inspector that there was no mechanical malfunction with the aircraft at the time of the accident (refer to ATTACHMENT FAA-I). The pilot confirmed this when asked by the Safety Board investigator-in-charge during a later telephonic conversation. The pilot's local (Idaho) telephone number was called on several occasions. Each time, an answering machine message was received that identified the pilot by name as well as the operator, Mallard Flying Service. NTSB Form 6120.1/2 was mailed to the pilot's local (Idaho) address on April 19, 2000, and returned by postal authorities as undeliverable. The pilot was then contacted telephonically on May 3, 2000, and NTSB Form 6120.1/2 was transmitted to him via facsimile. As of May 25, 2000, the pilot had not responded by returning the completed report. The FAA inspector and a representative of the Idaho State Department of Agriculture both reported that the pilot had left the country and was now in Venezuela.