According to the pilot, he was on his sixth aerial application pass of the third field for the day. He reported that during that pass, the airplane's tail struck "unseen powerlines". He recalled that the powerline wires crossed the field at an angle, and that the powerline poles were hidden by the trees on both sides of the field. The pilot flew to a nearby airport, and landed without further incident. The vertical stabilizer and the rudder sustained substantial damage. In accordance with 14 CFR Part 137, Section 19, (e)(1)(i)(vi) (a) General. An applicant for a private agricultural aircraft operator certificate is entitled to that certificate if he shows that he meets the requirements of paragraphs (b), (d), and (e) of this section. An applicant for a commercial agricultural aircraft operator certificate is entitled to that certificate if he shows that he meets the requirements of paragraphs (c), (d), and (e) of this section. The agricultural aircraft operator is entitled to a commercial agricultural aircraft operator certificate if the operator can show that the knowledge and skills required by the Commercial Operator per paragraph (e) are complied with, which include: (i) Steps to be taken before starting operations, including survey of the area to be worked. (vi) Safe flight and application procedures. During an interview with the operator, the investigator-in-charge asked if documented training was provided to pilots regarding the location of wire hazards for the area of operation? The operator said, no. At the request of the investigator-in-charge, the operator agreed to provide documented, local area powerline wire and obstacle avoidance training to the pilots that are performing aerial application operations for the organization. The operator has completed the recommended training. The pilot reported that there were no mechanical failures or anomalies with the airframe or engine prior to the wire strike, that would have prevented normal operation.