The helicopter pilot reported that the helicopter was positioned on top of a platform that was located on top of the agricultural chemical truck. And he was waiting for the ground crew to reload the helicopter. During the reload, he misinterpreted the ground crew members hand and arm signal, and initiated the takeoff. He quickly realized that the filler hose was still attached when the helicopter yawed right and simultaneously banked left. He attempted a right pedal turn to avoid tail rotor contact with the truck, and he tried to position the helicopter as far from the truck as possible. However, when the helicopter descended, the main rotor blades struck the truck and the helicopter came to rest on its left side. The helicopter sustained substantial damage to the tail rotor drive system, and the main rotor system. The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.