The pilot landed the Bell 206B helicopter, and was preparing for the ninth aerial agricultural application flight of the day. Ground personnel added fuel and chemical to the helicopter, in preparation for the flight. The normal process for refueling was for one person to be in the fuel truck and one person on the ground near the helicopter. When the fuel tank was full, the person at the helicopter gives a "thumbs up" to the person in the truck, who turns off the valve. After disconnecting the hose from the helicopter, the person at the helicopter gives another "thumbs up" to the pilot, and the pilot should then verify the hose has been disconnected from the helicopter. When the helicopter requires the loading of both chemical and fuel, the number of hand signals doubles. During the accident sequence, the pilot saw the ground person give a "thumbs up" and turn away from the helicopter. He assumed the hose had been disconnected, but did not visually verify that it had. As he lifted the helicopter to a hover, it pitched down, rolled to the right, and contacted the ground, substantially damaging the fuselage and tail boom. The person on the ground reported he "mistakenly gave the all clear signal" before the hose was disconnected.