The pilot reported that, after landing and during the loading for the next chemical agricultural application flight with the engine running, he exited the helicopter to speak to the owner of the property he was spraying. He could not remember if he had instructed the ground crewman to fuel the helicopter or not. Additionally, the pilot stated that, before takeoff, he failed to check the fuel level and was unaware that the ground crewman had not refueled the helicopter. After takeoff and completing only one spray pass, the engine lost power. The pilot opined that he "just ran out of fuel." Unable to make it back to the loading area, he landed in a grove of trees, which resulted in substantial damage to the fuselage. The pilot also mentioned that due to the approaching rain, he was in a hurry to get the field sprayed before it arrived. The pilot reported that there were no preimpact mechanical anomalies with the helicopter or engine that would have precluded normal operation.