The pilot reported that the airplane’s airspeed decayed when he maneuvered to avoid some high tension power lines while conducting an agricultural application pass. He leveled the wings and applied full engine power. The pilot turned further in an effort to avoid a populated area and toward a low point in the rising terrain. The pilot added that after exiting the agricultural field, the airplane entered a valley located between rolling hills, at which time the airplane started to sink. There was a tree that was going to be a conflict so the pilot attempted to dump the chemical load. The airplane's right wing struck the tree and the airplane subsequently impacted the ground. The airplane sustained substantial damage to the right wing and fuselage. The pilot reported that there were no failures or malfunctions associated with the airplane prior to the accident.