The pilot had been spraying the field for about 1 hour and was on the last pass. The owner/flagger stated that he had warned the pilot (by using a two-way radio) to watch out for a standpipe and radio antenna, and the pilot acknowledged. He reported the plane was on its last pass and appeared to be high enough to clear the antenna. In the vicinity of the antenna, he observed the plane pull up steeply, roll to the right, then go down and impact the ground. An investigation revealed that the plane crashed about 125 feet beyond a fiberglass whip antenna. The antenna was about 1 inch in diameter at its base and tapered to very thin at the top, about 75 to 85 feet above ground level. About 12 feet had separated from the top of the antenna. After impacting the ground, the plane burned and was demolished. No preimpact malfunction or failures were found. The pilot died about 10 minutes after being removed from the burning plane.