The pilot reported that he was performing an aerial application flight to a corn field which had a tree line running west to east on the north side of the field and another tree line running north to south on the east end of the field. He was making application passes from east to west and started at the south side of the field progressing northward toward the tree line with each pass. He added that he noticed that the wind speeds increased, to about 10 to 12 mph. During the second to last spray pass, while heading west, he came over the east end tree line and descended to 5 to 10 ft above the crop. About 300 ft into the field, the airplane began to descend rapidly, and he pitched the nose of the airplane up. He added that the descent rate continued, and the airplane began to lose airspeed. The landing gear struck the corn, the airplane impacted terrain and came to rest inverted. The pilot added that he believed a combination of descending air that rolled over the north line of trees, wind shear, and the low altitude flying, and reduced margin of error for the proper application of pesticide caused the accident. The airplane sustained substantial damage to the empennage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. A weather station, located about 3 miles to the northeast of the accident site, about the time of the accident, reported temperature 85.3°F, dew point 68.3°F, and wind from 293° at 6 mph, gusting to 8 mph.