Concentrations in air of (Z)-9-tetradecen-1-ol formate (Z-9-tdf), a mating disruptant ofHeliothis moths, were measured intermittently over a 22-day period in a corn field. The chemical was emitted from laminated plastic (Hercon®) dispensers arranged in a square grid with 10-m spacing. Measurements were made at three heights near the center of the treated plot and 1 m downwind from disruptant dispensers. Concurrent measurements were made of wind speed, air temperature, and temperature gradient.Z-9-tdf concentrations ranged from below detectable levels to 195 ng/m3 and were generally highest in the horizontal plane of the dispenser. As wind speed decreased near sunset, concentrations increased sharply, then decreased again near midnight. SinceHeliothis moths mate in the evening and early night, the concentration pattern was favorable for mating disruption. Strong temperature inversions within the crop canopy, which occurred daily before sunset, did not apparently affectZ-9-tdf concentrations. Concentrations decreased steadily on successive sampling days after application, and, by day 27, ranged from 0 to 30% of those on day 6. The data suggest that the corn plants and the soil may act as sinks for the chemical vapor at night.