Decline of naled residue on filter paper was studied after exposure to ultra-low volume droplets in a settling chamber. Naled-treated filter papers were stored under 3 treatment scenarios: 1) in a dark environmental chamber at an average relative humidity (RH) of 46.9% and temperature of 24 degrees C, 2) in a dark environmental chamber at an average RH of 87.7% and temperature of 24 degrees C, and, 3) in direct sunlight in the field. Decline of naled followed first order kinetics in all cases; consequently, half-life of naled under each treatment was determined from the slope of each line. Half-life (+/- 1 SD) of naled was 8.17 +/- 1.24, 4.81 +/- 1.18, and 1.37 +/- 0.24 h, for treatment scenarios 1, 2, and 3, respectively. In each test, a significant (P < 0.05) decline in naled residue occurred between initial assessment and 4 h postapplication. The half-life of each treatment scenario was significantly (P < 0.05) different from that of the other 2 scenarios, indicating that both humidity and sunlight affect naled degradation rates.