Abstract A series of dose–response experiments were performed at low humidity to determine if glufosinate efficacy could be increased by lengthening the drying time through the addition of humectants. Of several humectants evaluated, only 5% glycerol or 5% triethylene glycol when applied with glufosinate produced dry weight reductions and mortality similar to exposure to high humidity. 14C-glufosinate movement through isolated wild oat cuticles was greater at high humidity, poorest at low humidity, but intermediate at low humidity in the presence of 5% glycerol in the spray solution. The increases in uptake observed at high humidity and with 5% glycerol at low humidity were characterized by greater initial uptake that continued much longer than that observed at low humidity without humectant. Nomenclature: Wild oat, Avena fatua L. AVEFA.