Eryniasp. conidiation on larval alfalfa weevil,Hypera postica,was studied in the laboratory under constant and fluctuating saturation deficits. At optimum conditions of saturated still air (0.0 mm of Hg, 100% relative humidity [RH]), the fungus would discharge conidia for up to 50 h. Peak conidial discharge occurred ca. 3 h after exposure to saturation deficits up to 0.9 mm of Hg. Minimal conidial discharge occurred at 1.8 of mm Hg saturation deficit. Periodic intervals of high-saturation deficits had increasingly repressive effects on both conidial discharge rate and duration as saturation deficits during these intervals increased. However, the fungus had the ability to resume conidial discharge if the environment was returned to optimal and<15 h had elapsed. Wind, at 4 liters/min with an RH of 90%, had an almost identical effect on conidial discharge repression as still air at 75.6% RH.