Biological control agent application device

Apparatus 10 for dispensing biological control agents, such as predatory mites or insects, comprising: a hopper 20 for containing the biological control agents, and a valve wheel 50 on a valve axis A2, outside the hopper, adjacent to an orifice 29, arranged to allow the dispensation of the biological control agents. The valve axis may be parallel to a width of the orifice. The orifice may be in substantially flat base wall 28 of the hopper, which has a chamfered upper surface around he orifice. The valve wheel may have a grooved outer circumferential surface with a depth of less than 5% the radius of the wheel. There may be an agitator 60 within the hopper. The agitator may disturb the insects. There may be a lid 30 ith an overhang 34. There may be vents 27 to allow airflow in the hopper. There may be a cavity wall 26 to prevent overheating. There may be a curtain 40 coupled via a skirt 42 around the valve wheel.