Electronically controlled delivery system for beneficial insect eggs in liquid suspensions
A mechanical system was developed to meter and discharge liquid suspensions of insect eggs for release of 
biological pest control agents. The system consisted of a reservoir that was pressurized by compressed air which 
distended the bottom surface of the reservoir, agitated the suspension and forced it through a liquid supply tube which 
terminated in a tapered orifice. A pulse-width modulated valve provided intermittent flow which produced large droplets 
(ca. 2 mm diameter) of suspension. The duration of and intervals between liquid pulses, which determined application 
rate of and spacing between discharged eggs, respectively, was controlled by a microprocessor. Liquid droplets could be 
propelled outward to 3 m and at flowrates ranging from 25 to 250 mL/min per orifice. In operation, discharge distance of 
the eggs was controlled by the reservoir pressure, ranging from 10 to 50 kPa, and the flowrate was controlled by the duty 
cycle, or relative open time of the metering valve (10 to 100%). The system provided adequate agitation to discharge 
uniform suspensions of eggs in liquid carriers for 50 min and did not reduce viability of green lacewing eggs as measured 
by bioassays of larvae emergence from discharged eggs.