ELECTRONICALLY CONTROLLED DELIVERY SYSTEM FOR BENEFICIAL INSECT EGGS IN LIQUID SUSPENSIONS

A mechanical system was developed to meter and discharge liquid suspen sions of insect eggs for release of biological pest control agents. Th e system consisted of a reservoir that was pressurized by compressed a ir which distended the bottom surface of the reservoir agitated the su spension and forced it through a liquid supply tube which terminated i n a tapered orifice. A pulse-width modulated valve provided intermitte nt flow which produced large droplets (ca. 2 mm diameter) of suspensio n. The duration of and intervals between liquid pulses, which determin ed application rate of and spacing between discharged eggs, respective ly, was controlled by a microprocessor. Liquid droplets could be prope lled 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 meteri ng valve (10 to 100%). The system provided adequate agitation to disch arge 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.