MECHANICAL RELEASE OF PREDACIOUS MITES FOR BIOLOGICAL PEST-CONTROL INSTRAWBERRIES

A mechanical system for field distribution of predacious mites was dev eloped for use with ground vehicles. The system released commercial fo rmulations of vermiculite carrier and Phytoseiulus persimilis. Mites w ere found to be highly mobile within the mixture and easily damaged by agitation of the vermiculite-mire mixture. The handling system consis ted of an insulated storage reservoir that kept the mixture stationary and chilled, a rotating metering plate, and an air-cleared ejection p ort. The components were mounted on a standard tractor tool bar and el ectrically powered. As the metering plate rotated, the formulation fil led cylindrical cells in the plate. As the filled cells passed an open ing on a stationary bottom plate, the cell contents fell downward whil e a brief pulse of compressed air insured that each cell was cleared. Release rate of the mites was controlled through rotational speed of t he metering plate and the size of cells on the plate. In laboratory an d field tests, the system uniformly released mobile mires with an aver age application rate error of 1.9% and an error range of -12.0% to +9. 5% for desired release rates from 32,000 to 100,000 predators/ha. A si ngle distributor mounted on a vehicle tool bar achieved productivity o f 1.9 worker-h/ha while manual release required 3.6 worker-h/ha. Machi ne productivity would be increased in direct proportion to the number of units installed on the vehicle.