BIOLOGICAL-CONTROL OF FUNGUS GNATS, BRADYSIA SPP (DIPTERA, SCIARIDAE), AND WESTERN FLOWER THRIPS, FRANKLINIELLA-OCCIDENTALIS (PERGANDE) (THYSANOPTERA, THRIPIDAE), IN GREENHOUSES USING A SOIL-DWELLING PREDATORY MITE, GEOLAELAPS SP NR ACULEIFER (CANESTRINI) (ACARI, LAELAPIDAE)

A soil-dwelling predatory mite, Geolaelaps sp. nr. aculeifer (Canestrini), introduced inundatively at a rate of 6000 mites per plant to the sawdust substrate of hydroponically grown, greenhouse cucumbers significantly reduced numbers of fungus gnat, Bradysia spp., larvae and adults over a 10-week period. Inundative introductions of 1600 mites per plant reduced emergence of western flower thrips, Frankliniella occidentalis (Per-gande), adults to about 30% of that in the controls over a 40-day trial. An inoculative introduction of 125 mites per plant to cucumber plants in selected rows in a commercial greenhouse reduced peak fungus gnat numbers to about 20% of those in untreated rows. These results suggest that a single inoculative introduction of Geolaelaps sp. nr. acu-leifer, early in the crop cycle, would maintain control of fungus gnat populations in greenhouse cucumber crops at an acceptable level. This predator would also contribute to biological control of western flower thrips by reducing emergence of adults. © 1990, Entomological Society of Canada. All rights reserved.