MONITORING FUNGUS GNATS (DIPTERA: SCIARIDAE) IN CUCUMBER GREENHOUSES

Abstract

AbstractSimple, sticky traps were used to monitor adult sciarid populations, and soil cores were used to monitor larval sciarid populations in commercial cucumber greenhouses. Four methods of sticky-trap placement were compared and it was found that 5 traps in a “W” formation correlated closely with more intensive 12- and 30-trap random placements. All 4 of the greenhouses studied exhibited similar sciarid population patterns in 1983 but only 2 showed large sciarid populations in 1984 and the other 2, using different overwinter sanitation methods, had no detectable sciarid populations. Moth-flies (Psychodidae) were often the most numerous form of small dipteran found on the traps. Larval sciarids occurred in the upper 5 cm of each 10-cucumber bag, and weekly 50-mL core samples showed a range of 0.0 to 1.1 larvae/mL which corresponded to estimated larval populations of up to 2500 per bag. Plants that had succumbed to fungal pathogens and then been sampled immediately for sciarid larvae were found to have fewer larvae per bag than apparently healthy plants. Insect monitoring in cucumber greenhouses has enabled growers to reduce and/or eliminate the need for insecticide applications against sciarids during the growing season.