Fungus gnats, Bradysia spp., are a major greenhouse insect pest. Adult fungus gnats prefer to lay eggs in growing medium that is microbially active or contains high levels of peat or bark. A laboratory study was conducted to develop a method to extract fungus gnat eggs from growing media and determine whether fungus gnat females prefer certain growing medium based on the choices provided. The extraction/flotation method uses a salt solution of 1.065 density to float the eggs from the medium. A separatory funnel is used to separate the eggs from the fine particles of media. After processing samples through the separatory funnel, the eggs are separated from the larger particles of media by sieving the sample through a 250 um sieve and collecting the eggs on a 53 um sieve.
Three growing media (Sunshine LC1, Universal Mix, and Metro-Mix 560 with Scott’s Coir) and a moist filter paper (control) were used to determine female fungus gnat egg laying preference. Fungus gnat pupae obtained from a laboratory-reared colony were harvested and adults were allowed to emerge. Adults were collected sexed, and mated. Each pair was allowed to mate for an additional 24 hours. Each chamber held four completely randomized small petri dishes containing the three choices of moist growing media and filter paper. Each female was allowed to remain in the chamber for 48 hours after which eggs were harvested using a separatory funnel and the extraction/flotation method. Based on initial results it appears the fungus gnat females prefer certain growing media.
Species 1: Diptera Sciaridae Bradysia coprophila (Fungus Gnats)
Keywords: greenhouse
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