Static flow, two-choice olfactometer designed to screen compounds that attract or repel gravid fungus flies, Lycoriella mali

Lycoriella mali Fitch (Diptera: Sciaridae) is the major insect pest species of the white button mushroom, Agaricus bisporus, throughout the world causing severe damage. Larvae of the flies feed on the mycelia and tunnel into the caps and stems of mushrooms.  Moreover, adults of L. mali act as vectors for spreading fungus spores of Trichoderma aggressivum Green Mold disease, which leads to additional crop losses. Thus, control of L. mali is a necessity worldwide. However, insecticide options are limited because they are subject to label restrictions of the number of applications per season or the total amount of active ingredient applied. In addition, repeated applications produce undesirable effects, such as insecticide residues and reduced populations of natural enemies. It is therefore essential to develop efficient monitoring methods, including damage thresholds and alternative control strategies. Here we describe efforts to develop discriminatory behavioral assays that can be used to screen synthetic compounds that attract or repel gravid L. mali adults. We designed a static-flow two-choice olfactometer that is able to discriminate the primary preference of a host-seeking female fly. Preliminary data suggest that female flies significantly prefer spawned mushroom compost containing A. bisporus mycelia compared to water agar controls, but they do not significantly prefer spawned water agar containing A. bisporus mycelia versus those same controls. These intriguing results suggest that gravid female flies are attracted to additional volatile compounds from mushroom compost other than those that may be emanating from actively growing A. bisporus mycelia.