Bioassay for evaluating attraction of the phorid fly,Megaselia halterata to compost colonized by the commercial mushroom,Agaricus bisporus and to 1-octen-3-ol and 3-octanone

A bioassay chamber was developed to evaluate the attraction of the phorid fly pest,Megaselia halterata (Wood) (Diptera, Phoridae), to volatiles from mushroom compost colonized by the commercial mushroom,Agaricus bisporus (Fungi, Agaricaceae) and to its volatile constituents, 1-octen-3-ol and 3-octanone. The bioassay chamber consisted of a large round container which was attached, via glass tubes, to three removable sample cups situated below the container. Once a fly had entered a sample cup, the flatly cut glass tubes prevented the flies from readily returning to the release chamber and, in effect, was a pit fall trap which kept the flies in the cups until the flies were counted. Holes in the bottom of the cups and removal of 20 ml of air from the chamber to fill the entrance tubes with volatiles from the cups were necessary for the success of the bioassay. Mated and unmated femaleM. halterata and, to a lesser extent, mated males preferred spawned compost (compost well colonized by fungal mycelia) relative to unspawned compost or blank cups. Unmated males were not attracted to spawned compost. Males and females were not attracted to unspawned compost. No attraction of male or femaleM. halterata to the spawned compost volatiles, 1-octen-3-ol and 3-octanone, could be demonstrated under various experimental conditions. These two compounds seemed to deter females at high concentrations.