Experimental high-density trapping of social wasps: target kairomones for workers or gynes for drones?

ABSTRACT Social wasps are amongst the most loathed exotic predators in New Zealand, with widespread adverse impacts on native ecosystems and fauna. Sustainable alternatives to pesticides are sorely needed in Fuscospora (beech) forests. We tested a new semiochemical evaluation protocol to assess the extent of high-density trap competition as an indicator of mass trapping, in an open landscape adjacent to a beech forest near Cass (Canterbury, New Zealand), for potential worker or drone removal. We tested the kairomone lure using a before-after control-impact design at a 1-ha scale with a grid of 25 bucket traps as a high-density trapping treatment (three replicates). The trial was affected by a major inundation event and catches declined steadily in both treatments for the month following, and treatment effects were not significantly different. Drone captures in sticky traps showed a dose response in catch to 1, 3 or 10 gynes (virgin queens). Sticky traps baited with three gynes in a 5 × 5 array over 1 ha (four replicates), caught a mean of 7.39 (±0.88) drones per trap per day across the high density and control traps (n = 116), but there was no difference in the number of drones caught per central trap in the control and treatment plots (n = 4 per plot), demonstrating the limitations of our methods under extreme population pressure in such a mobile species. It is proposed that the gyne sex pheromone be identified and investigated for potential use in area-wide suppression, as it holds more promise as an attractant than the kairomones tested.http://www.zoobank.org/urn:lsid:zoobank.org:act:C0809A1F-87C2-431C-BA14-548F00D954F9