The use of plant volatiles for host location by an ash (Fraxinus) specialist, Caloptilia fraxinella

Abstract

Volatile organic chemicals (VOCs) are used by female moths to find host plants for oviposition and specialist moths can be highly tuned to the volatile signature of their host plant. The ash leaf-coneroller, Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) specializes on ash (Fraxinus spp.) (Oleaceae). Its introduction to urban forests in the Canadian Prairie Provinces on both green, F. pennsylvanica, and black ash, F. nigra, offers the opportunity to test odor-mediated host location to two host-plant species. In laboratory and field experiments, C. fraxinella adults oriented to volatiles released from ash seedlings. The antennae of mated female C. fraxinella consistently detected five VOCs released from black and green ash, four of which were common to both species. Blends of natural and synthetic VOCs found to elicit an antennal response were tested in wind tunnel and field bioassays. Synthetic and natural VOCs elicited as much oriented flight from mated female C. fraxinella as ash seedlings, but did not elicit contact with the VOC lure in the wind tunnel. In the field, traps baited with blends of synthetic copies of black and green ash VOCs did not attract more female C. fraxinella than unbaited control traps. These experiments lay the foundation for further research to develop semiochemical lures to attract female C. fraxinella.