VISUAL AND ODOR STIMULI INFLUENCING EFFECTIVENESS OF STICKY SPHERES FOR TRAPPING APPLE MAGGOT FLIES RHAGOLETIS-POMONELLA (WALSH) (DIPT, TEPHRITIDAE)

The influence of odor and visual stimuli on the effectiveness of sticky red spheres in capturing Rhagoletis pomonella (Walsh) flies in a commercial orchard unsprayed after June was investigated. Unbaited 8-cm red spheres (presently recommended size) captured significantly more female an male R. pomonella flies than unbaited 10-cm red spheres. Sticky 8-cm red spheres baited with 1, 2, or 4 2-dram polyethylene vials containing 2.5 ml butyl hexanoate at a distance of 15, 30, or 60 cm from the sphere captured significantly more female and male R. pomonella than unbaited spheres. Spheres baited with 2 or 4 vials of butyl hexanoate, however, did not significantly increase R. pomonella captures compared with spheres baited with 1 vial. The distance of 1, 2 or 4 butyl hexanoate vials within a range of 15-60 cm around a sphere had no significant effect on R. pomonella captures. A combination of 1 capped 2-dram vial (with a single 3-mm opening) containing ca. 5 g ammonium carbonate and 1 vial of butyl hexanoate, as lures, increased female and male R. pomonella captures over unbaited spheres significantly more than either 2 vials of ammonium carbonate alone or 2 capped vials of butyl hexanoate, between which there was no significant difference. A protective conical roof partially obscuring a sphere, regardless of colour, significantly reduced R. pomonella captures. The relevance of these findings to potential improvement in use of baited spheres for R. pomonella control in commercial orchards is discussed.