WIND-TUNNEL ASSAYS OF OLFACTORY RESPONSES OF FEMALE RHAGOLETIS-POMONELLA FLIES TO APPLE VOLATILES - EFFECT OF WIND-SPEED AND ODOR RELEASE RATE

The effect of wind speed and odour release rate on female Rhagoletis p omonella (Walsh) (Diptera: Tephritidae) responses to synthetic host ap ple volatiles was studied in a wind tunnel bioassay. Three apple tree models were placed in the wind tunnel (upwind, central and downwind se ctions) after which flies were released individually on the central tr ee and their movements observed for 15 min. The experiment was designe d as a two-way factorial with no odour and odour release rates of ca. 18 and ca. 500 mug h-1 and still air and wind speeds of 0.8 and 1.6 m s-1 as treatments. Both wind speed and odour had significant effects o n flight frequency (landings min-1) and general fly activity. Fly move ment decreased as wind speed increased from 0 m s-1 to 0.8 and 1.6 m s -1, but this decrease was attenuated when air carried apple volatiles. When air was odour-free, flies exposed to 1.6 m s-1 wind moved downwi nd.