Field attaction response of raspberry clearwing moths, Pennisetia hylaeiformis Lasp. (Lepidoptera: Sesiidae), to candidate pheromone chemicals

Male Pennisetia hylaeiformis moths were highly attracted to blend sources of (E,Z)-3,13-octadecadienyl acetate (E3Z13-18:Ac) and its corresponding alcohol analogue (E3Z13-18:OH) in field tests conducted in stands of wild raspberry (Rubus idaeus) in southern Germany in 1980-85. The optimum blend ratio of the two chemicals, as measured by the number of males arriving at the source per unit time, was found to range from 100/30 to 30/100. However, even the single chemicals attracted males, but only from a short distance. Tests in which two different blend sources were offered simultaneously to flying males at close distance (below 5 m) showed that generally more males landed at the source with the higher Ac/OH ratio. Thus, the 100/100 mixture of the two compounds, most attactive over long range, was also the most effective in eliciting landing responses. There was no obvious difference in male courtship patterns at lure sources of different composition. Tree silhouettes or other visual markers did not appear to play a crucial role in the pheromonal orientation process. Males only responded to the synthetic baits during daylight, with a pronounced peaking in the later afternoon. The two chemicals displayed their synergistic effects on male long-rage orientation even when released from separate dispensers. Thus, separate sources of E3Z13-18:Ac and E3Z13-18:OH, each barley attractive over greater distances when offered alone, attracted numerous males when exposed simultaneously up to 1 m apart (perpendicular to wind direction). A 100/100 blend source exposed upwind from an infested raspberry stand lured males over distances up to 1000 m. These long-range flights were straight forward, even occurring over bare fields devoid of trees and bushes. Sources containing the two chemicals in ratio such as 100/10 or 10/100 had a considerably smaller drawing range. The field behavioural data, together with electrophysiological, suggests that the two compounds are primary components of the as yet chemically unidentified P. hylaeiformis female pheromone