Minor components modulate sensitivity to the pheromone antagonist Z11-14:Ac in male lightbrown apple moth, Epiphyas postvittana (Lepidoptera: Tortricidae) in the field

Abstract

Epiphyas postvittana is a major horticultural pest in many countries, including New Zealand. Recently, two minor components (E)-11-tetradecen-1-ol and (E)-11-hexadecenyl acetate were found to increase the attraction of a previously identified two-component sex pheromone (95:5 blend of (E)-11-tetradecenyl acetate [E11-14:Ac] and (E,E)-9,11- tetradecadienyl acetate [E9,E11-14:Ac]) of Epiphyas postvittana. We hypothesised that the interaction between these minor components and the behavioural antagonist (Z)- 11-tetradecenyl acetate (Z11-14:Ac) would modulate its antagonistic effect. The effect of increasing the ratio (0.5-10%) of Z11-14:Ac was tested in traps baited with E11-14:Ac and E9,E11-14:Ac (95:5), with or without the addition of the two minor compounds. Catch decreased as the percentage of Z11-14:Ac increased (χ2=108.74; d.f.=9; P<0.001). Overall, more moths were caught in traps baited with four- vs two-component lures (χ2=9.81; d.f.=1; P=0.002); in pair-level comparisons, significant differences in catch number between the two- and four-component lures were observed when the E11-14:Ac : Z11-14:Ac ratio was 99:1 (P=0.031) or 98:2 (P=0.047). The addition of the two minor components mitigated the reduced catch effect due to lower proportions of E11-14:Ac and the presence of 1-2% antagonist.