Epiphyas postvittana (light brown apple moth).

E. postvittana is a small, bell-shaped moth, whose caterpillars feed on a very wide range of plants. The eggs, larvae and pupae can be associated with plant material and readily transported. The pest status of this insect in horticultural crops is very significant. It is native to Australia and was distributed to New Zealand, Hawaii, New Caledonia and the UK with apples [Malus domestica] or other plant material in the late 1800s. It has since spread throughout lowland New Zealand, and in recent years has spread through southern parts of the UK, and Ireland. In Hawaii, it appears to be confined to altitudes above 1100 m, and can largely be considered a pest of temperate regions.

Crystal structure of Epiphyas postvittana pheromone binding protein 3

The insect olfactory system operates as a well-choreographed ensemble of molecules which functions to selectively translate volatile chemical messages present in the environment into neuronal impulses that guide insect behaviour. Of these molecules, binding proteins are believed to transport hydrophobic odorant molecules across the aqueous lymph present in antennal sensilla to receptors present in olfactory sensory neurons. Though the exact mechanism through which these proteins operate is still under investigation, these carriers clearly play a critical role in determining what an insect can smell. Binding proteins that transport important sex pheromones are colloquially named pheromone binding proteins (PBPs). Here, we have produced a functional recombinant PBP from the horticultural pest, Epiphyas postvittana (EposPBP3), and experimentally solved its apo-structure through X-ray crystallography to a resolution of 2.60 Å. Structural comparisons with related lepidopteran PBPs further allowed us to propose models for the binding of pheromone components to EposPBP3. The data presented here represent the first structure of an olfactory-related protein from the tortricid family of moths, whose members cause billions of dollars in losses to agricultural producers each year. Knowledge of the structure of these important proteins will allow for subsequent studies in which novel, olfactory molecule-specific insecticides can be developed.

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

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.