Semiochemical-mediated attraction and oviposition in pyralid moths

Moths use chemical signals emanating from food to find sites for oviposition and subsequent larval feeding. By identifying these odours, novel approaches to pest management can be developed, such as monitoring of females in pest populations. The pyralid moths studied in this thesis, the almond moth (Ephestia cautella), the Mediterranean flour moth (E. kuehniella) and the Indian meal moth (Plodia interpunctella) are severe worldwide pests of a variety of stored products. The aim was to find food-derived chemical signals that are attractive to and mediate oviposition behaviour in females.

Both sexes of E. cautella and P. interpunctella were attracted to and landed on three chocolate products in a flight tunnel. Chocolate is mainly infested by E. cautella, but the chocolate products were also suitable food for P. interpunctella in our laboratory. Behavioural activity was also observed when testing extracts of the chocolate products. Three compounds were identified by mass spectrometry after electrophysiological investigation of the moths' antennae, i.e. ethyl vanillin, nonanal and phenylacetaldehyde. A blend of the three compounds evoked the whole behavioural sequence including landing rates corresponding to that of the chocolate products.

Chocolate extracts were active on antennae of both sexes of E. kuehniella as well. This species is specialised on cereal products, making the responses to chocolate compounds unexpected, but the identified compounds, namely benzyl alcohol, nonanal and phenylacetaldehyde, might also be found in cereal products. The chemicals stimulated oviposition in E. kuehniella females when presented one by one. A blend of the three compounds trapped males in a small-scale trapping experiment in tents. The results from these two behavioural studies indicate that chocolate-derived volatiles might have a future in pest management of the moths.

Water was attractive to E. cautella in a trapping experiment in a chocolate factory. The water did not trap any E. kuehniella when tested in a flour mill. Water is attractive to E. cautella since it is probably a limited resource for this species, whereas E. kuehniella is more adapted to dry habitats.

Experience was shown to play a role in the search for food in E. cautella and P. interpunctella. The influence of exposure during adult emergence was most pronounced on the most crucial behaviour for larval viability, i.e. the oviposition. Flight behaviour, in response to food odours, was also enhanced by prior exposure during adult emergence and larval feeding experience had some enhancing effect on E. cautella flight behaviour.