Titre de la thèse (en anglais): Change in attraction and in oviposition of female moths in relation to maize plant’s statement within a community of lepidopteran maize stemborers
Résumé (en anglais): Lepidopteran female oviposition choices are known to be guided by infochemicals from infesting stages (eggs or larvae) from other conspecifics, which serve to adjust population sizes to available resources with a preference for un-infested plants. However, it was recently shown that females of maize stemborer moths namely Busseola fusca (Fuller) (Lepidoptera: Noctuidae), Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae) preferentially oriented towards volatile organic compounds (VOCs) emitted by both conspecific- and heterospecific-infested plants compared to their uninfested plant counterparts. Moreover, the maize stemborers species associated to maize are rarely present in wild grasses during the non-planting season and thus likely seeking refugia in maize stalk residues from the previous harvests “awaiting” the next cropping season. Therefore, the annual species dominance on maize will also depend on their previous abundance in maize residues. Based on these findings, it is hypothesized that maize residues ensure the carry-over of these stemborers species during the non-cropping season and that female moth preference for both con- and heterospecific infested maize plant over their un-infested counterparts vary within the cropping season (i.e. at the beginning and later during the cropping season).
The work will focus on the study of the ecological rationale associated with female moth preference for both con- and hetero-specific infested maize plants over their un-infested counterparts and their variation with the cropping season by a combination of field and laboratory experiments. Field tests will allow characterising preferences of the three stemborers species for different resource quality (uninfested vs conspecific or heterospecific infested plants). To understand these choices, we will conduct chemical analyses of their VOCs, and record their behavioural and electrophysiological response to key chemicals. It is hoped that the data obtained will explain the observed variation in stemborers oviposition behaviour in the field. Additionally, these findings will allow the development a multi-species lure targeting female moths. The envisaged kairomone trap will add to existing control tools against Lepidoptera stemborers.