Yeasts influence host selection and larval fitness in two frugivorous carpophilus beetle species

We explored how gut-associated yeasts influence olfactory behaviour and resource use in two pest species of Carpophilus beetle that co-exist in Australian stone fruits. Molecular analysis of yeasts isolated from the gut of C. davidsoni (prefers ripe fruits) and C. hemipterus (prefers overripe and rotting fruits) revealed that the predominant species were Pichia kluyveri and Hanseniaspora guilliermondii. In olfactory attraction and oviposition trials, adult beetles preferred H. guilliermondii over P. kluyveri, and follow up GC-MS analysis revealed unambiguous differences between the odour profiles of these yeasts. In contrast to behavioural trials, larval feeding assays showed that fruit substrates inoculated with P. kluyveri yielded significantly faster development times, higher pupal mass, and a greater number of adult beetles, compared to H. guilliermondii — in other words, the lesser preferred yeast (by foraging adults) was more suitable for larval survival. Moreover, whilst larvae of both species survived to adulthood when fed solely on P. kluyveri (i.e. without a fruit substrate), only larvae of C. davidsoni could develop on H. guilliermondii; and only C. davidsoni reached adulthood feeding on a yeast-free fruit substrate. We discuss how these findings may relate to adaptations towards early colonising of fruits by C. davidsoni, enabling differences in resource use and potentially resource partitioning in the two beetles. More broadly, consideration of microbial interactions might help develop host selection theory. Our results could pave the way to more powerful attractants to mass-trap and monitor Carpophilus pests in fruit orchards.</p

Yeast species affects feeding and fitness of Drosophila suzukii adults

Yeasts play an important role in the life cycle and biology of the insect pest Drosophila suzukii (Matsumura), commonly known as the spotted wing drosophila (SWD). Adult and larvae of this species are known to feed and benefit from yeast in their diet. In addition, yeasts were found to be attractive to SWD and were repeatedly found to be associated with SWD. Among those, Hanseniaspora uvarum is the most commonly mentioned. The present study explores the chemical composition and the effects of three H. uvarum strains and five yeast species (Saccharomyces cerevisiae, Candida sp., Issatchenkia terricola, Metschnikowia pulcherrima and Saccharomycopsis vini) in the diet of SWD adults. The different yeast species used in this study influenced mortality, fecundity and ingestion by SWD females. Hanseniaspora uvarum and S. vini were preferably ingested and increased fecundity of SWD females. The intra- and extracellular concentrations of compounds, such as amino acids, carbohydrates, sugar alcohols and organic acids, produced or consumed by yeasts differed among the species. Knowledge of the interaction of different yeast species with SWD and specific differences in the profile of compounds of yeast can help to improve the development of control strategies against the insect pest by promoting the ingestion of attract-and-kill formulations based on the combinations of yeasts and an appropriate insecticide