Plant Chemicals and the Sexual Behavior of Male Tephritid Fruit Flies

The extent to which behavioural choices reflect fine-tuned evolutionary adaptation remains an open debate. For herbivorous insects, the preference-performance hypothesis (PPH) states that female insects will evolve to oviposit on hosts on which their offspring fare best. In this study, we use meta-analysis to assess the balance of evidence for and against the PPH, and to evaluate the role of individual factors proposed to influence host selection by female insects. We do so in an explicitly bitrophic context (herbivores versus plants). Overall, our analyses offer clear support for the PPH: Offspring survive better on preferred plant types, and females lay more eggs on plant types conducive to offspring performance. We also found evidence for an effect of diet breadth on host choice: female preference for 'good quality plants' was stronger in oligophagous insects than in polyphagous insects. Nonetheless, despite the large numbers of preference-performance studies conducted to date, sample sizes in our meta-analysis are low due to the inconsistent format used by authors to present their results. To improve the situation, we invite authors to contribute to the data base emerging from this work, with the aim of reaching a strengthened synthesis of the subject field.

Recently, a growing number of plant essential oils (EOs) have been tested against a wide range of arthropod pests with promising results. EOs showed high effectiveness, multiple mechanisms of action, low toxicity on non-target vertebrates and potential for the use of byproducts as reducing and stabilizing agents for the synthesis of nanopesticides. However, the number of commercial biopesticides based on EOs remains low. We analyze the main strengths and weaknesses arising from the use of EO-based biopesticides. Key challenges for future research include: (i) development of efficient stabilization processes (e.g., microencapsulation); (ii) simplification of the complex and costly biopesticide authorization requirements; and (iii) optimization of plant growing conditions and extraction processes leading to EOs of homogeneous chemical composition.