Search

Response of endophytic fruit fly species (Tephritidae) to larval crowding is a form of scramble competition that may affect important life history traits of adults, such as survival and reproduction. Recent empirical evidence demonstrates large differences in adult life history traits, especially longevity, among Mediterranean fruit fly (Ceratitis capitata; "medfly") biotypes obtained from different regions of the world. However, whether the evolution of long lifespan is associated with response to stress induced by larval crowding has not been fully elucidated. We investigated, under constant laboratory conditions, the response of a short- and a long-lived medfly biotypes to stress induced by larval crowding. Survival and development of larvae and pupae and the size of resulting pupae were recorded. The lifespan and age-specific egg production patterns of the obtained adults were recorded. Our findings reveal that increased larval density reduced immature survival (larvae and pupae) in the short-lived biotype but had rather neutral effects on the longed-lived one. Only larvae of the long-lived biotype were capable of prolonging their developmental duration under the highest crowding regime to successfully pupate and emerge as adults. Response of emerging adults to larvae crowding conditions was similar in the two medfly biotypes. Those individuals emerging from high larval density regimes had reduced longevity and fecundity. Long-lived biotype individuals, however, appeared to suffer a higher cost in longevity compared with the short-lived one. The importance of our findings to understand the evolution of long lifespan is discussed.

BACKGROUND Linalool is a natural scent, found in essential oils (EOs) of several plants. It is widely used as a fragrant, also possessing toxic, oviposition‐deterrent and repellent properties against many insect species. Ceratitis capitata (medfly) is one of the most notorious insect pests for international fresh fruit production. Despite the available information on the repellent effects of EOs on herbivorous insects, possible oviposition‐deterrent effects of linalool against C. capitata remain unknown. OBJECTIVES AND RESULTS We tested whether different linalool concentrations, application methods on fruit hosts and time since application elicited oviposition‐deterrence on medfly, from bitter oranges, apples and nectarines, under constant laboratory conditions. We also tested possible repellent properties of linalool on adult medflies in field conditions. Females drilled fewer oviposition stings and deposited fewer eggs per fruit in all linalool‐treated hosts. Spraying and topical‐droplet application were the most efficient methods on bitter oranges, although spraying was the least effective method in apples. Bitter oranges and nectarines that were offered to females immediately post‐exposure to linalool received more oviposition stings and eggs than those offered 3 days post‐exposure to linalool solutions. Conversely, apples tested 3 days following linalool application received significantly more oviposition stings and eggs than those tested immediately and 1 day post‐exposure. More adults in total, and more females, were captured in traps located on untreated‐control than on linalool‐treated trees, especially in citrus hosts. CONCLUSION: Linalool has a potential future use in environmentally friendly control strategies against C. capitata. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Female Mediterranean fruit flies (medfly) Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) perceive both qualitative and quantitative aspects of citrus fruit chemistry. However, the behavioural and biological adjustments of this response remain largely unknown. In the present study, the ovipositional responses of gravid female medflies to essential oils (i.e. the most critical resistance factor to medfly infestation) of various citrus fruits are investigated. In dual-choice (treatment versus distilled water control) experiments, females lay significantly more eggs into pre-punctured hollow oviposition hemispheres (domes) provided with 1 µL of citrus peel oil from sweet orange, satsuma mandarin, bitter orange, grapefruit and lemon compared with odourless domes. No-choice tests show a weak effect of lemon essential oils in stimulating oviposition. The female ovipositional response to sweet orange oil (the most active in eliciting oviposition) is dose-dependent. Additionally, limonene, the most abundant chemical in all citrus oils, stimulates oviposition, whereas linalool, a representative compound of immature citrus fruit associated with high toxicity against immature stages of fruit flies, has a significant deterrent effect. In further no-choice tests, females lay approximately 23% fewer eggs in limonene (93%) (amount found in orange oil) and 60% fewer eggs in limonene 93% plus linalool 3% (approximately 10-fold the amount found in orange oil) mixtures, relative to sweet orange oil. The results suggest that the limonene content accounts largely (but not completely) for the ovipositional responses observed in sweet orange oil, whereas high linalool proportions are capable of significantly masking and/or disrupting its stimulatory effects in citrus oils. The importance and practical implications of these findings with respect to understanding how citrus fruit chemistry influences the ovipositional responses of medfly is discussed. [ABSTRACT FROM AUTHOR]