Phytophagous insects differ in their degree of specialisation on host plants, and range from strictly monophagous species that can develop on only one host plant to extremely polyphagous species that can develop on hundreds of plant species in many families. Nutritional compounds in host fruits affect several larval traits that may be related to adult fitness. In this study, we determined the relationship between fruit nutrient composition and the degree of host specialisation of seven of the eight tephritid species present in La Réunion; these species are known to have very different host ranges in natura. In the laboratory, larval survival, larval developmental time, and pupal weight were assessed on 22 fruit species occurring in La Réunion. In addition, data on fruit nutritional composition were obtained from existing databases. For each tephritid, the three larval traits were significantly affected by fruit species and the effects of fruits on larval traits differed among tephritids. As expected, the polyphagous species Bactrocera zonata, Ceratitis catoirii, C. rosa, and C. capitata were able to survive on a larger range of fruits than the oligophagous species Zeugodacus cucurbitae, Dacus demmerezi, and Neoceratitis cyanescens. Pupal weight was positively correlated with larval survival and was negatively correlated with developmental time for polyphagous species. Canonical correspondence analysis of the relationship between fruit nutrient composition and tephritid survival showed that polyphagous species survived better than oligophagous ones in fruits containing higher concentrations of carbohydrate, fibre, and lipid. Nutrient composition of host fruit at least partly explains the suitability of host fruits for larvae. Completed with female preferences experiments these results will increase our understanding of factors affecting tephritid host range.

The high invasiveness of phytophagous insects is related to their adaptability to various environments, that can be influenced by their associated microbial community. Microbial symbionts are known to play a key role in the biology, ecology, and evolution of phytophagous insects, but their abundance and diversity are suggested to be influenced by environmental stressors. In this work, using 16 S rRNA metabarcoding we aim to verify (1) if laboratory rearing affects microbial symbiont communities of Zeugodacus cucurbitae females, a cosmopolitan pest of cucurbitaceous crops (2) if temperature, diet quality, and antibiotic treatments affect microbial symbiont communities of both laboratory and wild populations, and (3) if changes in microbial symbiont communities due to temperature, diet and antibiotic affect longevity and fecundity of Z. cucurbitae. The results showed that microbial diversity, particularly the β-diversity was significantly affected by insect origin, temperature, diet quality, and antibiotic treatment. The alteration of gut microbial symbionts, specifically Enterobacteriaceae, was associated with low fecundity and longevity of Z. cucurbitae females feeding on optimal diet only. Fecundity reduction in antibiotic treated females was more pronounced when flies were fed on a poor diet without protein. our study proves the relationship between gut microbiome and host fitness under thermal and diet fluctuation highlighting the importance of microbial community in the adaptation of Z. cucurbitae to environmental stress. Not applicable.

Malathion bait sprays to control medfly, Ceratitis capitata (Diptera: Tephritidae), in Tunisian citrus orchards is expected to be phased out in the near future due to low residue tolerance in the fruits by consumers. Attract and kill strategy that encompasses mass trapping and bait station techniques has become a widespread method for controlling medfly. Effectiveness of two bait station methods (AAL&K® and Ceranock®) and two attractants for mass trapping (Ceratrap® and Starce®) was, respectively, compared with malathion and spinosad in Grombalia and Chott-Mariem experimental sites. Ceranock® and AAL&K® provide effective protection of citrus fruits from medfly attack as confirmed by low rate of damaged fruits of respectively 3.88 and 2.26% compared with malathion (21.63%). Medfly population and rate of fruit damage were significantly lower in Ceratrap® than in Starce® and spinosad treated plots. Rate of fruit damage on Starce® treated plots increased at least three times more than in Ceratrap®, and one-and-half times more than in spinosad treated plots. Ceranock® and AAL&K® bait station devices are a cost-effective alternative to the use of insecticides in citrus orchards and can be used in IPM schemes against medfly in association with other environmentally friendly approaches.