Résumé
The oriental fruit fly, Bactrocera dorsalis, a major invasive fruit pest whose females damage many host plants, has been established in La R´eunion since 2017 and threatens to spread in Europe [3]. The Sterile Insect Technique (SIT), a biological control method in which sterile insects are released to suppress populations, is a well- documented control strategy which has been successfully implemented in di!erent countries [4]. So far, male-only releases have been privileged and studied [1, 4], but in practice e”cient sexing methods do not exist for every species and are expensive. Therefore bisexual releases have to be considered. The impact of bisexual releases has been studied in [2] through a probabilistic model, however it has not yet been investigated with deterministic methods. We propose a dynamical system model of SIT incorporating both monosex- ual and bisexual release strategies, aiming to identify the optimal approach given species-specific biological parameters. We establish the existence of a critical release rate, #crit(p), depending on the release sex ratio p, above which pest extinction is the only equilibrium and is globally asymptotically stable, and below which there also exist generically two strictly positive equilibria. By analyzing the dependence of #crit on p, we identify conditions under which bisexual releases minimize the crit- ical release rate, conditions that are met by B. dorsalis. Finally, we examine the dependence of #crit on various biological parameters and compare realistic bisexual release strategies where the sex-ratios of released and wild insects are the same, with monosexual release strategies.