Résumé
This study investigates the Sterile Insect Technique (SIT) combined with Entomopathogenic Fungi soil treatment (EPFS) to control two major pests: the medfly and the oriental fruit fly. SIT involves releasing sterile males to mate with wild females, but the challenge lies in female polyandry (re-mating) and residual fertility in sterile males.
We develop a continuous releases SIT model with single-and double-mated females, but with a new way of taking into account the residual fertility parameter, ε. We also consider the case where sterile males competitiveness may decline between the first and the second mating. A key finding is that insect elimination, at least locally, with SIT can only occur when the product of the residual fertility, ε, and the basic reproduction number of single-and double-mated sterile females, R_S , is less than one. We also show the existence of a sterile males release threshold, above which global elimination is possible. When εR_S is greater than one, elimination is impossible whatever the size of the sterile males releases. We also extend our results to periodic releases. We illustrate our theoretical results with numerical simulations, using parameters from the medfly, with and without ginger root oil (GRO) treatment, and the oriental fruit fly, with and without Methyl-Eugenol (ME) treatment. Both treatments are known to enhance sterile male competitiveness. We also show that combining SIT with EPFS can greatly improve the SIT efficiency, and, in particular, reduce the constraint on residual fertility.
Re-mating and residual fertility can strongly influence the efficiency of SIT. However, this mainly depends whether SIT is used in combination with EPFS or not, and also on the knowledge on sterilemated females parameters that seem, so far, to be superficially studied in many SIT programs.