Enhancing efficacy of Mexican fruit fly SIT programmes by large-scale incorporation of methoprene into pre-release diet

The juvenile hormone analogue, methoprene, has been documented to accelerate the development of reproductive competence and sexual signalling of Caribbean (Anastrepha suspensa), the Mexican (Anastrepha ludens), the South American (Anastrepha fraterculus) and West Indian (Anastrepha obliqua) tephritid fruit flies. The incorporation of methoprene into sterile fly release protocols at fly emergence and handling facilities is a key step required for large-scale application of the technology to field release strategies. The goal of our study was to develop a method to supply, in large scale, methoprene to sterile Mexican fruit flies for release in the current Sterile Insect Technique (SIT) programme in Mexico. In field cage tests, the isolation index of sterile males after treatment with methoprene was reduced, increasing the percentage of mating between laboratory sterile males and wild females. In laboratory trials, males fed a diet containing 0.05% or 0.1% methoprene mated 4-day earlier than untreated control males. In a pilot area tested in 3500ha to measure the impact of the sterile releases when methoprene was supplied, no adult wild flies were detected and no larvae were found after sampling more than 330kg of fruit both in the treated and untreated blocks. Based on the results obtained in this study, we recommend the incorporation of the methoprene on adult diet to improve the Mexican fruit fly male sexual performance when release in the field, contributing to the increase in the cost-effectiveness of the SIT programme.