Effect of fly density and holding period on quality parameters of pre-release chilled adults of Anastrepha obliqua (Diptera: Tephritidae)

Packing, shipping, holding and releasing methods of sterile tephritid fruit flies for the control of pest populations have recently received special attention because they are the final steps in the application of the sterile insect technique (SIT). In this study, we examined the effect of four holding densities, 0.524, 0.599, 0.674 and 0.748 sterile adults/cm², and four holding periods (5, 6, 7 and 8 days) in sterile West Indian fruit flies, Anastrepha obliqua (Diptera: Tephritidae). The key parameters of adult fliers (AF, also known as absolute fliers) and adult survival under stress were measured. We also compared two methods to determine the percentage of AF (called the tray and sample methods) after the holding period and the chilling process. Our results indicate that differences in holding densities and holding periods may not affect the percentage of AF and the survival of sterile adults if they are supplied with enough food and water, allowing the release of higher numbers of sexually mature sterile males. When estimating the percentage of AF, the evaluated methods resulted equivalent and reliable, but the sample method showed a clear advantage by allowing the use of lower numbers of sterile flies to perform the test, which may represent important savings in SIT programmes. These findings will require further studies on sexual competitiveness in field cages to better determine the optimal management of sterile flies in FERFs.