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In southern California, the sterile insect technique has been used since 1994 to prevent establishment of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This method involves the continual mass release of sterile flies, which suppress or eliminate any introduced wild fly populations. In addition, Jackson traps baited with trimedlure are deployed throughout the preventative release region for the dual purpose of detecting wild flies and monitoring released sterile flies. Sterile fly recapture data for a 3-yr period was compared with climate and to host plant (in which traps were placed). Precipitation was negatively correlated; and temperature and relative humidity were positively correlated with fly recapture levels. The highest numbers of flies were recaptured during trapping periods associated with intermediate relative humidity and temperature, and low precipitation. Flies were recaptured throughout the entire year, in traps that had been frequently relocated to host plants with fruit. This finding suggests that these flies were capable of locating acceptable fruit in a variety of abiotic conditions. However, these data do not necessarily suggest that measurements unimportant in explaining sterile fly recapture are not of value in determining other outcomes important to the goals of sterile release programs, such as reducing the likelihood of establishment of an introduced wild Mediterranean fruit fly population. Future research might build on these results in developing more precise models useful in predicting recapture of sterile flies.

At Mediterranean fruit fly rearing centers, genetic sexing strains such as the male-only temperature sensitive lethal (tsl) strains, are replacing many of the older bisexual strains, such as Maui-93. Three tests were performed to compare the performance of the Vienna-4 (which carries tsl) and Maui-93 strains. Using standard laboratory quality control tests, the Maui-93 strain had higher percent fliers and a lower percentage deformed and partially eclosed flies. Analyses of data from field mark-recapture tests with Jackson traps failed to find significant differences in recapture numbers between the two strains. In field cage survivorship tests, the Vienna-4 strain showed significantly lower mortality in comparison to the Maui-93 strain. These results suggest that although the quality of Vienna-4 flies is lower than Maui-93 at the time of adult emergence, it is comparable with or better than Maui-93 several days later, because weaker flies have been eliminated from the cohort. The benefits of releasing only sterile males, instead of both males and females, was not factored into the quality assessment in this study, but would be an additional benefit in using a strain that carries a tsl mutation.