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Treating Mexican grapefruit with gibberellic acid (GA3) before color break, significantly delayed peel color change and increased peel puncture resistance, but it did not reduce grapefruit susceptibility to Mexican fruit fly, Anastrepha ludens (Loew) attack under natural conditions. Despite GA3 treatments, larval infestation levels increased with higher fruit fly populations, which also increased as the season progressed. Late in the season, infestation levels were even higher in GA3-treated fruit compared with untreated fruit, possibly because treated fruit were in better condition at that stage. Egg clutch size was significantly greater in very unripe, hard, GA3-treated fruit at the beginning of the harvest season and in December, compared with control fruit. Under laboratory conditions, egg injection into different regions of the fruit suggested that A. ludens eggs are intoxicated by peel oil content in the flavedo region. However, A. ludens' long aculeus allows females to oviposit eggs deeper into the peel (i.e., albedo), avoiding toxic essential oils in the flavedo. This makes A. ludens a particularly difficult species to control compared with other citrus-infesting species such as Anastrepha suspensa (Loew), Anastrepha fraterculus (Wiedemann), and Ceratitis capitata (Wiedemann) (fly species with significantly shorter aculei), which can be effectively managed with GA3 sprays. We discuss our findings in light of their practical implications and with respect to the oviposition behavior of various fruit flies attacking citrus.

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This chapter concentrates on three pestiferous Anastrepha species considered highly polyphagous and identified as potential exotic invaders: A. ludens, A. obliqua and A. grandis. It provides a comprehensive overview of the published information on these three species to aid further research efforts and to facilitate decision-making processes in the areas of management and regulatory entomology. Emphasis is given on recent studies of behaviour, especially those related to oviposition and host selection (and use), life history (including variation on the duration of larval development according to type of host), ecology and population dynamics. This review also discusses traditional control methods such as field sanitation, chemical and biological control, sterile insect technique, more recent efforts on biorational management and use of new tools. Short- and long-term research needs are considered.

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