Hawaiian tephritid fruit flies (Diptera): integrity of the infestation-free quarantine procedure for 'Sharwil' avocado.

In 1990, the infestation-free quarantine procedure for 'Sharwil' avocados grown in Kona, HI, was approved based on the assumption that fruits on trees are not hosts of tephritid fruit flies. In February 1992, the infestation-free quarantine procedure was suspended because of discovery of oriental fruit fly, Bactrocera dorsalis (Hendel), larval infestation in fruits on trees in certified orchards. Subsequently, an intensive field study was conducted to determine the level of tephritid fruit fly infestations in 'Sharwil' fruits. Results gathered negated two assumptions of the infestation-free quarantine procedure. First, the procedure assumed that only immature and mature green fruits are attached on trees; our data showed that, although most fruits on trees were either immature or mature green, a few ripe fruits occurred during the fruiting season. Second, the procedure assumed that mature green fruits have absolute resistance to tephritid fruit flies occurring in Hawaii; our field data showed that mature green 'Sharwil' avocados are suitable hosts of oriental fruit fly, albeit poor hosts. We present several hypotheses that may explain the failure of the infestation-free quarantine procedure for 'Sharwil' avocados. Morphological, physical, and chemical attributes of maturing 'Sharwil' fruits that may be useful in developing indices of fruit maturity and quality are also presented.