Tephritid-free quarantine procedure for avocados from Hawaii is not effective
In USA, in 1990, an infestation-free quarantine procedure had been set up for avocado (Persea americana cv. 'Sharwil') grown in Kona, Hawaii (US) and exported to the contiguous United States. This procedure was based on the assumption that 'Sharwil' avocado fruits on trees are not suitable hosts for fruit flies (Ceratitis capitata (EPPO A2 quarantine pest), Bactrocera cucurbitae and B. dorsalis (both EPPO A1 quarantine pests)). Though literature data was contradictory with regard to the relative resistance of 'Sharwil' avocado, further laboratory and field studies carried out over 3 years confirmed that 'Sharwil' avocado was not a host for these fruit flies provided fruit is still attached to the tree or when fruits are harvested with stem attached. Therefore, it was required that mature green fruits with pedicel firmly attached should be harvested only from trees that had been certified by APHIS as being truely 'Sharwil'. No conventional quarantine treatment was required. However, in 1992 during routine inspections, 'Sharwil' fruits infested by B. dorsalis have been found. The authors have made further studies in order to explain the failure of this procedure. In the field, they have observed that although 'Sharwil' avocados are poor hosts, B. dorsalis can be found on mature fruits. They suggested that differences in sampling methods (e.g. number of fruit samples and timing of sampling) used in the different studies may explain the discrepancies between their results and previous studies.
Sources
Liquido, N.J.; Chan, H.T. JR; McQuate, G.T. (1995) Hawaiian Tephritid fruit flies (Diptera): integrity of the infestation-free quarantine procedure for 'Sharwil' avocado.
Journal of Economic Entomology, 88(1), 85-96.