Market access is a key priority for the Australian vegetable industry. The presence of quarantine pests such as Cucumber fly in some growing areas requires fruit to be treated and/or certified as being free from live quarantine pests before accessing important pest-free markets. Up until recently a single postharvest dip, spray or flood treatment of fresh Australian zucchinis in/with a 412.4mg/L solution of fenthion was the approved quarantine treatment for access of these fruit to New Zealand and other fruit fly sensitive parts of Australia (e.g. Tasmania, Western Australia and South Australia). Rulings by the Australian Pesticides and Veterinary Medicines Authority (APVMA) restricted the use of fenthion on human food due to public health concerns with residues. A new method of applying fenthion to acquire quarantine security was devised by Hannay- Douglas Pty Ltd using a much lower concentration of fenthion (100mg/L) but applied twice (24h apart). This ensures residues that are well below the maximum residue limit stipulated by the APVMA. This report describes the results of efficacy tests of this prototype treatment carried out on the main quarantine fruit fly pest of zucchinis, the Cucumber fly (Bactrocera cucumis, French). Tests carried out showed that eggs, first instar larvae, second instar larvae and third instar larvae dominated larval populations within infested fruit at certain times after initial egg laying (oviposition). Infested fruit were dipped in the 100mg/L fenthion solution for 60s at each of these larval development times (and the treatment repeated 24h later) so that there was assurance that each life stage that would be likely to be found infesting fresh zucchinis was treated. Survival of insects from Control fruit that were infested but not fenthion dipped (they were water dipped) was used to estimate the number of insects treated in the fenthion dipped fruit and, hence, treatment induced mortality. Experiments were replicated three times in