Cold Disinfestation on Orange for Bactrocera dorsalis (Diptera: Tephritidae)

Cold treatment has been extensively employed for the phytosanitary control of fruit flies for citrus cultivation worldwide. Trials with artificial infestation methods on navel and Valencia oranges at 3 °C and 2 °C against the oriental fruit fly (Bactrocera dorsalis) were conducted, following standard bioassay protocols and large-scale testing. The results showed that the third instar larval stage was the most tolerant stage in both cultivars. The maximum estimated cold treatment time at 3 °C required to produce 99.9968% mortality (LT99.9968) with a 95% confidence level was 16.6 days and 16.2 days for the navel orange and Valencia orange, respectively. Meanwhile, the estimated cold treatment time at 2 °C was 14.8 days for both navel and Valencia oranges, with a 95% confidence level. Furthermore, it was also observed that no survivors came from a total of 104,420 estimated (51,396 for the navel cultivar and 53,024 for the Valencia cultivar) third instar larvae in orange fruits after being subjected to a cold treatment of 3 °C for 17 days. Meanwhile, there were also no survivors from a total of 100,556 (50,740 for the navel cultivar and 49,816 for the Valencia cultivar) third instar larvae in orange fruits after being subjected to a cold treatment of 2 °C for 15 days. The treatments at 3 °C for 17 days and 2 °C for 15 days on oranges, including navel and Valencia, against the oriental fruit fly, surpassed the required mortality assurance of 99.9968% at a 95% confidence level and also met the probit-9 mortality standard. Overall, the application of these results will provide more flexibility for the citrus industry to satisfy quarantine treatment requirements.