Citrus Research International, P.O. Box 28, Nelspruit 1200, South Africa.
J Econ Entomol. 2011 Aug;104(4):1174-9. doi: 10.1603/ec10434.
South Africa currently exports fresh citrus (Citrus spp.) fruit to Japan using an in-transit cold treatment protocol of 14 d or 12 d at temperatures <0 degrees C for treatment of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in 'Clementine' mandarins (Citrus reticulata Blanco) and other citrus types, respectively. To reduce the risk of chilling injury with this treatment, research was conducted with temperatures >0 degrees C. Earlier South African research had shown that young (6-d-old) larvae were slightly more tolerant of cold treatment and that there were no significant differences between cold tolerance of these larvae in different citrus types [oranges, Citrus sinensis (L.) Osbeck; grapefruits, Citrus paradisi Macfad.; lemons, Citrus limon (L.) Burm.f.; and mandarins). Due to their ready availability, 'Valencia' oranges were used in this study. When 62,492 larvae in total were treated in three replicates at a mean temperature of 1.5 degrees C for 16 d, there were three larval survivors. The trial was therefore repeated with oranges using a 16-d period at a mean temperature of 1.0 degrees C and a mean of 1.4 degrees C for the hourly maximum probe readings. Three replicates were again conducted and the resultant mean mortality in the control was 8.1% of 21,801 larvae, whereas the cold treatment mortality was 100% of 71,756 larvae. This treatment at a mean temperature of 1 degree C exceeded the Japanese confidence level requirement and also exceeded the Probit-9 mortality level, but not at a confidence level of 95%. These data support the establishment of a treatment protocol of 16 d at temperatures <1.4 degrees C, commencing once all fruit pulp probes reach a temperature of 1 degree C or lower.
南非目前使用在途冷处理方案，将新鲜柑橘（Citrus spp.）水果出口到日本，对于甜橙（Citrus reticulata Blanco）和其他柑橘类型中的地中海实蝇（Ceratitis capitata (Wiedemann)）（双翅目：实蝇科）分别采用 14 天或 12 天、温度低于 0°C 的处理方案。为了降低这种处理方案的冷害风险，南非开展了相关研究，温度超过 0°C。南非早期的研究表明，年幼（6 日龄）的幼虫对冷处理的耐受性略高，不同柑橘类型中的幼虫对冷处理的耐受性没有显著差异[橙子，Citrus sinensis (L.) Osbeck；葡萄柚，Citrus paradisi Macfad.；柠檬，Citrus limon (L.) Burm.f.；以及橘子]。由于它们易于获得，因此本研究使用了“瓦伦西亚”橙子。当总共 62,492 头幼虫在三个重复试验中以平均温度 1.5°C 处理 16 天时，有 3 头幼虫存活。因此，试验重复进行，在平均温度 1.0°C、每小时探头读数平均 1.4°C 的条件下，使用橙子处理 16 天。再次进行了三个重复试验，对照的死亡率平均为 21,801 头幼虫的 8.1%，而冷处理的死亡率为 71,756 头幼虫的 100%。这种平均温度为 1°C 的处理方案超过了日本置信水平要求，也超过了 Probit-9 死亡率水平，但置信水平为 95%时没有超过。这些数据支持建立一个 16 天的处理方案，在所有果实果肉探头温度达到 1°C 或以下时开始，温度<1.4°C。
