Moore S D, Kirkman W, Albertyn S, Hattingh V
Citrus Research International, PO Box 20285, Humewood 6013, Port Elizabeth, South Africa (
Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa (
J Econ Entomol. 2016 Aug;109(4):1571-7. doi: 10.1093/jee/tow137. Epub 2016 Jun 24.
Some of South Africa's export markets require postharvest cold treatment of citrus fruit for phytosanitary risk mitigation for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to a standalone cold treatment may be a reduced intensity cold treatment as a step in a systems approach. For cold treatment trials, large numbers of larvae are required. Due to recent dramatic improvement of T. leucotreta control in the field, sufficient naturally infested citrus fruit are no longer available. Artificial infestation of fruit is not viable due to rapid decay of the fruit. Consequently, it is necessary to use laboratory-reared T. leucotreta larvae in artificial diet. In trials, field-collected larvae from the Eastern Cape were at least as cold-tolerant as those from other regions. Larvae in Navel oranges showed the median level of susceptibility in a range of citrus types evaluated at 6°C, and their use in trials was considered acceptable due to their greater natural susceptibility to T. leucotreta infestation. We demonstrated that larvae at high density in artificial diet were at least as cold-tolerant as larvae at lower densities. When exposed to 2°C for 18 d or longer, larvae in artificial diet as used in the trials were at least as cold-tolerant as larvae in fruit. Very few surviving larvae from fruit completed development, with no subsequent generation. Consequently, it is considered justifiable to conduct cold-treatment trials with laboratory-reared T. leucotreta larvae in artificial diet without risk of overestimating the effect of cold on feral larvae in citrus fruit. [corrected]
南非的一些出口市场要求对柑橘类水果进行采后冷处理，以降低 Thaumatotibia leucotreta（Meyrick）（鳞翅目：卷蛾科）带来的植物检疫风险。作为独立冷处理的替代方案，降低强度的冷处理可能是系统方法中的一个步骤。对于冷处理试验，需要大量幼虫。由于近期田间 T. leucotreta 的防治取得了显著进展，不再有足够数量自然感染的柑橘类水果。由于水果会迅速腐烂，对水果进行人工感染不可行。因此，有必要在人工饲料中使用实验室饲养的 T. leucotreta 幼虫。在试验中，从东开普省采集的田间幼虫至少与其他地区的幼虫一样耐冷。在 6°C 下评估的一系列柑橘品种中，脐橙中的幼虫表现出中等易感性水平，由于它们对 T. leucotreta 感染的天然易感性更高，因此在试验中使用它们被认为是可以接受的。我们证明，人工饲料中高密度的幼虫至少与低密度的幼虫一样耐冷。当暴露在 2°C 下 18 天或更长时间时，试验中使用的人工饲料中的幼虫至少与水果中的幼虫一样耐冷。从水果中存活下来的幼虫很少能完成发育，也没有后续世代。因此，用人工饲料中实验室饲养的 T. leucotreta 幼虫进行冷处理试验被认为是合理的，不会有高估寒冷对柑橘类水果中野生幼虫影响的风险。[已校正]
