Department of Entomology and Nematology, University of California, Davis, CA.
Department of Ecology, Nanjing University, Nanjing, China.
J Econ Entomol. 2021 Feb 9;114(1):215-224. doi: 10.1093/jee/toaa258.
Sweet oranges (Citrus sinensis (L.) Osbeck Sapindales: Rutaceae) dominated commercial citrus production in California until recently when there has been a shift to mandarins, mostly Citrus reticulata (Blanco) mandarins and Citrus clementina (hort. ex Tanaka) clementines. Past analyses of commercial field scouting and harvest data indicated that fork-tailed bush katydids (Scudderia furcata Brunner von Wattenwyl), a major pest in oranges, are present in clementine groves, but that fruit scarring attributed to katydids is rare. Conversely, jagged or web-like scarring attributed to caterpillars was more prevalent than expected. We used two field experiments in four representative cultivars of clementines to test four explanatory hypotheses for this observation: 1) katydids do not feed on clementine fruit, 2) damaged clementine fruit recover, 3) damaged clementine fruit preferentially abscise, and 4) katydid scars on clementine fruit have a different, undocumented morphology, not recognized as katydid damage. We find support for the latter two hypotheses. Katydids fed readily on the clementine fruit of all cultivars tested, chewing irregular holes that developed into jagged or web-like scars of a range of shapes and often led to splitting and abscission of maturing fruit. The katydid scars often more closely resembled chewing caterpillar damage than the round katydid scars in oranges, suggesting that katydid damage is being misclassified in clementines. The resistance documented in some other mandarins was not observed. Katydids are clearly a frugivorous pest causing previously unrecognized scarring in clementines.
甜橙（Citrus sinensis (L.) Osbeck Sapindales: Rutaceae）曾在加利福尼亚州的商业柑橘生产中占主导地位，但最近这种情况发生了变化，主要种植品种为宽皮橘，包括甜橙（Citrus reticulata (Blanco)）和克莱门氏小柑橘（Citrus clementina (hort. ex Tanaka)）。过去对商业田间巡查和收获数据的分析表明，叉尾虫（Scudderia furcata Brunner von Wattenwyl）是橙子的主要害虫，它存在于克莱门氏小柑橘果园中，但归因于叉尾虫的果实疤痕很少见。相反，归因于毛毛虫的锯齿状或网状疤痕比预期更为普遍。我们在四个代表性的克莱门氏小柑橘品种中进行了两项田间实验，以检验对这一观察结果的四个解释性假设：1）叉尾虫不吃克莱门氏小柑橘果实，2）受损的克莱门氏小柑橘果实会恢复，3）受损的克莱门氏小柑橘果实优先脱落，4）克莱门氏小柑橘果实上的叉尾虫疤痕具有不同的、未记录的形态，未被识别为叉尾虫损伤。我们支持后两个假设。叉尾虫很容易就会吃掉我们测试的所有品种的克莱门氏小柑橘果实，它们会啃咬不规则的洞，这些洞会发展成各种形状的锯齿状或网状疤痕，而且常常导致成熟果实的开裂和脱落。叉尾虫的疤痕通常比橙子上的圆形叉尾虫疤痕更类似于咀嚼毛毛虫的损伤，这表明在克莱门氏小柑橘中，叉尾虫的损伤被错误分类。在其他一些宽皮橘中记录的抗性并没有被观察到。叉尾虫显然是一种以果实为食的害虫，它会在克莱门氏小柑橘中造成以前未被识别的疤痕。
