We investigated whether mowing the undergrowth in apple orchards affects the occurrence of spider mites and their predators, phytoseiid mites. We compared their occurrence between one unmown and one mown plot in an apple orchard in Akita Prefecture, northern Japan. Neither plot was mown in 2014 or 2015, but one plot was mown monthly from late May to late August in 2016 and 2017. Both plots were sprayed with narrow-spectrum insecticides in 2014 and 2015 and broad-spectrum insecticides in 2016 and 2017. In 2014 and 2015, some Tetranychus urticae were present on leaves in both plots, but their numbers did not increase greatly. In 2016, numbers of Panonychus ulmi and T. urticae surged in the mown plot, but grew slightly in the early growing season and then decreased in the unmown plot in association with rapid population increases of the predacious mites Typhlodromus vulgaris and Neoseiulus womersleyi. In 2017 also, numbers of T. urticae surged in the mown plot but remained low in the unmown plot. In addition, the numbers of T. vulgaris until July were significantly greater in the unmown plot in both years. Moreover, the population density of T. urticae when N. womersleyi began to appear was significantly lower in the unmown plot in both years. These results suggest that the resurgence of spider mites can be avoided by not mowing in apple orchards.

中文翻译：

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在苹果园使用广谱杀虫剂后，不进行割草可防止荨麻疹和全爪螨（Acari：Tetranychidae）的卷土重来

我们调查了修剪苹果园中的灌木丛是否会影响红蜘蛛及其天敌植物螨的发生。我们比较了它们在日本北部秋田县苹果园的一块未割草地块和一块已割草地块之间的发生情况。2014 年和 2015 年都没有割草，但在 2016 年和 2017 年的 5 月下旬至 8 月下旬每月割了一个地块。 两个地块都在 2014 年和 2015 年喷洒了窄谱杀虫剂，并在 2016 年和 2017 年喷洒了广谱杀虫剂。 2014 年和 2015 年，两个地块的叶子上都存在一些荨麻疹，但数量没有大幅增加。2016年，割草地块爪蟾和荨麻的数量激增，但在早期生长季节略有增长，然后在未割草的地块中随着捕食性螨类 Typhlodromus vulgaris 和 Neoseiulus womersleyi 种群的快速增加而减少。同样在 2017 年，割草地块中荨麻疹的数量激增，但未割地块中的荨麻疹数量仍然很少。此外，在这两年未割草的地块中，直到 7 月的 T. vulgaris 数量都明显增加。此外，在两年未割草的地块中，当 N. womersleyi 开始出现时，T. urticae 的种群密度显着降低。这些结果表明，在苹果园不割草可以避免红蜘蛛的卷土重来。在这两年的未割草地块中，直到 7 月的寻常型葡萄数量显着增加。此外，在两年未割草的地块中，当 N. womersleyi 开始出现时，T. urticae 的种群密度显着降低。这些结果表明，在苹果园不割草可以避免红蜘蛛的卷土重来。在这两年的未割草地块中，直到 7 月的寻常型葡萄数量显着增加。此外，在两年未割草的地块中，当 N. womersleyi 开始出现时，T. urticae 的种群密度显着降低。这些结果表明，在苹果园不割草可以避免红蜘蛛的卷土重来。