Insect pest occurrences on cabbage fields intercropped with leafy daikon, which is known to present a decoy plant for clubroot disease and belongs to the same family as cabbage (Brassicaceae), were examined at open field in the Miyagi prefecture, northern Japan. Four experiments were conducted to examine the influence of: intercropped leafy daikon’s seeding density on insect pest occurrence, trimming of intercropped leafy daikon on both insect pest occurrence and cabbage yield, and mix-cropping of leafy daikon and cabbage on insect pest occurrence. Leafy daikon intercropping reduced the occurrence of some insect pest species, especially that of the pests categorized as leaf-chewing pests, such as beet semi-loopers, Autographa nigrisigna Walker (Lepidoptera: Noctuidae), and small white butterflies, Pieris rapae crucivora Boisduval (Lepidoptera: Pieridae), and the results were compared with their occurrences in barley intercropping and non-intercropping. These two insect species were rarely observed on intercropped and mix-cropped leafy daikon, indicating it did not work as a trap crop. However, a reduction in cabbage yield due to shading of leafy daikon intercropping was observed, but the yield loss was mitigated by trimming of intercropped leafy daikon during the cultivation. Furthermore, leafy daikon intercropping with trimming had the same occurrence reduction effects against A. nigrisigna and P. rapae crucivora as leafy daikon intercropping without trimming. Our findings suggested that intercropping of closely related plants was possible by selecting the appropriate combinations of parameters and proper strategies, which proved to be useful for insect pest management in mix-cropping systems.

在日本北部宫城县的露天场地检查了白萝卜间作的害虫发生，白萝卜是根茎病的诱饵植物，与白菜（十字花科）属于同一科。进行了四项试验，研究了：间作多叶白萝卜的播种密度对病虫害发生的影响，间作多叶白萝卜修剪对病虫害发生和白菜产量的影响，以及多叶白萝卜和白菜混作对病虫害发生的影响。多叶白萝卜间作减少了一些害虫种类的发生，特别是被归类为嚼叶害虫的害虫，如甜菜半环虫、黑纹夜蛾（鳞翅目：夜蛾科）和小白蝴蝶，Pieris rapae crucivora Boisduval（鳞翅目：Pieridae），并将结果与​​它们在大麦间作和非间作中的发生情况进行比较。在间作和混作多叶白萝卜上很少观察到这两种昆虫，这表明它不能用作诱捕作物。然而，观察到由于间作多叶白萝卜的遮荫导致卷心菜产量下降，但在栽培期间修剪间作多叶白萝卜减轻了产量损失。此外，带修剪的多叶白萝卜间作对A. nigrisigna和P. rapae crucivora具有相同的减少发生效果作为没有修剪的多叶白萝卜间作。我们的研究结果表明，通过选择适当的参数组合和适当的策略，可以对密切相关的植物进行间作，这被证明对混作系统中的害虫管理很有用。