Maize as a companion plant in soybean fields: Implications for management of <i>Riptortus pedestris</i> (F.) (Hemiptera: Alydidae)

Abstract In South and East Asian countries, Riptortus pedestris (F.) (Hemiptera: Alydidae) is a major pest of soybean that causes significant yield losses. Chemical control remains the primary management strategy, but concerns over pesticide resistance and environmental impact underscore the need for sustainable alternatives. Companion planting has shown potential for pest suppression by modifying vegetation structure, influencing insect populations through top‐down and/or bottom‐up effects. This study investigated whether maize planted at soybean field edges could reduce major pest populations, including R. pedestris , and enhance biodiversity. Field experiments were conducted in seven small soybean fields, comparing monoculture soybean plots (four replicates) with those bordered by maize (three replicates). Arthropod densities were monitored from July to November 2022. The densities of R. pedestris nymphs and adults were significantly lower in maize treatment plots (peak: 0.37 per planting hole on 5 and 16 September, and 0.60 per planting hole on 7 October, respectively), than in control plots (peak: 0.74 and 1.13 per planting hole on 18 August, respectively). Furthermore, densities of whitefly (Hemiptera: Aleyrodidae) were also lower in maize treatment plots. However, the densities of other organisms, including herbivores and natural enemies, and their biodiversity or evenness indices did not significantly differ between treatments. These results suggest that maize may act as a physical or chemical barrier, limiting pest movement and reducing R. pedestris and whitefly densities through bottom‐up effects in soybean fields. Maize appears to be a promising companion plant for pest management in soybean cultivation.