Impact of soybean-buckwheat intercropping on phytophagous and beneficial arthropod communities in Northern Italy

Agricultural intensification and monoculture to address global population growth have progressively reduced the ecological integrity of agroecosystems, restricting the capacity of natural predators and arthropod communities to control pest populations. In the search for sustainable agricultural practices, intercropping and crop diversification have significantly contributed to enhancing biodiversity and pest suppression while reducing dependence on synthetic inputs. The resource concentration hypothesis explains how crop diversity can reduce pest pressure by decreasing host plant concentration and by supporting more abundant and diverse natural enemy populations. Soybean (Glycine max L.) is one of the most economically important crops in Northern Italy and worldwide. In the Veneto region, it is cultivated across 160,000 hectares with a production of around 545,000 tonnes per year. Among the key pests affecting soybean cultivation are the Brown Marmorated Stink Bug, Halyomorpha halys, and the Two-Spotted Spider Mite, T. urticae, both of which are polyphagous pests that can cause yield losses of up to 40–60% under favourable conditions. Due to its short life cycle, T. urticae can complete multiple generations within a single crop cycle, and as a result it is becoming resistant to acaricides, making chemical control increasingly difficult. Halyomorpha halys, also known as the Brown Marmorated Stink Bug, is an invasive pest in Europe and North America that attacks major crops including soybean, causing significant damage and losses of up to 30% if left uncontrolled. Current control strategies primarily rely on pyrethroids, which contradicts the EU Farm-to-Fork strategy of pesticide reduction and harms natural predators and pollinators. To reduce pesticide use, intercropping with a companion plant that promotes biological control is a viable option. Here we tested the effect of intercropping buckwheat (Fagopyrum esculentum) as a companion crop with soybean. Buckwheat was chosen because it has a short life cycle, rapid establishment, and low nutritional requirements, and its attractive flowers draw a wide range of beneficial organisms. A combination of soybean with buckwheat therefore offers a promising approach for managing and controlling several pests. This thesis project was conducted during the 2024–25 growing season across three sites in the Veneto region. The main experimental site was the Toniolo Farm at the Agripolis Campus in Legnaro, Padua, where a randomised block design with 40 plots of 12×12 metres was established. Four different intercropping configurations were compared: Frame (soybean surrounded by buckwheat), 2:1 (two rows of soybean alternating with one row of buckwheat), 1:1 (alternating rows of soybean and buckwheat), and soybean monoculture. The experiment was also conducted on two commercial farms in Chioggia and Vigonovo in the Veneto region to validate the results under real farming conditions. In Chioggia, soybean monoculture and the Frame configuration were established, while in Vigonovo the 2:1 and soybean monoculture configurations were used. The thesis focused on three major arthropod groups: pests (H. halys, N. viridula, and T. urticae), natural enemies (egg parasitoids and predatory mites), and pollinators. In all experiments, data were collected through repeated leaf and visual sampling throughout the season, and all collected specimens were identified using standard entomological procedures. Data analysis is still ongoing, but preliminary results show that intercropping buckwheat with soybean has a positive impact on pest reduction by promoting natural enemies, as well as a direct negative effect on pest populations across different intercropping configurations. This thesis will provide information for designing an innovative soybean cultivation model in the context of sustainable agriculture.