Complex Habitats Boost Predator Co-Occurrence, Enhancing Pest Control in Sweet Pepper Greenhouses

Sweet pepper is a crop that benefits from phytosanitary treatments with low environmental impact, especially the successful control of pests through the introduction of biological control agents in greenhouses. However, predators that naturally occur in these surroundings often enter greenhouses. The precise roles of these natural predators and their interactions with the introduced predatory insects and mites are often unknown. This study investigated the relationships between <i>Nesidiocoris tenuis</i>, which is naturally present, and <i>Amblyseius swirskii</i> and <i>Orius laevigatus</i>, which are two species of generalist predators released for the control of multiple pests. This study was conducted for two years on 13 commercial sweet pepper crops in various types of greenhouses (tunnels and traditional greenhouses) in Sicily. The environmental complexity value (ECV) for each site was estimated based on 18 points detected around the site according to the different habitats that occurred at each coordinate. The results showed that the occurrence of <i>N. tenuis</i> in greenhouses, independently of their typology (tunnel or traditional greenhouse), was mainly promoted by the greater diversification of habitats immediately surrounding the pepper crops (in a circular area with a diameter of 500 mt), with an increase in its density during the crop season. Moreover, <i>N. tenuis</i>–<i>O. laevigatus</i>’s co-occurrence in flowers suggested that they were not impacted by each other’s presence and that their co-occurrence had a significant effect on pest reduction, although their co-occurrence was density-dependent. As an intraguild predator, <i>N. tenuis</i> competed with <i>O. laevigatus</i> for <i>Frankliniella occidentalis</i> when many predators were present. In addition, <i>N. tenuis</i> also competed with <i>A. swirskii</i> when they both occurred in flowers at a higher density. This study highlights the importance of pepper plant flowers in promoting a higher occurrence of juvenile forms of <i>N. tenuis</i> within flowers. <i>Amblyseius swirskii</i> colonized the plants in 3 weeks, distributing itself almost uniformly over the leaves with a clear control action against not only <i>Bemisia tabaci</i> but also <i>F. occidentalis</i> when present on the flowers. Thus, this concurrent analysis of several commercial pepper sites within the same production area suggests that, even with similar pest control plans, the diverse variability in the presence of natural enemies must be considered when selecting control strategies for pepper crop pests and that <i>N. tenuis</i>, favored by complex surrounding habitats, contributes actively to pest reduction.