Refuge areas favor the presence of predators and herbivores in Bt soybean: a landscape perspective

Soybean plants that express various insecticidal proteins of the bacterium Bacillus thuringiensis have been widely adopted globally in many crop systems. This technology effectively controls the main defoliating pest species in most countries and reduces insecticide spray requirements. However, widespread use of Bt crops also generates high selection pressure against pest populations, leading to resistance concerns. Refuge areas are established to delay this phenomenon, but little is known about their other ecological functions. We evaluated the role of non-Bt soybean refuge areas regarding the abundance and richness of predator species in Bt soybean and non-Bt fields. For 2 years, herbivore and predatory arthropods were sampled in 28 soybean fields (RR/Bt) and their non-Bt soybean refuge areas (RR/noBt) in Uruguay, throughout the whole crop cycle. Landscape crop diversity (1 km radius) was characterized by its richness and evenness. Arthropod abundance and richness were analyzed using general linear mixed models. The abundance and richness of predators (Araneae, Coccinellidae, Heteroptera and Chrysopidae) found in Bt soybean were positively associated with the values recorded in refuge areas, independently of the diversity of the surrounding landscape. This relationship was not affected by changes in the distance between sampling points (within 800 m). The abundance of stink bugs and leaf-feeding caterpillars in Bt soybean was positively associated with refuge area values. Our results reinforce the importance of refuge areas, not only due to their role in resistance management, but also as preservation areas of beneficial fauna within a landscape approach to Integrated Pest Management in agroecosystems.